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  • 1.
    Aage, Hans
    Roskilde University, Denmark.
    25. Economic Instruments: Three Interlinkages Between Ecology and Economics2012Inngår i: Rural Development and Land Use / [ed] Lars Rydén and Ingrid Karlsson, Uppsala: Baltic University Press , 2012, 1, s. 280-293Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
    ehsa 3-25
  • 2.
    Aage, Hans
    Roskilde University, Denmark.
    51. The environment2002Inngår i: The Baltic Sea Region: Cultures, Politics, Societies / [ed] Witold Maciejewski, Uppsala: Baltic University Press , 2002, 1, s. 639-650Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
    BSR 8-51
  • 3. Aaro, Sven
    et al.
    Sjöström, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Airborne and ground geophysics used for regional tectonic analysis2003Inngår i: IUGG 2003, Sapporo, Japan: No GAV.06/10P/A11-004, B260., 2003Konferansepaper (Fagfellevurdert)
  • 4.
    Abadi, Mehrdad Sardar
    et al.
    Leibniz Inst Appl Geophys, LIAG, Rock Phys & Borehole Geophys, Hannover, Germany..
    Voeten, Dennis F. A. E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Kulagina, Elena, I
    Russian Acad Sci, Ufa Fed Res Ctr, Inst Geol, Ufa, Russia..
    Boulvain, Frederic
    Univ Liege, Dept Geol, Lab Petrol Sedimentaire, Bat B20, Liege, Belgium..
    Da Silva, Anne-Christine
    Univ Liege, Dept Geol, Lab Petrol Sedimentaire, Bat B20, Liege, Belgium..
    A comment on overlooked storm sensitivity of the carbonate factory recorded in the Mississippian Mobarak Formation (Alborz Mountains, Iran)2022Inngår i: Geological Journal, ISSN 0072-1050, E-ISSN 1099-1034, Vol. 57, nr 10, s. 4388-4392Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    New interpretations of depositional palaeoenvironments in the Mississippian (Lower Carboniferous) Mobarak Formation (Alborz Mountains, Iran) suggest a significant and persistent influence of storms. This deviates from previous conclusions that these deposits recorded mounds, patch reefs, and extensive lagoons deposited under stagnant environmental conditions. We here clarify and discuss the origin and nature of this misconception by explaining "unexpected" observations that are informed by outdated interpretations of the depositional environment of the Mobarak Formation. This evaluation offers the context required for appropriately interpreting and correlating Mississippian depositional records across the Alborz Basin.

  • 5.
    Abbasian, Maryam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    2D Reflection Seismic Imaging of Sparse 3D Data in the Zinkgruvan Mine, Central Sweden2021Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Zinkgruvan mining area in the southern Bergslagen mineral district of central Sweden holds over 30 million tons of massive sulphide mineralization. The ever-increasing global demand for mineral/metal resources, together with metal consumption growth especially for high-tech purposes has made the exploration of these resources of particular importance. In this thesis work, as a part of the larger research-industry SIT4ME project, Seismic Image Techniques for Mineral Exploration, project sponsored by the EIT Raw Materials, three 2D-crooked reflection seismic profiles were extracted from a sparse 3D dataset in the Zinkgruvan mining area and processed in a combination since approximately 600 receivers simultaneously recorded 368 shots along these three different profiles. One of the profiles (P1) was acquired using 10 m receiver and source intervals, while the other two profiles (P3 and P4) were acquired using 20 m receiver and 10 m source intervals. The data show notable reflections on several shot gathers presenting reasonable quality, although parts are severely contaminated with electricity grid noise from a major powerline crossing the profiles. The study mainly aims at providing information applicable for near surface structural imaging in this complex geological setting. Three different combinations of CDP lines for every two different profiles were binned and processed together in order to examine 3D nature of reflections and their corresponding geological origins. Through a number of tests and careful parameter selections, reflections in the raw shot gathers were enhanced. The final sections (both unmigrated and migrated stacks) show clear reflections associated with important geological units. This thesis presents the acquisition setup, reflection seismic processing procedure, results obtained and the interpretation of the three cross profiles in conjunction with available geological data from the site. The sections show a good correlation with the available borehole data from the site. 

    Fulltekst (pdf)
    fulltext
  • 6.
    Abbaszade, Yegana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Sustainability priorities of Swedish companies: an analysis of materiality matrixes2023Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
    Abstract [en]

    In this study, I used quantitative content analysis to analyze the materiality matrixes of sustainability reports to identify the sustainability priorities of major companies in Sweden. I focus on the 131 largest listed companies in the country within six industries: material, consumer goods, capital goods, daily goods, banks, and investment companies. The research questions include: (1) What are the primary focus areas of materiality for the largest listed companies in Sweden by industry? (2) On an overarching level, is the focus among all companies more environmental or social? (3) What are the primary applications of materiality analysis in the context of corporate decision-making in Sweden? The findings reveal that the primary materiality topics for Swedish companies are business ethics and climate impact. The focus is slightly more environmental, with 54% of companies having more of an environmental focus. Interestingly, only 22% of companies mentioned using materiality strategically, while a larger portion (40%) use materiality to identify their sustainability priorities. This research highlights the need for companies in Sweden to prioritize strategic sustainability in the face of new legislation, such as the Corporate Sustainability Reporting Directive (CSRD). Overall, this study demonstrates the value of analyzing materiality matrixes for identifying sustainability priorities in different industries and provides insights into using materiality analysis in corporate decision-making. The results can inform future sustainability strategies for Swedish companies and contribute to the broader conversation around sustainable business practices.

    Fulltekst (pdf)
    fulltext
  • 7.
    Abbott, Benjamin
    et al.
    Univ Rennes 1, OSUR, CNRS, ECOBIO,UMR 6553, Rennes, France.
    Baranov, Viktor
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Berlin, Germany.
    Mendoza-Lera, Clara
    Ctr LyonVilleurbanne, UR MALY, Irstea, F-69616 Villeurbanne, France.
    Nikolakopoulou, Myrto
    Naturalea, Barcelona, Spain.
    Harjung, Astrid
    Univ Barcelona, E-08007 Barcelona, Spain.
    Kolbe, Tamara
    Univ Rennes 1, CNRS, OSURGeosci Rennes, UMR 6118, F-35014 Rennes, France.
    Balasubramanian, Mukundh
    BioSistemika Ltd, Ljubljana, Slovenia.
    Vaessen, Timothy N
    CEAB CSIC, Girona, Spain.
    Ciocca, Francesco
    Silixa, Elstree, England.
    Campeau, Audrey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Wallin, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Romeijn, Paul
    Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands, England.
    Antonelli, Marta
    LIST, Esch Sur Alzette, Luxembourg.
    Goncalves, José
    Natl Inst Biol, Ljubljana, Slovenia.
    Datry, Thibault
    Ctr LyonVilleurbanne, UR MALY, Irstea, F-69616 Villeurbanne, France.
    Laverman, Anniet
    Univ Rennes 1, OSUR, CNRS, ECOBIO,UMR 6553, Rennes, France.
    de Dreuzý, Jean-Raynald
    Univ Rennes 1, CNRS, OSURGeosci Rennes, UMR 6118, F-35014 Rennes, France.
    David, Hannah M.
    Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands, England.
    Krause, Stefan
    Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands, England.
    Oldham, Carolyn
    Univ Western Australia, Civil Environm & Min Engn, Perth, WA, Australia.
    Pinay, Gilles
    Univ Rennes 1, OSUR, CNRS, ECOBIO,UMR 6553, Rennes, France.
    Using multi-tracer inference to move beyond single-catchment ecohydrology2016Inngår i: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 160, s. 19-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Protecting or restoring aquatic ecosystems in the face of growing anthropogenic pressures requires an understanding of hydrological and biogeochemical functioning across multiple spatial and temporal scales. Recent technological and methodological advances have vastly increased the number and diversity of hydrological, biogeochemical, and ecological tracers available, providing potentially powerful tools to improve understanding of fundamental problems in ecohydrology, notably: 1. Identifying spatially explicit flowpaths, 2. Quantifying water residence time, and 3. Quantifying and localizing biogeochemical transformation. In this review, we synthesize the history of hydrological and biogeochemical theory, summarize modem tracer methods, and discuss how improved understanding of flowpath, residence time, and biogeochemical transformation can help ecohydrology move beyond description of site-specific heterogeneity. We focus on using multiple tracers with contrasting characteristics (crossing proxies) to infer ecosystem functioning across multiple scales. Specifically, we present how crossed proxies could test recent ecohydrological theory, combining the concepts of hotspots and hot moments with the Damkohler number in what we call the HotDam framework.

    Fulltekst (pdf)
    fulltext
  • 8.
    Abbott, Benjamin W.
    et al.
    Univ Rennes 1, OSUR, CNRS, UMR ECOBIO 6553, F-35014 Rennes, France.;Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA.;Univ Alaska Fairbanks, Dept Biology& Wildlife, Fairbanks, AK USA..
    Jones, Jeremy B.
    Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA.;Univ Alaska Fairbanks, Dept Biology& Wildlife, Fairbanks, AK USA..
    Schuur, Edward A. G.
    No Arizona Univ, Ctr Ecosyst Sci & Soc, Flagstaff, AZ 86011 USA..
    Chapin, F. Stuart, III
    Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA.;Univ Alaska Fairbanks, Dept Biology& Wildlife, Fairbanks, AK USA..
    Bowden, William B.
    Univ Vermont, Rubenstein Sch Environm & Nat Resources, Burlington, VT 05405 USA..
    Bret-Harte, M. Syndonia
    Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA.;Univ Alaska Fairbanks, Dept Biology& Wildlife, Fairbanks, AK USA..
    Epstein, Howard E.
    Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA..
    Flannigan, Michael D.
    Univ Alberta, Dept Renewable Resources, Edmonton, AB T6G 2M7, Canada..
    Harms, Tamara K.
    Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA.;Univ Alaska Fairbanks, Dept Biology& Wildlife, Fairbanks, AK USA..
    Hollingsworth, Teresa N.
    Univ Alaska Fairbanks, PNW Res Stn, USDA Forest Serv, Fairbanks, AK USA..
    Mack, Michelle C.
    No Arizona Univ, Ctr Ecosyst Sci & Soc, Flagstaff, AZ 86011 USA..
    McGuire, A. David
    Univ Alaska Fairbanks, Alaska Cooperat Fish & Wildlife Res Unit, US Geol Survey, Anchorage, AK USA..
    Natali, Susan M.
    Woods Hole Res Ctr, Woods Hole, MA USA..
    Rocha, Adrian V.
    Univ Notre Dame, Dept Biol Sci, Notre Dame, IN 46556 USA.;Univ Notre Dame, Environm Change Initiat, Notre Dame, IN 46556 USA..
    Tank, Suzanne E.
    Univ Alberta, Dept Biol Sci, Edmonton, AB T6G 2M7, Canada..
    Turetsky, Merritt R.
    Univ Guelph, Dept Integrat Biol, Guelph, ON N1G 2W1, Canada..
    Vonk, Jorien E.
    Vrije Univ Amsterdam, Dept Earth Sci, Amsterdam, Netherlands..
    Wickland, Kimberly P.
    US Geol Survey, Natl Res Program, Boulder, CO USA..
    Aiken, George R.
    US Geol Survey, Natl Res Program, Boulder, CO USA..
    Alexander, Heather D.
    Mississippi State Univ, Forest & Wildlife Res Ctr, Mississippi State, MS 39762 USA..
    Amon, Rainer M. W.
    Texas A&M Univ, Galveston, TX USA..
    Benscoter, Brian W.
    Florida Atlantic Univ, Boca Raton, FL 33431 USA..
    Bergeron, Yves
    Univ Quebec Abitibi Temiscamingue, Forest Res Inst, Rouyn Noranda, PQ, Canada..
    Bishop, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära. wedish Univ Agr Sci, Dept Aquat Sci & Assessment, S-90183 Umea, Sweden..
    Blarquez, Olivier
    Univ Montreal, Dept Geog, Montreal, PQ H3C 3J7, Canada..
    Bond-Lamberty, Ben
    Pacific NW Natl Lab, Richland, WA 99352 USA..
    Breen, Amy L.
    Univ Alaska Fairbanks, Int Arctic Res Ctr, Scenarios Network Alaska & Arctic Planning, Fairbanks, AK USA..
    Buffam, Ishi
    Univ Cincinnati, Cincinnati, OH 45221 USA..
    Cai, Yihua
    Xiamen Univ, State Key Lab Marine Environm Sci, Xiamen, Peoples R China..
    Carcaillet, Christopher
    Ecole Prat Hautes Etud, UMR5023, CNRS Lyon 1, Lyon, France..
    Carey, Sean K.
    McMaster Univ, Hamilton, ON L8S 4L8, Canada..
    Chen, Jing M.
    Univ Toronto, Toronto, ON M5S 1A1, Canada..
    Chen, Han Y. H.
    Lakehead Univ, Fac Nat Resources Management, Thunder Bay, ON P7B 5E1, Canada..
    Christensen, Torben R.
    Lund Univ, Arctic Res Ctr, S-22100 Lund, Sweden.;Aarhus Univ, DK-8000 Aarhus C, Denmark..
    Cooper, Lee W.
    Univ Maryland, Ctr Environm Sci, Bethesda, MD USA..
    Cornelissen, J. Hans C.
    Vrije Univ Amsterdam, Syst Ecol, Amsterdam, Netherlands..
    de Groot, William J.
    Nat Resources Canada, Canadian Forest Serv, Toronto, ON, Canada..
    DeLuca, Thomas H.
    Univ Washington, Sch Environm & Forest Sci, Seattle, WA 98195 USA..
    Dorrepaal, Ellen
    Umea Univ, Dept Ecol & Environm Sci, Climate Impacts Res Ctr, S-90187 Umea, Sweden..
    Fetcher, Ned
    Wilkes Univ, Inst Environm Sci & Sustainabil, Wilkes Barre, PA 18766 USA..
    Finlay, Jacques C.
    Univ Minnesota, Dept Ecol Evolut & Behav, Minneapolis, MN 55455 USA..
    Forbes, Bruce C.
    Univ Lapland, Arctic Ctr, Rovaniemi, Finland..
    French, Nancy H. F.
    Michigan Technol Univ, Michigan Tech Res Inst, Houghton, MI 49931 USA..
    Gauthier, Sylvie
    Nat Resources Canada, Canadian Forest Serv, Laurentian Forestry Ctr, Toronto, ON, Canada..
    Girardin, Martin P.
    Nat Resources Canada, Canadian Forest Serv, Laurentian Forestry Ctr, Toronto, ON, Canada..
    Goetz, Scott J.
    Woods Hole Res Ctr, Woods Hole, MA USA..
    Goldammer, Johann G.
    Max Planck Inst Chem, Global Fire Monitoring Ctr, Berlin, Germany..
    Gough, Laura
    Towson Univ, Dept Biol Sci, Towson, MD USA..
    Grogan, Paul
    Queens Univ, Dept Biol, Kingston, ON K7L 3N6, Canada..
    Guo, Laodong
    Univ Wisconsin Milwaukee, Sch Freshwater Sci, Milwaukee, WI USA..
    Higuera, Philip E.
    Univ Montana, Dept Ecosyst & Conservat Sci, Missoula, MT 59812 USA..
    Hinzman, Larry
    Univ Alaska Fairbanks, Fairbanks, AK USA..
    Hu, Feng Sheng
    Univ Illinois, Dept Plant Biol, Chicago, IL 60680 USA.;Univ Illinois, Dept Geol, Chicago, IL 60680 USA..
    Hugelius, Gustaf
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden..
    Jafarov, Elchin E.
    Univ Colorado Boulder, Inst Arctic & Alpine Res, Boulder, CO USA..
    Jandt, Randi
    Univ Alaska Fairbanks, Alaska Fire Sci Consortium, Fairbanks, AK USA..
    Johnstone, Jill F.
    Univ Saskatchewan, Dept Biol, Saskatoon, SK S7N 0W0, Canada..
    Karlsson, Jan
    Umea Univ, Dept Ecol & Environm Sci, Climate Impacts Res Ctr, S-90187 Umea, Sweden..
    Kasischke, Eric S.
    Univ Maryland, Dept Geog Sci, Bethesda, MD USA..
    Kattner, Gerhard
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, Berlin, Germany..
    Kelly, Ryan
    Neptune & Co Inc, North Wales, PA USA..
    Keuper, Frida
    Umea Univ, Dept Ecol & Environm Sci, Climate Impacts Res Ctr, S-90187 Umea, Sweden.;INRA, AgroImpact UPR1158, New York, NY USA..
    Kling, George W.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Kortelainen, Pirkko
    Finnish Environm Inst, Helsinki, Finland..
    Kouki, Jari
    Univ Eastern Finland, Sch Forest Sci, Joensuu, Finland..
    Kuhry, Peter
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden..
    Laudon, Hjalmar
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, S-90183 Umea, Sweden..
    Laurion, Isabelle
    Inst Natl Rech Sci, Ctr Eau Terre Environm, Toronto, ON, Canada..
    Macdonald, Robie W.
    Inst Ocean Sci, Dept Fisheries & Oceans, Toronto, ON, Canada..
    Mann, Paul J.
    Northumbria Univ, Dept Geog, Newcastle Upon Tyne NE1 8ST, Tyne & Wear, England..
    Martikainen, Pertti J.
    Univ Eastern Finland, Dept Environm & Biol Sci, Joensuu, Finland..
    McClelland, James W.
    Univ Texas Austin, Inst Marine Sci, Austin, TX 78712 USA..
    Molau, Ulf
    Univ Gothenburg, Dept Biol & Environm Sci, Gothenburg, Sweden..
    Oberbauer, Steven F.
    Florida Int Univ, Dept Biol Sci, Miami, FL 33199 USA..
    Olefeldt, David
    Univ Alberta, Dept Revewable Resources, Edmonton, AB T6G 2M7, Canada..
    Pare, David
    Nat Resources Canada, Canadian Forest Serv, Laurentian Forestry Ctr, Toronto, ON, Canada..
    Parisien, Marc-Andre
    Nat Resources Canada, Canadian Forest Serv, No Forestry Ctr, Toronto, ON, Canada..
    Payette, Serge
    Univ Laval, Ctr Etud Nord, Quebec City, PQ G1K 7P4, Canada..
    Peng, Changhui
    Univ Quebec, Ctr CEF, ESCER, Montreal, PQ H3C 3P8, Canada.;Northwest A&F Univ, Coll Forestry, State Key Lab Soil Eros & Dryland Farming Loess P, Xian, Peoples R China..
    Pokrovsky, Oleg S.
    CNRS, Georesources & Environm, Toulouse, France.;Tomsk State Univ, BIO GEO CLIM Lab, Tomsk, Russia..
    Rastetter, Edward B.
    Marine Biol Lab, Ctr Ecosyst, Woods Hole, MA 02543 USA..
    Raymond, Peter A.
    Yale Univ, Sch Forestry & Environm Studies, New Haven, CT 06520 USA..
    Raynolds, Martha K.
    Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK USA..
    Rein, Guillermo
    Univ London Imperial Coll Sci Technol & Med, Dept Mech Engn, London SW7 2AZ, England..
    Reynolds, James F.
    Lanzhou Univ, Sch Life Sci, Lanzhou 730000, Peoples R China.;Duke Univ, Nicholas Sch Environm, Durham, NC 27706 USA..
    Robards, Martin
    Arctic Beringia Program, Wildlife Conservat Soc, New York, NY USA..
    Rogers, Brendan M.
    Woods Hole Res Ctr, Woods Hole, MA USA..
    Schaedel, Christina
    No Arizona Univ, Ctr Ecosyst Sci & Soc, Flagstaff, AZ 86011 USA..
    Schaefer, Kevin
    Univ Colorado Boulder, Cooperat Inst Res Environm Sci, Natl Snow & Ice Data Ctr, Boulder, CO USA..
    Schmidt, Inger K.
    Univ Copenhagen, Dept Geosci & Nat Resource Management, DK-1168 Copenhagen, Denmark..
    Shvidenko, Anatoly
    Int Inst Appl Syst Anal, A-2361 Laxenburg, Austria.;Sukachev Inst Forest, Moscow, Russia..
    Sky, Jasper
    Cambridge Ctr Climate Change Res, Cambridge, England..
    Spencer, Robert G. M.
    Florida State Univ, Dept Earth Ocean & Atmospher Sci, Tallahassee, FL 32306 USA..
    Starr, Gregory
    Univ Alabama, Dept Biol Sci, Tuscaloosa, AL 35487 USA..
    Striegl, Robert G.
    US Geol Survey, Natl Res Program, Boulder, CO USA..
    Teisserenc, Roman
    Univ Toulouse, CNRS, INPT, ECOLAB,UPS, Toulouse, France..
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Virtanen, Tarmo
    Univ Helsinki, Dept Environm Sci, FIN-00014 Helsinki, Finland..
    Welker, Jeffrey M.
    Univ Alaska Anchorage, Anchorage, AK USA..
    Zimov, Sergei
    Russian Acad Sci, Northeast Sci Stn, Moscow 117901, Russia..
    Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment2016Inngår i: Environmental Research Letters, E-ISSN 1748-9326, Vol. 11, nr 3, artikkel-id 034014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

    Fulltekst (pdf)
    fulltext
  • 9.
    Abboud, Sarah
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    The Role of Municipal Planning in the Permit Decisions on Large Onshore Wind Power Projects in Sweden2021Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Sweden wants to produce 100% of its electricity from renewable energy sources by 2040 and achieve net zero greenhouse gas emissions by 2045. While wind power is key to this transition, the permit process for large onshore wind power projects is one of the major challenges the country is currently facing, specifically the provision on municipal approval in the Environmental Code, the so-called municipal veto.

    To facilitate the expansion of wind projects in Sweden, the double testing of wind power applications was abolished in 2009, and the municipal veto was introduced to preserve the municipalities’ planning influence. However, the municipal veto contributed to a less predictable and legally secure permit process and became the main reason behind the rejections of wind power applications. Today, in 2021, the Swedish Government assigned a special investigator to examine and propose possible changes to the municipal veto provision.

    Though the municipalities believe that the veto is essential for their self-government and planning monopoly, the Swedish Energy Agency and the Swedish Environmental Protection Agency argue that the municipal authority should be exercised through the municipal general planning documents. Therefore, this thesis aims to verify the authorities’ argument by examining the relationship between the municipalities’ planning conditions for wind power and the permit decisions.

    The study is performed in collaboration with Westander Klimat och Energi and is based on 206 large onshore wind power applications between 2014 and 2020. The main research methods consist of a document analysis and of statistical analyses, namely simple percentages, and the chi-square test of independence, along with Cramer’s V calculation.

    The projects are categorized mainly based on the municipal planning conditions, and the permit decisions are analyzed accordingly. Essentially, it is shown that, even if not legally binding, the municipal general spatial planning documents constitute a valuable tool for the planning of onshore wind power projects in Sweden.

    Furthermore, the municipal planning conditions and permit decisions are not independent, however, their strength of association is weak. Nonetheless, the statistics indicate that in areas designated as suitable, more cases are likely to receive an approval than expected, and in areas not designated as suitable, the applications are more likely to be revoked than one would expect.

    In conclusion, it is important to invest resources into the strategic wind power planning at the local level. Also, the municipal plans must be kept updated to consistently reflect the municipalities’ intentions towards the use of their land and water areas.

    Fulltekst (pdf)
    fulltext
  • 10. Abbuehl, Luca M.
    et al.
    Norton, Kevin P.
    Schlunegger, Fritz
    Kracht, Oliver
    Aldahan, Ala
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Possnert, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandemlaboratoriet.
    El Niño forcing on 10Be-based surface denudation rates in the northwestern Peruvian Andes?2010Inngår i: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 123, nr 3-4, s. 257-268Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High magnitude precipitation events provide large contributions to landscape formation and surface denudation in arid environments. Here, we quantify the precipitation-dependent geomorphic processes within the Rio Piura drainage basin located on the Western Escarpment of the northern Peruvian Andes at 5 degrees S latitude. In this region, monsoonal easterly winds bring precipitation to the >3000 m asl high headwaters, from where the annual amount of precipitation decreases downstream toward the Pacific coast. Denudation rates are highest in the knickzones near the headwaters, similar to 200-300 mm ky(-1), and sediment discharge is limited by the transport capacity of the channel network. Every few years, this situation is perturbed by westerly, wind-driven heavy precipitation during El Nino events and results in supply-limited sediment discharge as indicated by bedrock channels. The detailed analysis of the stream-long profiles of two river basins within the Rio Piura catchment reveals a distinct knickzone in the transition zone between the easterly and westerly climatic influences, suggesting an En Nino forcing on the longitudinal channel profiles over at least Holocene timescales. Measured trunk stream catchment-wide denudation rates are up to ca. 300 mm ky(-1) and decrease successively downstream along the river profiles. Denudation rates of tributary rivers are ca. 200 mm ky(-1) near the plateau and show a stronger downstream decreasing trend than trunk stream rates. This suggests that the landscape is in a transient stage of local relief growth, which is driven by fluvial incision. This corroborates the results of paleoclimate studies that point towards higher El Nino frequencies during the past ca. 3000 years, leading to higher runoff and more erosion in the trunk channel compared to the hillslopes and thus growth of local relief. Downstream increases in channel gradient spatially coincide with the reaches of highest precipitation rates during El Nino events, we therefore interpret that Holocene landscape evolution has largely been controlled by climate. The ky-timescale of the Be-10 data together with the transience of the landscape implies that El Nino events in northwestern Peru have occurred since at least the Holocene, and that adjustment to channel incision is still taking place.

  • 11.
    Abdelmaksoud, Ahmed
    et al.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates.;Assiut Univ, Dept Geol, Assiut, Egypt..
    Ali, Mohammed Y.
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Al Suwaidi, Aisha
    Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Koyi, Hemin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Khalifa Univ Sci & Technol, Dept Earth Sci, Abu Dhabi, U Arab Emirates..
    Petroleum system of the fold-and-thrust belt of the United Arab Emirates: New insights based on 1D and 2D basin modeling2023Inngår i: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 158, artikkel-id 106567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydrocarbon potential of the fold-and-thrust belt (FTB) in the United Arab Emirates (UAE)-Oman mountains has received limited attention to date, leading to a poor understanding of the petroleum systems in this region. Despite the existence of hydrocarbon fields within the FTB, the source rock potential has not been adequately studied. This study aims to address this knowledge gap using 1D and 2D basin modeling approaches to evaluate the petroleum system of the FTB. In addition, gas chromatographs are also used to correlate hydrocarbon occurrences with their source rock. This study's findings identify the Silurian, Upper Cretaceous, Paleocene-Eocene, and Oligocene formations as the primary source rocks in the study area. Silurian shales, encountered in a well in the northern UAE, are currently considered overmature. The Cenozoic source rocks exhibit a spectrum of Total Organic Carbon (TOC) content, ranging from less than 1 to as high as 2 wt%, leading to variable degrees of expulsion efficiency. The maturity of these rocks varies based on their position in relation to the FTB and foredeep, with increasing maturity towards the north. The Upper Cretaceous sequences display low TOC and Hydrogen Index, indicating very low expulsion efficiency. The present-day distribution of maturity is largely influenced by Late Cretaceous and Oligocene-Miocene compressional events that affected the northern and northeastern Arabian Plate. This analysis shows that hydrocarbon expulsion from the Silurian source rocks was initiated during the Middle-Late Jurassic. These hydrocarbons are presumed to have migrated through Upper Permian, Jurassic, and Lower and middle Cretaceous reservoirs. Westward hydrocarbon migration, towards a regional bulge, may have also occurred following compressional events that resulted in lithospheric flexure and formation of the foreland basin. Notably, certain exceptions to migration towards the bulge include structural entrapment of hydrocarbons beneath the main frontal thrust zone of FTB and some structural traps beneath the Lower Fiqa Formation.

  • 12.
    Abdi, Amir
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Heinonen, Suvi
    Juhlin, Christopher
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Karinen, Tuomo
    Constraints on the geometry of the Suasselka post-glacial fault, northern Finland, based on reflection seismic imaging2015Inngår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 649, s. 130-138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unloading of the ice during the last glacial period in northern Fennoscandia is believed to have generated major faulting. These faults, often referred to as post-glacial faults, typically have clear surface exposures, but their geometry at depth is poorly known. In order to better understand the geometry at depth of the Suasselka post-glacial fault in Finland, three high resolution 2D reflection seismic profiles over the fault were reprocessed. Their total profile length is about 60 km and they were acquired as part of a major effort in Finland to map the uppermost crust in mining areas. The reprocessing led to significantly improved images that could be used to map the fault at depth. Two approximately N-S striking profiles and one E-W striking profile were reprocessed. The different azimuths and the crooked nature of the profiles allowed the fault geometry to be relatively well constrained. Clear reflections from the fault, dipping towards the SE, can be traced from the shallow subsurface down to about 3 km. The strike and dip of two sets of dipping reflections in the stacked data along with geometrical constraints and cross-dip analysis give a consistent dip of about 35-45 degrees towards the SE for the fault. The strike and dip vary from N55E with a dip of 35 degrees in the east to a strike of N48E with a dip of 45 degrees in the west. Existence of the two sets of reflections indicates that the fault surface is non-planar. Aside from allowing the geometry of the fault to be determined, the seismic data show a complex reflectivity pattern in the area and indications of both reverse and normal movement along fault planes with similar orientation to the Suasselka post-glacial fault. These images can be used as a basis for better characterizing the 3D geology of the area.

  • 13.
    Abdollahi, Somayeh
    et al.
    Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    Ardestani, Vahid Ebrahimzadeh
    Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    Zeyen, Hermann
    Univ Paris Saclay, Univ Paris Sud, CNRS, GEOPS, F-91405 Orsay, France.
    Shomali, Zaher Hossein
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    Crustal and upper mantle structures of Makran subduction zone, SE Iran by combined surface wave velocity analysis and gravity modeling2018Inngår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 747, s. 191-210Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The inversion of Rayleigh wave group velocity dispersion curves is challenging, because it is non-linear and multimodal. In this study, we develop and test a new Rayleigh wave dispersion curve inversion scheme using the Shuffled Complex Evolution (SCE) algorithm. Incorporating this optimization algorithm into the inverse procedure not only can effectively locate the promising areas in the solution space for a global minimum but also avoids its wandering near the global minimum in the final stage of search. In addition, our approach differs from others in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for thickness, velocities and densities and their vertical gradients of four layers, sediments, upper-crust, lower-crust and upper mantle. The proposed inverse procedure is applied to non-linear inversion of fundamental mode Rayleigh wave group dispersion curves for shear and compressional wave velocities. At first, to determine the efficiency and stability of the SCE method, two noise-free and two noisy synthetic data sets are inverted. Then real data for Makran region in SE Iran are inverted to examine the usage and robustness of the proposed approach on real surface wave data. In a second step, we applied 3D Gravity Modeling based on surface wave analysis results to obtain the density structure and thickness of each layer. The reason for using both types of data sets, is that gravity anomaly has a bad vertical resolution and surface wave group velocities are good for placing layer limits at depth, but they are not very sensitive to densities. Therefore, using gravity data increases the overall resolution of density distribution. In a final step, we used again the SCE method to invert the fundamental mode Rayleigh wave group dispersion curves based on the gravity results. Gravity results like thicknesses and sediment densities have been used to constrain the limit of search space in the SCE method. Results show a high shear and compressional velocity under the Gulf of Oman which reduce to the North of the Makran region. The Moho depth of the Oman Gulf is about 18-28 km and it increases to 46-48 km under the Taftan-Bazman volcanic-arc. The density image shows an average crustal density with maximum values under the Gulf of Oman decreasing northward to the Makran.

  • 14.
    Abdollahi, Somayeh
    et al.
    Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    Zeyen, Hermann
    Univ Paris Saclay, Univ Paris Sud, CNRS, GEOPS, F-91405 Orsay, France.
    Ardestani, Vahid Ebrahimzadeh
    Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    Shomali, Zaher Hossein
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Univ Tehran, Inst Geophys, POB 14155-6466, Tehran, Iran.
    3D joint inversion of gravity data and Rayleigh wave group velocities to resolve shear-wave velocity and density structure in the Makran subduction zone, south-east Iran2019Inngår i: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 173, s. 275-290Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we developed a method to invert jointly Rayleigh wave group velocities and gravity anomalies for velocity and density structure of the lithosphere. We applied the method to the Makran accretionary prism, SE Iran. The reason for using different data sets is that each of these data sets is sensitive to different parameters. Surface wave group velocities are sensitive mainly to shear wave velocity distribution in depth but do not well resolve density variations. Therefore, joint inversion with gravity data increases the resolution of density distribution. Our approach differs from others mainly in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for the properties of only four layers: thickness, P- and S-wave velocities and densities and their vertical gradients in sediments, upper-crust, lower-crust and upper mantle. The method is applied first to synthetic models in order to demonstrate its usefulness. We then applied the method to real data to investigate the lithosphere structure beneath the Makran. The resulting model shows that Moho depth increases from Oman Sea (18-33 km) and Makran fore-arc (33-37 km) to the volcanic-arc (44-46 km). The crustal density is high in the Oman Sea as should be expected for the oceanic crust. We also find a high-velocity anomaly in the upper mantle under the Oman Sea corresponding to the subducting slab. The crust under the fore-arc, volcanic-arc and back-arc settings of Makran subduction zone is characterized by low-velocity zones.

  • 15.
    Abdu, Y. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Annersten, H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Ericsson, T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Hawthorne, F. C.
    High-temperature cation ordering in olivine: an in situ Mossbauer study of synthetic (Mg0.55Fe0.45)(2) SiO42008Inngår i: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 186, nr 1-3, s. 99-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High- temperature in situ Mossbauer spectroscopy measurements ( 300 950. C) were done on synthetic olivine of composition ( Mg0.55Fe0.45) 2 SiO4 (= Fa45) in order to study the distribution of Fe2+ over the M1 and M2 octahedral sites. The spectra are fit with two doublets, which are assigned to Fe2+ at the M1 ( smaller splitting) and M2 sites. The Fe2+ site- occupancies at M1 and M2, obtained from the Mossbauer relative areas, suggest that Fe2+ has a slight preference for the M1 site at temperatures below similar to 500. C, with a tendency of disordering around this temperature. At higher temperatures, Fe2+ again prefers to occupy the M1 site, where it shows a considerable order at this site up to 750C. At still higher temperatures, the spectra indicated partial reduction of the Fa- component into metallic iron and the resolution of the doublets was severely deteriorated.

  • 16.
    Abdu, Yassir Ahmed Mohamed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Mössbauer Spectroscopy of Meteoritic and Synthetic Fe-Ni Alloys2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis reports on the results of investigating Fe-containing minerals in meteorites, with focus on Fe-Ni minerals and their magnetic properties, along with some synthetic Fe-Ni analogues. The New Halfa meteorite, which fell in Sudan 1994, has been studied using Mössbauer spectroscopy, X-ray diffraction, and electron microprobe analysis techniques, and classified as an ordinary L-type chondrite of petrologic type 4. Mössbauer spectra of taenite-enriched samples from the metal particles of the New Halfa (L4) and Al Kidirate (H6) meteorites identify the following γ (fcc) Fe-Ni phases: the ferromagnetic atomically ordered taenite (tetrataenite) with ~ 50 at % Ni, the ferromagnetic disordered taenite with ~ 50 at % Ni, the low-Ni (~ 25 at %) paramagnetic taenite (antitaenite). The presence of the superstructure of tetrataenite is confirmed by synchrotron X-ray diffraction.

    Fe-rich γ (fcc) Fe-Ni alloys with compositions Fe79Ni21, Fe76Ni24, and Fe73Ni27, which serve as synthetic analogues of antitaenite, are prepared by mechanical alloying and subsequent annealing at 650 °C. The Mössbauer results indicate that these alloys are inhomogeneous and contain a high moment (HM) ferromagnetic Ni-rich phase (> 30 at % Ni) and a low moment (LM) paramagnetic Fe-rich phase, which orders antiferromagnetically at low temperature. The coexistence of these phases is attributed to phase segregation occurring on short range, probably nanometer scale, consistent with the Fe-Ni phase diagram below 400 °C where there is a miscibility gap associated with a spinodal decomposition in alloys with < 50 at % Ni.

    The combined high field Mössbauer spectroscopy and SQUID magnetometry results on these alloys at room temperature indicate large induced local magnetic moments in the paramagnetic part of the sample, which increases with increasing the Ni content. The results, when compared with the high field Mössbauer results on antitaenite from the metal particle of Al Kidirate and New Halfa meteorites may be used to estimate the Ni content of antitaenite in meteorites.

    High pressure 57Fe Mössbauer spectroscopy measurements up to ~ 41 GPa have been carried out at room temperature using the diamond anvil cell (DAC) technique in order to investigate the magnetic properties of γ (fcc) 57Fe53Ni47 alloy. The results indicate a pressure induced Invar effect at ~ 7 GPa and a non-magnetic or paramagnetic state above 20 GPa, demonstrating the volume dependence of the magnetic moment of γ (fcc) Fe-Ni alloys.

    Delarbeid
    1. Mössbauer spectroscopy, X-ray diffraction and electron microprobe analysis of the New Halfa meteorite
    Åpne denne publikasjonen i ny fane eller vindu >>Mössbauer spectroscopy, X-ray diffraction and electron microprobe analysis of the New Halfa meteorite
    1997 Inngår i: Meteoritics and Planetary Science, Vol. 32, s. 373-375Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91276 (URN)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15bibliografisk kontrollert
    2. Mössbauer studies on the metallic phases of Al Kidirate and New Halfa Meteorites
    Åpne denne publikasjonen i ny fane eller vindu >>Mössbauer studies on the metallic phases of Al Kidirate and New Halfa Meteorites
    Vise andre…
    2002 Inngår i: Hyperfine Interactions C, Vol. 5, s. 375-378Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91277 (URN)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15bibliografisk kontrollert
    3. Coexisting antiferromagnetism and ferromagnetism in mechanically alloyed Fe-rich Fe-Ni alloys: Implications regarding the Fe-Ni phase diagram below 400 °C
    Åpne denne publikasjonen i ny fane eller vindu >>Coexisting antiferromagnetism and ferromagnetism in mechanically alloyed Fe-rich Fe-Ni alloys: Implications regarding the Fe-Ni phase diagram below 400 °C
    2004 (engelsk)Inngår i: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 280, nr 2-3, s. 395-403Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Fe–Ni alloys below the Invar region with compositions Fe100−xNix (x=21, 24, and 27 at%) were prepared by high-energy ball milling technique (mechanical alloying). The as-milled samples, characterized by X-ray diffraction and Mössbauer spectroscopy, contain a mixture of α (BCC) and γ (FCC) phases, whereas the samples annealed at 650°C for 0.5 h show a single γ (FCC) phase displaying a single line Mössbauer spectrum at room temperature (RT). At low temperature, the Mössbauer spectra of annealed Fe76Ni24 and Fe73Ni27 alloys show the existence of a magnetically split pattern together with a broad singlet, which are ascribed to a high-moment ferromagnetic Ni-rich phase and a low-moment Fe-rich phase, respectively. The Fe-rich phase in annealed Fe76Ni24 alloy, which is paramagnetic at RT, undergoes antiferromagnetic ordering at ∼40 K, estimated from the dramatic line broadening of its spectrum, giving rise to a small hyperfine field (e.g. ∼2 T at 6 K). The coexistence of these phases is attributed to phase segregation occurring in these alloys as a result of enhanced atomic diffusion. The stability of these alloys towards martensitic (FCC→BCC) transformation at low temperatures is discussed in connection with the Fe–Ni phase diagram below 400°C.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91278 (URN)10.1016/j.jmmm.2004.03.036 (DOI)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    4. Field induced local magnetic moments in gamma-fcc Fe-Ni anti-Invar alloys
    Åpne denne publikasjonen i ny fane eller vindu >>Field induced local magnetic moments in gamma-fcc Fe-Ni anti-Invar alloys
    2004 (engelsk)Inngår i: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 280, s. 243-250Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Mössbauer spectroscopy in longitudinal external fields (up to 7 T) and SQUID magnetometry (up to 5 T)measurements have been carried out on mechanically alloyed (MA) g (FCC) Fe100xNix (x ¼ 21; 24, and 27 at%) alloysat room temperature. The zero-field M.ossbauer spectra of these alloys show only singlets. The high field M.ossbauerresults indicate that large amounts of the material is in the paramagnetic state, giving rise to two spectral componentswith their effective fields almost linearly depend on the external field, but with slopes that are smaller than unity. The infieldM.ossbauer spectra of the x ¼ 27 at% alloy show an additional component with a hyperfine field of E21 T, whichis attributed to Ni-rich (>30 at% Ni) clusters (domains) of ferromagnetically ordered HM phase that behavessuperparamagnetically at room temperature and shows a non-linear character in the magnetization (M–H) curves atlow fields. This HM phase is also present in the x ¼ 21 and 24 at% samples but with smaller amounts. The resultssuggest induced hyperfine fields and hence induced moments in the paramagnetic components, which increases withincreasing Ni contents. Taenite-enriched samples from the metal particles of two stony meteorites, Al Kidirate (H6)and New Halfa (L4), are also studied by high field M.ossbauer spectroscopy and the results are compared to that ofMA samples.

    Emneord
    Mössbauer spectroscopy; External field; Magnetization; Fe–Ni alloys; Antitaenite
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91279 (URN)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    5. Non-magnetic stainless steels reinvestigated: A small effective field component in external magnetic fields
    Åpne denne publikasjonen i ny fane eller vindu >>Non-magnetic stainless steels reinvestigated: A small effective field component in external magnetic fields
    2004 (engelsk)Inngår i: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 156/157, s. 151-155Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Three standard non-magnetic stainl ess steels of composition (wt%) Fe 70 Cr 19 Ni 11 , Fe 70 Cr 17 Ni 13 and Fe 69 Cr 18 . 5 Ni 10 . 3 Mn 1 . 8 Ti 0 . 4 have been investigated by Mössbauer spectroscopy (5–295 K and in external fields 7 T at room temperature) and ma gnetization measurements (10– 300 K) using a SQUID magnetometer. There are indications of a field induced ferromagnetic inter- action in the samples at room temperature

    Emneord
    stainless steel, external field, field induced ferromagnetism
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91280 (URN)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    6. High pressure Mössbauer studies on fcc Fe53Ni47 alloy
    Åpne denne publikasjonen i ny fane eller vindu >>High pressure Mössbauer studies on fcc Fe53Ni47 alloy
    2004 (engelsk)Inngår i: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 156, s. 394-, artikkel-id 389Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91281 (URN)10.1007/978-1-4020-2852-6_59 (DOI)
    Tilgjengelig fra: 2004-01-15 Laget: 2004-01-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    Fulltekst (pdf)
    FULLTEXT01
  • 17.
    Abdulrahman, Akram
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. 19931115.
    Evaluating the Role of Energy Policy for Electrification in Ethiopia2021Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Access to electricity is a scarcity throughout sub-Saharan African countries. The region currently has the lowestrate of energy access in the world and a total of 13 countries have an electrification rate of 25%. Comprehensiveenergy security is regarded as essential to obtaining sustainable and economic development in which access toaffordable and clean energy is part of the Sustainable Development Goals of the United Nations Agenda 2030.A country in the region that has had some sporadic success with electrification and unique developments withrenewable energy, is Ethiopia. Despite the significant overall increase of access to electricity over the past twodecades, the country still has an electrification rate that barely covers half of the population. An aspect that isviewed to have an impact on increased electrification and successful transitioning of deploying renewableenergy, is the use and presence of strong policies. Several researchers and scholars have explored the effect thatpolicy has on increased electrification and how they are useful for promoting renewable energy. This researchaims to investigate the role of policy for electrification via renewables in Ethiopia. The objective of the thesisis to explore sustainable development in terms of energy development, how climate change and economicdevelopment is tackled, and what specific influences shape the energy outlook of Ethiopia. A case study wasconducted which combined two different methods; content analysis of policy documents and semi-structuredinterviews with experts from various fields in which the data was triangulated in order to gain valuableperspectives and insights. The findings showcase that policy developments do seem to have an influence onincreased electrification and sustainable energy transitioning to some extent, with other factors also playing arole. Thus, this research will contribute to how sustainable development can be understood from the context ofenergy policy of a global south nation and provide insights which can further be elaborated on how policies canbe utilized for successful energy developments in other countries in the region.

    Fulltekst (pdf)
    fulltext
  • 18.
    Abdurahmanov, Fagan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    BUILDING A SUSTAINABLE FUTURE WITH WIND ENERGY: AZERBAIJAN’S AMBITIOUS PLANS FOR KARABAKH2023Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Transitioning to renewable energy is critical for reaching global sustainable development goals. As an oil-rich country, Azerbaijan has recognized the need to develop its renewable energy sector. It has set ambitious goals for increasing the share of renewables in its energy mix and establishing a green energy zone in the Karabakh region. The purpose of this master's thesis is to assess the potential of wind energy in Azerbaijan's Karabakh region and surrounding areas and identify the best scenario for its development. Four scenarios were evaluated via the PROMETHEE II Multi-Criteria Decision Analysis (MCDA) method based on their economic, environmental, technological, and social factors. Interviews with real stakeholders were undertaken to elicit weights for the criteria, and a sensitivity analysis was conducted to evaluate the robustness of the results. The findings were shared with the stakeholders, and their input was integrated into the final analysis. According to the findings, Scenario 4, which includes more installed capacity and increased investment, is best suited for the growth of wind energy in the Karabakh and surrounding areas from the perspective of developer and governmental body. In contrast, renewable energy expert and the public prefer Scenario 1, with less land use and less capacity. The findings indicate that for the effective development of wind energy in the area, a balanced approach taking into account the opinions of all stakeholders, is essential. This study contributes to Azerbaijan's long-term development by offering valuable insights into the potential of wind energy in the Karabakh region and surrounding areas and supporting informed decision-making for its expansion.

    Fulltekst (pdf)
    fulltext
  • 19.
    Abegunawardana, Sidath
    et al.
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Bodhika, J A P
    Univ Ruhuna, Dept Phys, Matara, Sri Lanka.
    Abewardhana, Ruwan
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Fernando, Mahendra
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sound Source Localization of Lightning Discharges2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The lightning channel can be retraced by thunder signature recorded with an array of microphones. Four microphones were arranged to capture thunder sound, and acoustic cross-correlation of captured pressure signals estimated the time lag of each pair of microphones. A wave segment with 0.25 s or 0.5 s of duration was compared with the acoustic signal recorded by other microphones to estimate time lapse. The direction of channel propagation has been estimated by the time difference of arrival of each pair of microphones. Thunder source locations estimated by this method can be extended to investigate the channel propagation inside clouds.

  • 20.
    Abegunawardana, Sidath
    et al.
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Bodhika, J A P
    Univ Ruhuna, Dept Phys, Matara, Sri Lanka.
    Nanayakkara, Sankha
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Sonnadara, Upul
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Fernando, Mahendra
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Audible Frequency Analysis of Ground Flashes2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Thunder signatures categorized into three types based on peak pressure and variation in fundamental frequency, have been studied by using acoustic spectrum of thunder. S-transformation has been used to estimate the dominant frequency variation around the peak pressure. The mean fundamental frequencies of type 3 ground and cloud flashes are 160 Hz and 98 Hz respectively. The mean frequencies of type 2 ground and cloud flashes are 108 Hz and 82 Hz respectively.

  • 21. Abernethy, R.
    et al.
    Weyhenmeyer, Gesa A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Ziese, Markus G.
    State of the Climate in 20172018Inngår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 99, nr 8, s. Si-S310Artikkel i tidsskrift (Fagfellevurdert)
  • 22.
    Abewardhana, Ruwan
    et al.
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Abegunawardana, Sidath
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Fernando, Mahendra
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Sonnadara, Upul
    Univ Colombo, Dept Phys, Colombo, Sri Lanka.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lightning Localization Based on VHF Broadband Interferometer Developed in Sri Lanka2018Inngår i: 2018 34th international conference on lightning protection (ICLP 2018), New York: IEEE, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A basic broadband digital interferometer was developed, which is capable of locating Very High Frequency (VHF) radiation sources in two spatial dimensions and time. Three antennas sensed the time series of broadband electromagnetic (EM) signals and digitized with 4 ns sampling interval for a duration of several milliseconds. A technique based on cross-correlations has been implemented for mapping lightning source locations. A map of the first return stroke (RS) and the preceding stepped leader was mapped successfully, using the system with a time resolution of few milliseconds. The result was compared with the visible events of the ground flash to validate the system.

  • 23.
    Abeysinghe, Kasun S.
    et al.
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550081, Guizhou, Peoples R China.;Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China.;Guangxi Univ, Coll Forestry, Guangxi Key Lab Forest Ecol & Conservat, 100 Daxue Rd,Coll Forestry Off 519, Nanning 530005, Guangxi, Peoples R China.;Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China..
    Qiu, Guangle
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550081, Guizhou, Peoples R China..
    Goodale, Eben
    Guangxi Univ, Coll Forestry, Guangxi Key Lab Forest Ecol & Conservat, 100 Daxue Rd,Coll Forestry Off 519, Nanning 530005, Guangxi, Peoples R China..
    Anderson, Christopher W. N.
    Massey Univ, Inst Agr & Environm, Soil & Earth Sci, Palmerston North 4442, New Zealand..
    Bishop, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Lennart Hjelmsvag 9, SE-75007 Uppsala, Sweden..
    Evers, David C.
    Biodivers Res Inst, 276 Canco Rd, Portland, ME 04103 USA..
    Goodale, Morgan W.
    Biodivers Res Inst, 276 Canco Rd, Portland, ME 04103 USA..
    Hintelmann, Holger
    Trent Univ, Chem Dept, 1600 West Bank Dr, Peterborough, ON K9J 7B8, Canada..
    Liu, Shengjie
    Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China.;Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China..
    Mammides, Christos
    Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China..
    Quan, Rui-Chang
    Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China..
    Wang, Jin
    Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China.;Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China..
    Wu, Pianpian
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Lennart Hjelmsvag 9, SE-75007 Uppsala, Sweden..
    Xu, Xiao-Hang
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550081, Guizhou, Peoples R China.;Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China..
    Yang, Xiao-Doug
    Chinese Acad Sci, Key Lab Trop Forest Ecol, Xishuangbanna Trop Bot Garden, Mengla 666303, Yunnan, Peoples R China..
    Feng, Xinbin
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550081, Guizhou, Peoples R China..
    Mercury flow through an Asian rice-based food web2017Inngår i: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 229, s. 219-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mercury (Hg) is a globally-distributed pollutant, toxic to humans and animals. Emissions are particularly high in Asia, and the source of exposure for humans there may also be different from other regions, including rice as well as fish consumption, particularly in contaminated areas. Yet the threats Asian wildlife face in rice-based ecosystems are as yet unclear. We sought to understand how Hg flows through rice-based food webs in historic mining and non-mining regions of Guizhou, China. We measured total Hg (THg) and methylmercury (MeHg) in soil, rice, 38 animal species (27 for MeHg) spanning multiple trophic levels, and examined the relationship between stable isotopes and Hg concentrations. Our results confirm biomagnification of THg/MeHg, with a high trophic magnification slope. Invertivorous songbirds had concentrations of THg in their feathers that were 15x and 3x the concentration reported to significantly impair reproduction, at mining and non-mining sites, respectively. High concentrations in specialist rice consumers and in granivorous birds, the later as high as in piscivorous birds,, suggest rice is a primary source of exposure. Spiders had the highest THg concentrations among invertebrates and may represent a vector through which Hg is passed to vertebrates, especially songbirds. Our findings suggest there could be significant population level health effects and consequent biodiversity loss in sensitive ecosystems, like agricultural wetlands, across Asia, and invertivorous songbirds would be good subjects for further studies investigating this possibility.

  • 24.
    Abeysinghe, Kasun S.
    et al.
    Chinese Acad Sci, Xishuangbanna Trop Bot Garden, Key Lab Trop Forest Ecol, Mengla, Yunnan, Peoples R China.;Univ Chinese Acad Sci, Beijing, Peoples R China..
    Yang, Xiao-Dong
    Chinese Acad Sci, Xishuangbanna Trop Bot Garden, Key Lab Trop Forest Ecol, Mengla, Yunnan, Peoples R China..
    Goodale, Eben
    Guangxi Univ, Coll Forestry, Nanning, Guangxi, Peoples R China..
    Anderson, Christopher W. N.
    Massey Univ, Inst Agr & Environm, Soil & Earth Sci, Palmerston North, New Zealand..
    Bishop, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Cao, Axiang
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang, Peoples R China.;Guizhou Normal Univ, Sch Chem & Mat Sci, Guiyang, Peoples R China..
    Feng, Xinbin
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang, Peoples R China..
    Liu, Shengjie
    Chinese Acad Sci, Xishuangbanna Trop Bot Garden, Key Lab Trop Forest Ecol, Mengla, Yunnan, Peoples R China.;Univ Chinese Acad Sci, Beijing, Peoples R China..
    Mammides, Christos
    Chinese Acad Sci, Xishuangbanna Trop Bot Garden, Key Lab Trop Forest Ecol, Mengla, Yunnan, Peoples R China..
    Meng, Bo
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang, Peoples R China..
    Quan, Rui-Chang
    Chinese Acad Sci, Xishuangbanna Trop Bot Garden, Key Lab Trop Forest Ecol, Mengla, Yunnan, Peoples R China..
    Sun, Jing
    Nanjing Agr Univ, Coll Resources & Environm Sci, Nanjing, Jiangsu, Peoples R China..
    Qiu, Guangle
    Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang, Peoples R China..
    Total mercury and methylmercury concentrations over a gradient of contamination in earthworms living in rice paddy soil2017Inngår i: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 36, nr 5, s. 1202-1210Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mercury (Hg) deposited from emissions or from local contamination, can have serious health effects on humans and wildlife. Traditionally, Hg has been seen as a threat to aquatic wildlife, because of its conversion in suboxic conditions into bioavailable methylmercury (MeHg), but it can also threaten contaminated terrestrial ecosystems. In Asia, rice paddies in particular may be sensitive ecosystems. Earthworms are soil-dwelling organisms that have been used as indicators of Hg bioavailability; however, the MeHg concentrations they accumulate in rice paddy environments are not well known. Earthworm and soil samples were collected from rice paddies at progressive distances from abandoned mercury mines in Guizhou, China, and at control sites without a history of Hg mining. Total Hg (THg) and MeHg concentrations declined in soil and earthworms as distance increased from the mines, but the percentage of THg that was MeHg, and the bioaccumulation factors in earthworms, increased over this gradient. This escalation in methylation and the incursion of MeHg into earthworms may be influenced by more acidic soil conditions and higher organic content further from the mines. In areas where the source of Hg is deposition, especially in water-logged and acidic rice paddy soil, earthworms may biomagnify MeHg more than was previously reported. It is emphasized that rice paddy environments affected by acidifying deposition may be widely dispersed throughout Asia.

  • 25.
    Abiodun, B. and Enger, L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    The role of advection of fluxes on modelling dispersion in convective boundary2002Inngår i: Quart. J. Roy. Met. Soc., Vol. 128, s. 1589-1607Artikkel i tidsskrift (Fagfellevurdert)
  • 26.
    Abirifard, Mahmoud
    et al.
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Raeisi, Ezzat
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Zarei, Mehdi
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Zare, Mohammad
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Filippi, Michal
    Czech Acad Sci, Inst Geol, Vvi, Rozvojova 269, Prague 6, Czech Republic..
    Bruthans, Jiri
    Charles Univ Prague, Fac Sci, Albertov 6, Prague 12843 2, Czech Republic..
    Talbot, Christopher J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Jahani Salt Diapir, Iran: hydrogeology, karst features and effect on surroundings environment2017Inngår i: International Journal of Speleology, ISSN 0392-6672, E-ISSN 1827-806X, Vol. 46, nr 3, s. 445-457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Jahani Salt Diapir (JSD), with an area of 54 km(2), is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir.

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  • 27. Abouessa, A.
    et al.
    Morad, S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    An integrated study of diagenesis and depositional facies in tidal sandstones: Hawaz Formation (middle Ordovician), Murzuq Basin, Libya2009Inngår i: Journal of Petroleum Geology, ISSN 0141-6421, E-ISSN 1747-5457, Vol. 32, nr 1, s. 39-65Artikkel i tidsskrift (Fagfellevurdert)
  • 28.
    Abrahamsson, Elin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Sveriges lantbruksuniversitet.
    In situ-metoder för sanering av klorerade lösningsmedel: utvärdering med avseende på svenska förhållanden2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    I nuläget finns det 428 områden registrerade som förorenade med klorerade lösningsmedel iSverige. Dessa ämnen har använts inom svensk industri som avfettnings- och lösningsmedelsedan 1930-talet. Klorerade lösningsmedels komplexa spridningsbild medför större svårigheter vid sanering och undersökning jämfört med exempelvis petroleumkolväten. Därför är det viktigt att öka kunskapen om sanering av lösningsmedel. En flitigt användsaneringsmetod av förorenade områden i Sverige är schaktsanering. Där grävs jord upp för att sedan transporteras till behandlingsanläggning eller deponi. På grund av metodens klimat- och miljöpåverkan behöver saneringsmetoder som är mer ekonomiskt och miljömässigt hållbaratillämpas oftare.

    Detta examensarbete syftade till att utvärdera in situ-saneringsmetoder för mark och grundvatten förorenade av klorerade lösningsmedel utifrån funktions-, tids-, hållbarhets- och kostnadsaspekter. Vidare syftade arbetet till att undersöka vilka metoder som lämpar sig bäst under svenska förhållanden. För att utvärdera in situ-metoders lämplighet och olika funktionsaspekter beskrevs lämpliga in situ-metoder. En fallstudie genomfördes där fem områden förorenade med klorerade lösningsmedel runtom i Sverige studerades. För samtliga områden beskrevs området och föroreningssituationen. Därefter presenterades konsulternas utvärdering och val av saneringsmetod samt resultat av utförd sanering. Metoder som studerades i fallstudien var två tekniker tillhörande kemisk reduktion, multifasextraktion,biostimulering och termisk behandling. De fem projekten värderades även med SGI:s beslutstödsverktyg för saneringsmetoder, SAMLA. Där poängsattes metoderna utifrån olika kriterier tillhörande miljö, sociala faktorer samt ekonomi. Vidare gjordes en allmän utvärdering av in situ-metoder för klorerade lösningsmedel utifrån svenska förhållanden, vad gäller geologi, hydrogeologi, geokemi och klimat. De utvärderades även utifrån dess styrkor och svagheter med avseende på tillämpningsområden, kostnad, saneringstid,energiförbrukning samt användning i Sverige som sammanställdes i matriser.

    Värderingen i SAMLA av de fem projekten visade på liknande resultat jämfört med tidigare genomförda riskvärderingar. De metoder som valdes i riskvärderingarna fick även högst tilldelad poäng i SAMLA. Valet av metod för respektive projekt valdes utifrån rådande förhållanden på området, såsom geologi och befintliga byggnader. Slutsatser som kan drasfrån detta arbete är att samtliga in situ-metoder som utvärderades kan tillämpas i Sverige utifrån de geologiska förhållandena. Däremot är det de platsspecifika förhållandena, såsom stort grundvattenflöde eller heterogen jord, som styr valet av saneringsmetod. Även förutsättningar för fastigheten måste beaktas, exempelvis byggnader på platsen eller exploatering av området. Dock kan tillämpningen av in situ-metoder eventuellt utvecklas mo ten viss typ av geologiska förhållanden (högpermeabla jordar) där klorerade lösningsmedel troligen kan påträffas oftare.

    Fulltekst (pdf)
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  • 29.
    Abrahamsson, Elin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Ekelund, My
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Human Exposure from Mercury in Rice in the Philippines2015Student paper other, 10 poäng / 15 hpOppgave
    Abstract [en]

    In the western part of the Philippines, in the Palawan province, studies have shown that large quantities of mercury are spread to the surrounding area during heavy rainfall. In addition, mercury is spread to rice fields and bioaccumulated in marine fish and seafood. The mercury originates from the abandoned Palawan Quicksilver Mine. Since mercury is toxic for the human body and new studies have shown that mercury accumulates in rice, it is important to investigate human exposure from mercury in rice.

    This project investigates the total amount of mercury and methylmercury (MeHg) accumulated in rice, soil and water from four different rice fields in Palawan. The soil samples have been taken directly from the fields and water samples have been taken from nearby streams and springs. Rice grains harvested earlier this year from the same fields have been collected from farmers. The soil, water and rice samples were analyzed in Manila and rice samples were as well analyzed in Sweden and China. Furthermore, this project contains a dietary survey and calculation of daily exposure values of MeHg. The survey investigates how often people eat fish and rice and if they have dental amalgam. It also investigates possible health problems related to mercury exposure from rice and fish consumption.

    The analyses from China show that rice samples from all barangays contain total mercury and MeHg. Analyses from Sweden also show that rice from the barangays contains total mercury but the levels were found to be higher than the ones analyzed in China. Furthermore, the health problems found in the diet survey were hard to relate to mercury exposure from rice since the health problems can be caused by other factors. When calculating daily exposure values, the values were found to be as high as the recommended maximum acceptable daily intake in one of the barangays. There might therefore be a risk of eating rice from these four barangays. It is important to consider that these daily exposure values were only based on MeHg exposure from rice consumption, not taking dental amalgam and fish consumption into consideration. This means that the daily exposure values might be even higher than the ones calculated in this study.

    Fulltekst (pdf)
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  • 30.
    Abrahamsson, Kristina
    Institutionen för Energi och Teknik, Sveriges Lantbruksuniversitet.
    Analys av olika metoder för att uppskatta olika livsmedels effekt på kvävecykeln2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Intensifiering av jordbruket globalt har lett till förhöjda halter reaktivt kväve (Nr) i omlopp på jorden. Användningen av stora mängder av framförallt handelsgödselkväve har rubbat balansen mellan reaktivt kväve och icke reaktivt kväve i kvävecykeln, vilket orsakar stora problem i form av övergödning. För att motverka denna negativa miljöpåverkan är det viktigt att uppmärksamma både makthavare och konsumenter på problemen och redovisa vilken påverkan som sker vid produktion av olika livsmedel. Detta så att konsumenter har möjlighet göra hållbara val vid köp av livsmedel och så att ett hållbart jordbruk kan utvecklas. För att beräkna ett livsmedels påverkan på kvävecykel kan flera olika metoder användas. I denna studie analyseras indikatorerna kväveffektivitet (NUE), kvävefotavtryck samt övergödningspotential för att undersöka vilken av indikatorerna som lämpar sig bäst för konsumentvägledning. NUE definieras som Nut/Nin och beräknar hur stor andel av inflödet av N som kommer ut i slutprodukten. Kvävefotavtrycket beräknas som (Nin-Nut) per kg produkt och övergödningspotential som utsläpp av olika övergödande ämnen per kg produkt. Indikatorerna applicerades på olika svenska livsmedel samt sojabönor från Brasilien och resultatet visade på att högst övergödningspotential och kvävefotavtryck fås för kött från kyckling, gris och nötkreatur. För samma indikatorer beräknades lägst potential och fotavtryck för gurka, tomat och morot. NUE beräknades vara högst för gurka på 0,90 och lägst för hallon och jordgubbe på 0,05 samt 0,08. Vid jämförelse av indikatorerna fastställdes att kvävefotavtrycket är bäst lämpad för konsumentvägledning eftersom resultatet är lättförståeligt och det kan kopplas till specifika miljöproblem så som övergödning. Övergödningspotentialen är också en lättförståelig indikator men N som resurs analyseras inte. Indikatorn kräver också mycket data som kan vara svår att få tag på för produkter som produceras i andra länder. Resultatet av NUE är lite mer komplicerat och indikatorn kan passa bättre som ett mått på hur kväveeffektivt en gård eller land är och därav lämpar sig indikatorn bättre för bönder och makthavare än konsumenter.

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  • 31. Abramoff, Rose Z.
    et al.
    Georgiou, Katerina
    Guenet, Bertrand
    Torn, Margaret S.
    Huang, Yuanyuan
    Zhang, Haicheng
    Feng, Wenting
    Jagadamma, Sindhu
    Kaiser, Klaus
    Kothawala, Dolly
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Mayes, Melanie A.
    Ciais, Philippe
    How much carbon can be added to soil by sorption?2021Inngår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 152, nr 2-3, s. 127-142Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantifying the upper limit of stable soil carbon storage is essential for guiding policies to increase soil carbon storage. One pool of carbon considered particularly stable across climate zones and soil types is formed when dissolved organic carbon sorbs to minerals. We quantified, for the first time, the potential of mineral soils to sorb additional dissolved organic carbon (DOC) for six soil orders. We compiled 402 laboratory sorption experiments to estimate the additional DOC sorption potential, that is the potential of excess DOC sorption in addition to the existing background level already sorbed in each soil sample. We estimated this potential using gridded climate and soil geochemical variables within a machine learning model. We find that mid- and low-latitude soils and subsoils have a greater capacity to store DOC by sorption compared to high-latitude soils and topsoils. The global additional DOC sorption potential for six soil orders is estimated to be 107 ± 13 Pg C to 1 m depth. If this potential was realized, it would represent a 7% increase in the existing total carbon stock.

    Fulltekst (pdf)
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  • 32.
    Abrate, Matteo
    et al.
    CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Bacciu, Clara
    CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Hast, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion. CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Marchetti, Andrea
    CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Minutoli, Salvatore
    CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Tesconi, Maurizio
    CNR Natl Res Council, Inst Informat & Telemat, I-56124 Pisa, Italy.
    Geomemories - A Platform for Visualizing Historical, Environmental and Geospatial Changes of the Italian Landscape2013Inngår i: ISPRS International Journal of Geo-Information. Special issue: Geospatial Monitoring and Modelling of Environmental Change, ISSN 2220-9964, Vol. 2, nr 2, s. 432-455Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The GeoMemories project aims at publishing on the Web and digitally preserving historical aerial photographs that are currently stored in physical form within the archives of the Aerofototeca Nazionale in Rome. We describe a system, available at http://www.geomemories.org, that lets users visualize the evolution of the Italian landscape throughout the last century. The Web portal allows comparison of recent satellite imagery with several layers of historical maps, obtained from the aerial photos through a complex workflow that merges them together. We present several case studies carried out in collaboration with geologists, historians and archaeologists, that illustrate the great potential of our system in different research fields. Experiments and advances in image processing technologies are envisaged as a key factor in solving the inherent issue of vast amounts of manual work, from georeferencing to mosaicking to analysis.

  • 33.
    Abrehdary, Majid
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Sjöberg, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Royal Inst Technol KTH, Div Geodesy & Satellite Positioning, SE-10044 Stockholm, Sweden.
    Remaining non-isostatic effects in isostatic-gravimetric Moho determination: is it needed?2023Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 234, nr 3, s. 2066-2074Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For long time the study of the Moho discontinuity (or Moho) has been a crucial topic in inferring the dynamics of the Earth's interior, and with profitable result it is mapped by seismic data, but due to the heterogeneous distribution of such data the quality varies over the world. Nevertheless, with the advent of satellite gravity missions, it is today possible to recover the Moho constituents (i.e. Moho depth; MD and Moho density contrast; MDC) via gravity observations based on isostatic models. Prior to using gravity observations for this application it must be stripped due to the gravitational contributions of known anomalous crustal density structures, mainly density variations of oceans, glacial ice sheets and sediment basins (i.e. stripping gravity corrections). In addition, the gravity signals related mainly with masses below the crust must also be removed. The main purpose of this study is to estimate the significance of removing also remaining non-isostatic effects (RNIEs) on gravity, that is, gravity effects that remain after the stripping corrections. This is carried out by using CRUST19 seismic crustal model and employing Vening Meinesz–Moritz (VMM) gravimetric-isostatic model in recovering the Moho constituents on a global scale to a resolution of 1° × 1°. To reach this goal, we present a new model, named MHUU22, formed by the SGGUGM2 gravitational field, Earth2014 topography, CRUST1.0 and CRUST19 seismic crustal models. Particularly, this study has its main emphasis on the RNIEs on gravity and Moho constituents to find out if we can modify the stripping gravity corrections by a specific correction of the RNIEs. The numerical results illustrate that the RMS differences between MHUU22 MD and the seismic model CRUST1.0 and least-squares combined model MOHV21 are reduced by 33 and 41 per cent by applying the NIEs, and the RMS differences between MHUU22 MDC and the seismic model CRUST1.0 and least-squares combined model MDC21 are reduced by 41 and 23 per cent when the above strategy for removing the RNIEs is applied. Hence, our study demonstrates that the specific correction for the RNIEs on gravity disturbance is significant, resulting in remarkable improvements in MHUU22, which more clearly visualize several crustal structures.

    Fulltekst (pdf)
    fulltext
  • 34.
    Abreu, Rafael
    et al.
    Westfalische Wilhelms Univ Munster, Inst Geophys, Corrensstr 24, D-48149 Munster, Germany.;Univ Granada, Inst Andaluz Geofis, Campus Cartuja S-N, E-18071 Granada, Spain..
    Kamm, Jochen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Westfalische Wilhelms Univ Munster, Inst Geophys, Corrensstr 24, D-48149 Munster, Germany.
    Reiss, Anne-Sophie
    Westfalische Wilhelms Univ Munster, Inst Geophys, Corrensstr 24, D-48149 Munster, Germany..
    Micropolar modelling of rotational waves in seismology2017Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 210, nr 2, s. 1021-1046Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this contribution we study elastic wave propagation via the introduction of the micropolar theory. As a generalization of a classical linear elastic medium, a micropolar medium allows each particle to have intrinsic rotational degrees of freedom (spin). We perform numerical experiments using the Pseudospectral method. We find analytical harmonic micropolar solutions for different problem configurations, which result in waveform differences between the classical linear elastic and micropolar media. In contrast to linear elastic media, wave propagation in micropolar media is dispersive. We study how the spin waveform depends on the micropolar elastic parameters and frequency content of the simulation. The micropolar effect on numerical seismograms has a direct implication on the phase, amplitude and arrival time. For frequencies lower than the cut-off frequency, the spin waveform has the same amplitude as the macrorotation field. For frequencies higher than the cut-off frequency, the amplitude of the spin waveform decreases with increasing frequency, so that then it is no longer comparable to the amplitude of macroscopic rotations. When both frequencies are equal there is no wave propagation. This work attempts to clarify the theory of micropolar media for its applications in seismology. We argue that micropolar theory should be further investigated for its potential uses in seismology to, for example, describe energy dissipation, seismograms recorded with rotational seismometers and rupture processes.

  • 35.
    Abril, Claudia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Seismicity and crustal structure in Iceland2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main goal of this Ph.D. thesis is to improve locations of earthquake hypocenters and to resolve heterogeneous crustal structure and its effects on travel times. The data and case studies are drawn from the Icelandic national SIL network and the temporary NICE project deploy-ment in the Tjörnes Fracture Zone. Iceland presents complex tectonics and active volcanism, consequences of its position astride the Mid-Atlantic Ridge between the European and North American plates and on top of a melting anomaly in the mantle below. Studies focused on characterizing the seismicity and the crustal structure are prerequisites for further seismologi-cal studies in Iceland, e.g., on seismic sources, the evolution of volcanic systems, activity on seismic faults and seismic hazard, among others.

    Different methods have been explored. First, we estimated empirically travel-time functions of seismic waves and their uncertainties for 65 stations in the Icelandic permanent network (SIL) using arrival times. The estimated travel-time functions and uncertainties were used to relocate the complete catalog applying a nested-search algorithm to this non-linear problem. The clearest changes in locations compared to the SIL solutions were obtained in the peripheral areas of the network, in particular in the Tjörnes Fracture Zone (North Iceland) and on the Reykjanes Peninsula (South Iceland).

    Relocations with empirical travel times were used complementary with constrained earth-quake relocation and the collapsing methods of Li et al. [2016] to study the seismicity in the Hengill area (South Iceland). Patterns in the seismicity in the final locations reproduce lin-eations previously found in relative relocations in the area. The brittle-ductile transition was estimated, obtaining a smaller depth in the northern part of the region, dominated by volcanic processes, compared with the south, controlled by tectonic processes. Furthermore, the Hengill fissure swarm that hosts two large geothermal power plants, was found to have deeper penetrat-ing earthquakes than adjacent volcanic areas, presumably because it is more effectively cooled.

    Local earthquake tomography was used to solve simultaneously for earthquake location and velocity structure in the Tjörnes Fracture Zone, using data from the temporary network installed during the North ICeland Experiment, and data from the permanent SIL network. 3-D velocity models for P- and S-waves were obtained for the area and used to relocate the complete SIL catalog. The results demonstrate significant structures associated with the different branches of this complex transform region, e.g. low velocities along the Husavík-Flatey Fault (HFF), penetrating to about 10 km depth. Low Vp/Vs ratios were also mapped at depth along the HFF indicating presence of highly compressible fluids in the middle crust. In general, the seismicity pattern was shifted towards the surface from SIL locations and clarified in its lateral distribution. This highlighted a zone of concentrated deformation in the Tjörnes Microplate, which intersections with the two main strands of the overall zone coincide with changes in their geometry and character.

    Delarbeid
    1. Relocating earthquakes with empirical traveltimes
    Åpne denne publikasjonen i ny fane eller vindu >>Relocating earthquakes with empirical traveltimes
    2018 (engelsk)Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 214, nr 3, s. 2098-2114Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A strategy is proposed to incorporate effects of 3-D velocity variations on earthquake locationsusing empirical traveltimes (ETTs). Traveltime residuals are interpolated from those predictedusing a 1-D velocity reference, mapped on to the hypocentres of corresponding earthquakesfor each station in a network. First, station corrections are computed by averaging the residualsover a fixed scale. Then, summary-ray variograms are used to estimate uncertainty and that,in turn, is used to tune a local fit to neighbouring residuals to refine the corrections. Resulting3-D traveltime estimates are then used as a description of the forward problem in a nonlineargrid-search relocation. Data are weighted according to the estimated uncertainty. Data fromthe Icelandic Southern Iceland Lowlands (SIL) national seismic network are used to test thestrategy. ETTs are estimated forP- andS-waves at 65 stations in the SIL network, basedon four million arrival time readings of 300.000 events registered between 1990 and 2012.ETTs are strongly correlated for the two wave types. The spatial variations of the predictedcorrections are consistently comparable or somewhat less forS-waves thanP-waves. Thisfeature suggests variations of theVP/VSratio in the Icelandic crust. Error estimates are alsostrongly correlated for the two wave types and between nearby stations. Relocations aretested by comparison with explosions and small populations of well-located events withindenser subnetworks. Relocations result in modestly enhanced clustering of explosions andearthquakes and significantly improved depth estimates. Estimates of the random relocationerror are statistically better behaved than those of the SIL system. They are in general reduced,as is expected since 3-D heterogeneity is now partly taken into account.

    sted, utgiver, år, opplag, sider
    Oxford University Press, 2018
    Emneord
    Body waves, earthquake monitoring
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-363251 (URN)10.1093/gji/ggy246 (DOI)000439648000037 ()
    Forskningsfinansiär
    EU, FP7, Seventh Framework Programme, 308377
    Tilgjengelig fra: 2018-10-15 Laget: 2018-10-15 Sist oppdatert: 2018-12-05bibliografisk kontrollert
    2. Seismicity of the Hengill area, SW Iceland: Details revealed by catalog relocation and collapsing
    Åpne denne publikasjonen i ny fane eller vindu >>Seismicity of the Hengill area, SW Iceland: Details revealed by catalog relocation and collapsing
    2019 (engelsk)Inngår i: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 376, s. 15-26Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The spatial distribution of seismicity in the Hengill region, SW Iceland, is analyzed by relocation and collapsing. The Hengill region is a diffuse triple junction with volcano-tectonic activity associated with rifting, tectonic activity on a transecting transform and induced seismicity due to drilling and injection of fluid into geothermal fields. The Icelandic Meteorological Office has compiled 114,000 events over a 20-year period within an area of approximately 600 km2. The events in their catalog are relocated by application of empirical travel-time tables using a non-linear location strategy. The relocations are then redone applying a Bayesian inversion using the catalog event density as a prior. Finally, they are collapsed using the same catalog density as an attractor. We show that this catalog processing reproduces details of the spatial pattern of seismicity that independently emerges from relative relocations of a small subset of the catalog events (swarm activity). In particular, the predominant faulting orientations are reproduced in different parts of the region and the depth distribution of events resembles that obtained by dense deployments in the area. Its depth extent varies between 5 and 7 km in the northern part of the region, where volcanic processes dominate, and between 7 and 8 km in the southern part, where tectonic deformation is predominant. Induced seismicity is shallower than adjacent natural seismicity. An intriguing lineation emerges in the lateral distribution of inferred depth to the brittle-ductile transition in the northern volcanic part of the region, which is parallel to the strike of the fissure swarms in the area. Associating this transition with an isotherm (650 °C), the Hengill volcanic system and its fissure swarm appear to be considerably cooler than the Hrómundartindur system. This may relate to a recent intrusion into the latter or more efficient cooling in the Hengill fissure swarm due to deeper penetrating permeability. In both cases this has potential consequences for geothermal exploitation in the area.

    Emneord
    Seismicity, Hengill, Relocation, Brittle-ductile transition, Earthquake catalog, Iceland
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-327037 (URN)10.1016/j.jvolgeores.2019.03.008 (DOI)000466257600002 ()
    Tilgjengelig fra: 2017-07-31 Laget: 2017-07-31 Sist oppdatert: 2020-05-12bibliografisk kontrollert
    3. Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)
    Åpne denne publikasjonen i ny fane eller vindu >>Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)
    2021 (engelsk)Inngår i: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 126, nr 6, artikkel-id e2020JB020212Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Local earthquake tomography has been carried out in the Tjornes Fracture Zone. This transform region connects the Mid-Atlantic Ridge to the Northern Volcanic Zone in Iceland in a mostly offshore area. The challenge to record seismic information in this area was the motivation for the North ICeland Experiment (NICE). Fourteen ocean-bottom seismometers and eleven on-land stations were installed in the project and operated simultaneously with the permanent Icelandic seismic network (SIL) during summer 2004. Data from the experiment were used to estimate P- and S-wave crustal velocities. Also, the gravity anomaly was derived for comparison with the tomographic results. Upper-crustal velocities are found to be relatively low in the offshore region. In particular, low velocities are mapped along the Husavik-Flatey Fault, where a more confined negative gravity anomaly and a sedimentary basin are found. Low velocities are also mapped along the Grimsey Oblique Rift and in a zone connecting these two main lineaments. The northern half of the aseismic Grimsey Shoal appears as a fast anomaly. Furthermore, localized high-velocity anomalies are found beneath northern Trollaskagi and Flateyjarskagi Peninsulas, where bedrock dates from Upper and Middle Miocene (10-15 Ma). Regions of low Vp/Vs ratios are mapped at depth along the main lineaments. Low velocities along the lineaments are interpreted as due to fracturing extending into the middle crust, while high velocities in the upper crust beneath Tertiary formations are associated with relic volcanoes. Low Vp/Vs variations along the lineaments are interpreted as due to the presence of supercritical fluids.

    sted, utgiver, år, opplag, sider
    American Geophysical Union (AGU), 2021
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-363252 (URN)10.1029/2020JB020212 (DOI)000665206200017 ()
    Forskningsfinansiär
    Swedish Research Council, 2003-3600German Research Foundation (DFG), Da478/13-1German Research Foundation (DFG), RI1220/2-1
    Merknad

    Title in dissertation list of papers: Local earthquake tomography and earthquake relocation in the Tjörnes Fracture Zone (North Iceland)

    Tilgjengelig fra: 2018-10-15 Laget: 2018-10-15 Sist oppdatert: 2024-01-15bibliografisk kontrollert
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    presentationsbild
  • 36.
    Abril, Claudia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Gudmundsson, Ólafur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Relocating earthquakes with empirical traveltimes2018Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 214, nr 3, s. 2098-2114Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A strategy is proposed to incorporate effects of 3-D velocity variations on earthquake locationsusing empirical traveltimes (ETTs). Traveltime residuals are interpolated from those predictedusing a 1-D velocity reference, mapped on to the hypocentres of corresponding earthquakesfor each station in a network. First, station corrections are computed by averaging the residualsover a fixed scale. Then, summary-ray variograms are used to estimate uncertainty and that,in turn, is used to tune a local fit to neighbouring residuals to refine the corrections. Resulting3-D traveltime estimates are then used as a description of the forward problem in a nonlineargrid-search relocation. Data are weighted according to the estimated uncertainty. Data fromthe Icelandic Southern Iceland Lowlands (SIL) national seismic network are used to test thestrategy. ETTs are estimated forP- andS-waves at 65 stations in the SIL network, basedon four million arrival time readings of 300.000 events registered between 1990 and 2012.ETTs are strongly correlated for the two wave types. The spatial variations of the predictedcorrections are consistently comparable or somewhat less forS-waves thanP-waves. Thisfeature suggests variations of theVP/VSratio in the Icelandic crust. Error estimates are alsostrongly correlated for the two wave types and between nearby stations. Relocations aretested by comparison with explosions and small populations of well-located events withindenser subnetworks. Relocations result in modestly enhanced clustering of explosions andearthquakes and significantly improved depth estimates. Estimates of the random relocationerror are statistically better behaved than those of the SIL system. They are in general reduced,as is expected since 3-D heterogeneity is now partly taken into account.

  • 37.
    Abril, Claudia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Mai, Martin
    King Abdullah University of Science and Technology.
    Jonsson, Sigurjon
    King Abdullah University of Science and Technology.
    Ground-motion simulations around the Husavik-Flatey Fault, North IcelandManuskript (preprint) (Annet vitenskapelig)
  • 38.
    Abril, Claudia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Icelandic Meteorol Off IMO, Reykjavik, Iceland..
    Tryggvason, Ari
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Gudmundsson, Ólafur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Steffen, Rebekka
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Lantmäteriet, Gävle, Sweden..
    Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)2021Inngår i: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 126, nr 6, artikkel-id e2020JB020212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local earthquake tomography has been carried out in the Tjornes Fracture Zone. This transform region connects the Mid-Atlantic Ridge to the Northern Volcanic Zone in Iceland in a mostly offshore area. The challenge to record seismic information in this area was the motivation for the North ICeland Experiment (NICE). Fourteen ocean-bottom seismometers and eleven on-land stations were installed in the project and operated simultaneously with the permanent Icelandic seismic network (SIL) during summer 2004. Data from the experiment were used to estimate P- and S-wave crustal velocities. Also, the gravity anomaly was derived for comparison with the tomographic results. Upper-crustal velocities are found to be relatively low in the offshore region. In particular, low velocities are mapped along the Husavik-Flatey Fault, where a more confined negative gravity anomaly and a sedimentary basin are found. Low velocities are also mapped along the Grimsey Oblique Rift and in a zone connecting these two main lineaments. The northern half of the aseismic Grimsey Shoal appears as a fast anomaly. Furthermore, localized high-velocity anomalies are found beneath northern Trollaskagi and Flateyjarskagi Peninsulas, where bedrock dates from Upper and Middle Miocene (10-15 Ma). Regions of low Vp/Vs ratios are mapped at depth along the main lineaments. Low velocities along the lineaments are interpreted as due to fracturing extending into the middle crust, while high velocities in the upper crust beneath Tertiary formations are associated with relic volcanoes. Low Vp/Vs variations along the lineaments are interpreted as due to the presence of supercritical fluids.

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    fulltext
  • 39.
    Abtahi, Sayyed Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Airborne Gravity Gradient, Magnetic and VLF datasets: Case studies of modelling, inversion and interpretation2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Northern Sweden is one of the largest hosts for mineral resources in Europe and always has been an interesting area for researchers from various disciplines of Earth sciences. This dissertation is a comprehensive summary of three case study papers on airborne VLF, gravity gradient and magnetic data in the area.

    In the first paper, tensor VLF data is extracted from an old data set which contains only the total and the vertical magnetic components. The anomalous part of the horizontal magnetic field components is computed by a Hilbert transform of the vertical magnetic field. The normal part of the horizontal magnetic field component is computed as a function of total, vertical and anomalous part of horizontal magnetic fields. The electric field is also calculated for TE mode and impedance tensor and apparent resistivity are computed. In addition tippers are calculated for two transmitters and inverted by a 3D inversion algorithm. Comparison of the estimated model and geology map of bedrock shows that lower resistivity zones are correlated with mineralizations.

    The second paper deals with the internal consistency of airborne gravity gradient data. The six components of the data are estimated from a common potential function. It is shown that the data is adequately consistent but at shorter land clearances the difference between the estimated data and the original data is larger. The technique is also used for computing the Bouguer anomaly from terrain corrected FTG data. Finally the data is inverted in 3D, which shows that the estimated density model in shallow depth is dominated by short wave length features.

    Inversion of TMI data is the topic of the third paper where a new type of reference model for 3D inversion of magnetic data is proposed by vertically extending the estimated magnetization of a 2D terrain magnetization model. The final estimated 3D result is compared with the magnetization model where no reference model is used. The comparison shows that using the reference model helps the high magnetization zones in the estimated model at shallow depths to be better correlated with measured high remanent magnetization from rock samples. The high magnetization zones are also correlated with gabbros and volcanic metasediments.

    Delarbeid
    1. Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden
    2016 (engelsk)Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 81, nr 5, s. B135-B147Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In 1985, the mining company Luossavaara-Kiirunavaara Aktiebolag collected airborne very-low-frequency (VLF) data in northern Sweden. The operators stored only the vertical component and the total magnetic field, which at that time were believed to be sufficient for qualitative interpretation. Therefore, the data could not be directly used for quantitative tensor VLF processing and inversion. To avoid the costs of resurveying, we have developed a novel technique to estimate the tippers from the measured VLF data by computing anomalous and normal parts of the horizontal components of the magnetic field from two transmitters separately. Retrieval of the normal horizontal components was possible because one component of the horizontal magnetic field was used as the phase reference during the measurements. Additionally, we have determined how the approximate apparent resistivity suitable for data visualization can be computed from the components of the magnetic field assuming an average normal resistivity of the subsurface. Maps of apparent resistivity combined with topography show a clear correlation between high topography and high resistivity, whereas conductive zones are found in valleys in between. More importantly, the 3D model inverted from the calculated tippers shows excellent agreement with a map of the surface geology. Based on this comparison, some less resistive zones can be related to fluids in fractures and others can be related to mineralized contact zones. We suggest to focus further exploration on conductive zones surrounding areas with basaltic composition.

    Emneord
    case history, inversion, interpretation, electromagnetics
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-300086 (URN)10.1190/GEO2015-0296.1 (DOI)000392752200002 ()
    Tilgjengelig fra: 2016-08-02 Laget: 2016-08-02 Sist oppdatert: 2018-10-29
    2. Consistency investigation, vertical gravity estimation and inversion of airborne gravity gradient data – A case study from northern Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>Consistency investigation, vertical gravity estimation and inversion of airborne gravity gradient data – A case study from northern Sweden
    2016 (engelsk)Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 81, nr 3, s. B65-B76Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    For airborne gravity gradient data, it is a challenge to distinguish between high-frequency intrinsic and dynamically produced noise caused by the aircraft and small-scale effects from shallow density variations. To facilitate consistent interpretation, techniques that include all of the measured gravity gradient components are particularly promising. We represented the measurements by a common potential function accounting for lateral and height variations. Thus, it was possible to evaluate the internal consistency between the measured components and to identify components with bias or particularly strong noise. As an extra benefit for data sets that contain terrain-corrected and nonterrain-corrected gravity gradient measurements at flight altitude, we estimated terrain-corrected anomalies on the topographic relief using downward continuation and retrieved nonterrain-corrected gravity gradient data suitable for inversion using upward continuation. For a field data set from northern Sweden, the largest differences (up to 50 eotvos) between the measured and estimated components of the gravity gradient data were found in areas of high topographical relief. But the average residual standard deviations of the individual components were between 3.6 and 7.4 eotvos, indicating that the components were consistent in an average sense. We have determined the successful conversion of terrain-corrected airborne gravity gradient data to Bouguer gravity data on the topographic relief using ground-based vertical gravity data as a reference. A 3D inverse model computed from the nonterrain-corrected data clearly showed the depth extent of the geologic structures observed at the surface, but it only produced a weak representation of the shallow structure. In contrast, a 2D surface density model in which only lateral variations of density in the topographic relief was allowed exhibited more realistic density distributions in fair correlation with geology.

    Emneord
    gravity, modeling, noise, processing
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-300024 (URN)10.1190/geo2014-0428.1 (DOI)000384984900008 ()
    Tilgjengelig fra: 2016-08-02 Laget: 2016-08-02 Sist oppdatert: 2017-11-28bibliografisk kontrollert
    3. A new reference model for 3D inversion of airborne magnetic data in hilly terrain – a case study from northern Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>A new reference model for 3D inversion of airborne magnetic data in hilly terrain – a case study from northern Sweden
    (engelsk)Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-300111 (URN)
    Tilgjengelig fra: 2016-08-02 Laget: 2016-08-02 Sist oppdatert: 2016-09-05
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  • 40.
    Abtahi, Sayyed Mohammad
    et al.
    Isfahan Univ Technol, Dept Min Engn, Esfahan, Iran.
    Pedersen, Laust Börsting
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Kamm, Jochen
    Univ Munster, Dept Geophys, Munster, Germany.
    Kalscheuer, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    A new reference model for 3D inversion of airborne magnetic data in hilly terrain: A case study from northern Sweden2018Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 83, nr 1, s. B1-B12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The inherent nonuniqueness in modeling magnetic data can be partly reduced by adding prior information, either as mathematical constructs or simply as bounds on magnetization obtained from laboratory measurements. If a good prior model can be used as a reference model, then the quality of estimated models through an inverse approach can be greatly improved. But even though data on magnetic properties of rocks might exist, their distribution may often be quite irregular on local and regional scales, so that it is difficult to define representative classes of rock types suitable for constraining geophysical models of magnetization. We have developed a new way of constructing a reference model that varies only laterally and is confined to the part of the terrain that lies above the lowest topography in the area. To obtain this model, several estimated 2D magnetization distributions were constructed by data inversion as a function of the iteration number. Then, a suitable 2D model of the magnetization in the topography was chosen as a starting point for constructing a 3D reference model by modifying it with a vertical decay such that its average source depth was the same for all horizontal positions. The average source depth of the reference model was chosen to satisfy the average source depth obtained from analyzing the radial power spectrum of the area studied. Finally, the measured magnetic data were inverted in three dimensions using the given reference model. For a selected reference model, shallow structures indicated a better overall correlation with large remanent magnetizations measured on rock samples from the area. Throughout the entire model, the direction of magnetization was allowed to vary freely. We found that the Euclidean norm of the estimated model was reduced compared with the case where the magnetization direction was fixed.

  • 41.
    Abtahi, Sayyed Mohammad
    et al.
    Uppsala University.
    Pedersen, Laust
    Kamm, Jochen
    Kalscheuer, Thomas
    A new reference model for 3D inversion of airborne magnetic data in hilly terrain – a case study from northern SwedenArtikkel i tidsskrift (Fagfellevurdert)
  • 42.
    Abtahi, Sayyed Mohammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Isfahan Univ Technol, Dept Min Engn, Esfahan, Iran.
    Pedersen, Laust
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Kamm, Jochen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Kalscheuer, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Consistency investigation, vertical gravity estimation and inversion of airborne gravity gradient data – A case study from northern Sweden2016Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 81, nr 3, s. B65-B76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For airborne gravity gradient data, it is a challenge to distinguish between high-frequency intrinsic and dynamically produced noise caused by the aircraft and small-scale effects from shallow density variations. To facilitate consistent interpretation, techniques that include all of the measured gravity gradient components are particularly promising. We represented the measurements by a common potential function accounting for lateral and height variations. Thus, it was possible to evaluate the internal consistency between the measured components and to identify components with bias or particularly strong noise. As an extra benefit for data sets that contain terrain-corrected and nonterrain-corrected gravity gradient measurements at flight altitude, we estimated terrain-corrected anomalies on the topographic relief using downward continuation and retrieved nonterrain-corrected gravity gradient data suitable for inversion using upward continuation. For a field data set from northern Sweden, the largest differences (up to 50 eotvos) between the measured and estimated components of the gravity gradient data were found in areas of high topographical relief. But the average residual standard deviations of the individual components were between 3.6 and 7.4 eotvos, indicating that the components were consistent in an average sense. We have determined the successful conversion of terrain-corrected airborne gravity gradient data to Bouguer gravity data on the topographic relief using ground-based vertical gravity data as a reference. A 3D inverse model computed from the nonterrain-corrected data clearly showed the depth extent of the geologic structures observed at the surface, but it only produced a weak representation of the shallow structure. In contrast, a 2D surface density model in which only lateral variations of density in the topographic relief was allowed exhibited more realistic density distributions in fair correlation with geology.

  • 43.
    Abtahi, Sayyed Mohammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Isfahan Univ Technol, Dept Min Engn, Esfahan, Iran.
    Pedersen, Laust
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Kamm, Jochen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik. Univ Munster, Dept Geophys, Munster, Germany.
    Kalscheuer, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden2016Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 81, nr 5, s. B135-B147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In 1985, the mining company Luossavaara-Kiirunavaara Aktiebolag collected airborne very-low-frequency (VLF) data in northern Sweden. The operators stored only the vertical component and the total magnetic field, which at that time were believed to be sufficient for qualitative interpretation. Therefore, the data could not be directly used for quantitative tensor VLF processing and inversion. To avoid the costs of resurveying, we have developed a novel technique to estimate the tippers from the measured VLF data by computing anomalous and normal parts of the horizontal components of the magnetic field from two transmitters separately. Retrieval of the normal horizontal components was possible because one component of the horizontal magnetic field was used as the phase reference during the measurements. Additionally, we have determined how the approximate apparent resistivity suitable for data visualization can be computed from the components of the magnetic field assuming an average normal resistivity of the subsurface. Maps of apparent resistivity combined with topography show a clear correlation between high topography and high resistivity, whereas conductive zones are found in valleys in between. More importantly, the 3D model inverted from the calculated tippers shows excellent agreement with a map of the surface geology. Based on this comparison, some less resistive zones can be related to fluids in fractures and others can be related to mineralized contact zones. We suggest to focus further exploration on conductive zones surrounding areas with basaltic composition.

  • 44.
    Abyaneh, Morteza Y
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Filosofiska institutionen, Avdelningen för teoretisk filosofi.
    Electrocrystallization: Modelling and Its Applications2014Inngår i: Development in Electrochemistry: Science Inspired by Martin Fleischmann / [ed] Derek Pletcher, Zhong-Qun Tian and David E. Williams, John Wiley & Sons, 2014, 1, s. 49-64Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Mathematical modeling of the electrocrystallization processes and its applications has long been a subject dear to Martin Fleischmann. The study of nucleation is fundamental to the understanding of crystallization. In the context of electrocrystallization, the terms can be applied to phase formation at preferred sites on the electrode surface and phase formation at surfaces without such sites. Two models of nucleation are presented: a heterogeneous model (nucleation on an indent); and a spherical-cap model representing homogeneous nucleation. The transients are recorded by applying a two-step potential profile to the working electrode. This procedure ensures the reduction of the initial falling background/charging current, so that the magnitude of this initial current cannot mask the very early stages of electrocrystallization. Martin sought to establish an approach to nucleation based on quantum electrodynamics.

  • 45.
    Acikkol, Naz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Testing the Cretaceous Diversity of Ichthyosaurs and Their Extinction Hypotheses Using a Quantitative Approach2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As portrayed in Before the Dinosaur: the Historical Significance of the Fossil Marine Reptiles, ichthyosaurs, as other Mesozoic marine amniotes, have been unfairly overshadowed by dinosaurs in both popular culture and the field of vertebrate palaeontology. Yet by the effort of dedicated researchers, work on these fish-like marine reptiles had never died out, and in fact a second wave of interest emerged in the late 20th century. Since then, research on ichthyosaurs has focused on discovery of new taxa, assessments of their palaeobiology, and quantitative analyses of their diversity. Despite ever-growing interests, patterns and mechanisms leading up to their extinction in the Cenomanian were insufficiently evaluated. In other words, hypotheses focusing on abrupt extinction linked to a crash in prey diversity, notably belemnites, over a catastrophic event at the end-Cenomanian remain poorly tested. The current project thus aims to test: 1) whether the Cretaceous diversity of ichthyosaurs reflects biological signals, and 2) correlation of their diversity with the diversity of Mesozoic cephalopods, such as belemnites and ammonites. In this regard, a species-level dataset of Cretaceous belemnites including belemnite-bearing formations was built to be employed together with the occurrence-based ichthyosaur and ammonite datasets in the same taxic level. Raw taxic counts, as observed diversities of the clades, were quantified in two different temporal scales, and compared with two sampling proxies. The model-based method was then applied to correct all taxic counts based on the two proxies in both time bins to acquire expected diversities of all the clades. Comparisons resulted in strong correlations between the clades’ observed diversities and proxies exposing biased patterns under the influence of sampling intensity. Whereas both observed and expected diversities show no evidence of a causal relationship between the predator and prey groups, suggesting that the latter’s diversity seems not being a parameter for the former’s, and thus being unsupportive for a prey-driven demise of the predator. Furthermore, the expected trend of ichthyosaurs indicates lower Albian diversity gradually declining towards their extinction in the Cenomanian, which appears to be contrasting with recent studies.

    Fulltekst (pdf)
    DegreeProject_313
  • 46.
    Adamaki, Angeliki
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Seismicity Analyses Using Dense Network Data: Catalogue Statistics and Possible Foreshocks Investigated Using Empirical and Synthetic Data2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Precursors related to seismicity patterns are probably the most promising phenomena for short-term earthquake forecasting, although it remains unclear if such forecasting is possible. Foreshock activity has often been recorded but its possible use as indicator of coming larger events is still debated due to the limited number of unambiguously observed foreshocks. Seismicity data which is inadequate in volume or character might be one of the reasons foreshocks cannot easily be identified. One method used to investigate the possible presence of generic seismicity behavior preceding larger events is the aggregation of seismicity series. Sequences preceding mainshocks chosen from empirical data are superimposed, revealing an increasing average seismicity rate prior to the mainshocks. Such an increase could result from the tendency of seismicity to cluster in space and time, thus the observed patterns could be of limited predictive value. Randomized tests using the empirical catalogues imply that the observed increasing rate is statistically significant compared to an increase due to simple clustering, indicating the existence of genuine foreshocks, somehow mechanically related to their mainshocks. If network sensitivity increases, the identification of foreshocks as such may improve. The possibility of improved identification of foreshock sequences is tested using synthetic data, produced with specific assumptions about the earthquake process. Complications related to background activity and aftershock production are investigated numerically, in generalized cases and in data-based scenarios. Catalogues including smaller, and thereby more, earthquakes can probably contribute to better understanding the earthquake processes and to the future of earthquake forecasting. An important aspect in such seismicity studies is the correct estimation of the empirical catalogue properties, including the magnitude of completeness (Mc) and the b-value. The potential influence of errors in the reported magnitudes in an earthquake catalogue on the estimation of Mc and b-value is investigated using synthetic magnitude catalogues, contaminated with Gaussian error. The effectiveness of different algorithms for Mc and b-value estimation are discussed. The sample size and the error level seem to affect the estimation of b-value, with implications for the reliability of the assessment of the future rate of large events and thus of seismic hazard.

    Delarbeid
    1. EVIDENCE OF PRECURSORY PATTERNS IN AGGREGATED TIME SERIES
    Åpne denne publikasjonen i ny fane eller vindu >>EVIDENCE OF PRECURSORY PATTERNS IN AGGREGATED TIME SERIES
    2016 (engelsk)Inngår i: Bulletin of the Geological Society of Greece, vol. L, 2016, Proceedings of the 14th Intern. Congress, Thessaloniki, May 2016, 2016, Vol. 50Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We investigate temporal changes in seismic activity observed in the West Corinth Gulfand North-West Peloponnese during 2008 to 2010. Two major earthquake sequencestook place in the area at that time (in 2008 and 2010). Our aim is to analyse Greekseismicity to attempt to confirm the existence or non-existence of seismic precursorsprior to the strongest earthquakes. Perhaps because the area is geologically andtectonically complex, we found that it was not possible to fit the data well using aconsistent Epidemic Type Aftershock Sequence (ETAS) model. Nor could weunambiguously identify foreshocks to individual mainshocks. Therefore we soughtpatterns in aggregated foreshock catalogues. We set a magnitude threshold (M3.5)above which all the earthquakes detected in the study area are considered as“mainshocks”, and we combined all data preceding these into a single foreshockcatalogue. This reveals an increase in seismicity rate not robustly observable forindividual cases. The observed effect is significantly greater than that consistent withstochastic models, including ETAS, thus indicating genuine foreshock activity withpotential useful precursory power, if sufficient data is available, i.e. if the magnitudeof completeness is sufficiently low.

    Abstract [el]

    Μελετάμε χρονικές μεταβολές της σεισμικής δραστηριότητας στο Δυτικό ΚορινθιακόΚόλπο και τη Βορειοδυτική Πελοπόννησο κατά τα έτη 2008-2010. Δύο σημαντικέςσεισμικές ακολουθίες σημειώθηκαν στην περιοχή σε αυτή την περίοδο (2008 και 2010).Στόχος είναι να αναλύσουμε τη σεισμικότητα ώστε να επιβεβαιώσουμε την ύπαρξη ή μηπροσεισμικής δραστηριότητας πριν από τους μεγαλύτερους σεισμούς. Λόγω τηςγεωλογικής και τεκτονικής πολυπλοκότητας της περιοχής, δεν ήταν εφικτή η εφαρμογήενός ενιαίου μοντέλου Επιδημικού Τύπου Μετασεισμικών Ακολουθιών (ETAS), ούτε ηαναγνώριση προσεισμών μεμονωμένων κυρίων σεισμών. Επομένως, αναζητήσαμεανάλογα μοτίβα σε ενιαίους καταλόγους προσεισμών. Θέσαμε ένα μέγεθος (Μ3.5)πάνω από το οποίο όλοι οι σεισμοί θεωρούνται “κύριοι”, και συνδυάσαμε τα δεδομέναπου προηγούνται αυτών, σε ένα κοινό κατάλογο. Αναδεικνύεται έτσι μια αύξηση τουρυθμού σεισμικότητας που δεν είναι εμφανής σε μεμονωμένες περιπτώσεις και είναι πιοσημαντική από εκείνη που προβλέπεται από στοχαστικά μοντέλα, όπως το ETAS,υποδηλώνοντας την ύπαρξη προσεισμών που μπορούν να δώσουν τη δυνατότηταπρόγνωσης αν υπάρχει ικανοποιητικό πλήθος δεδομένων, δηλ. αν το μέγεθοςπληρότητας είναι αρκετά χαμηλό.

    Emneord
    Corinth Gulf, Seismicity, Aggregated Foreshock Catalogues, Κορινθιακός Κόλπος, Σεισμικότητα, Ενιαίοι Κατάλογοι Προσεισμών
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-295440 (URN)
    Konferanse
    14th International Congress, Geological Society of Greece, Thessaloniki, May 2016
    Tilgjengelig fra: 2016-06-07 Laget: 2016-06-07 Sist oppdatert: 2017-08-21bibliografisk kontrollert
    2. Precursory Activity Before Larger Events in Greece Revealed by Aggregated Seismicity Data
    Åpne denne publikasjonen i ny fane eller vindu >>Precursory Activity Before Larger Events in Greece Revealed by Aggregated Seismicity Data
    2017 (engelsk)Inngår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 174, nr 3, s. 1331-1343Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We investigate the seismicity rate behaviour in and around Greece during 2009, seeking significant changes in rate preceding larger events. For individual larger events it is difficult to clearly distinguish precursory rate changes from other, possibly unrelated, variations in seismicity. However, when we aggregate seismicity data occurring within a radius of 10 km and in a 50-day window prior to earthquakes with, e. g. magnitude C3.5, the resulting aggregated time series show a clearly increasing trend starting 2-3 weeks prior to the "mainshock'' time. We apply statistical tests to investigate if the observed behaviour may be simply consistent with random (poissonian) variations, or, as some earlier studies suggest, with clustering in the sense that high activity rates at some time may imply increased rates later, and thus (randomly) greater probability of larger coming events than for periods of lower seismicity. In this case, rate increases have little useful predictive power. Using data from the entire catalogue, the aggregated rate changes before larger events are clearly and strongly statistically significant and cannot be explained by such clustering. To test this we choose events at random from the catalogue as potential "mainshocks''. The events preceding the randomly chosen earthquakes show less pronounced rate increases compared to the observed rate changes prior to larger events. Similar behaviour is observed in data sub-sets. However, statistical confidence decreases for geographical subsets containing few "mainshocks'' as it does when data are weighted such that "mainshocks'' with many preceding events are strongly downweighted relative to those with fewer. The analyses suggest that genuine changes in aggregated rate do occur prior to larger events and that this behaviour is not due to a small number of mainshocks with many preceding events dominating the analysis. It does not automatically follow that it will be possible to routinely observe precursory changes prior to individual larger events, but there is a possibility that this may be feasible, e. g. with better data from more sensitive networks.

    sted, utgiver, år, opplag, sider
    SPRINGER BASEL AG, 2017
    Emneord
    Temporal seismicity patterns, aggregated data, precursory activity, Greece
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-320921 (URN)10.1007/s00024-017-1465-6 (DOI)000396834700039 ()
    Tilgjengelig fra: 2017-04-27 Laget: 2017-04-27 Sist oppdatert: 2017-08-21bibliografisk kontrollert
    3. Advantages and Limitations of Foreshock Activity as a Useful Tool for Earthquake Forecasting
    Åpne denne publikasjonen i ny fane eller vindu >>Advantages and Limitations of Foreshock Activity as a Useful Tool for Earthquake Forecasting
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Emneord
    Accelerating Seismicity, Earthquake Predictability
    HSV kategori
    Forskningsprogram
    Geofysik med inriktning mot seismologi
    Identifikatorer
    urn:nbn:se:uu:diva-328055 (URN)
    Tilgjengelig fra: 2017-08-16 Laget: 2017-08-16 Sist oppdatert: 2017-08-21
    4. Impact of Magnitude Uncertainties on Seismic Catalogue Properties
    Åpne denne publikasjonen i ny fane eller vindu >>Impact of Magnitude Uncertainties on Seismic Catalogue Properties
    Vise andre…
    2018 (engelsk)Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 213, nr 2, s. 940-951Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Catalogue-based studies are of central importance in seismological research, to investigate the temporal, spatial and size distribution of earthquakes in specified study areas. Methods for estimating the fundamental catalogue parameters like the Gutenberg–Richter (G-R) b-value and the completeness magnitude (Mc) are well established and routinely applied. However, the magnitudes reported in seismicity catalogues contain measurement uncertainties which may significantly distort the estimation of the derived parameters. In this study, we use numerical simulations of synthetic data sets to assess the reliability of different methods for determining b-value and Mc, assuming the G-R law validity. After contaminating the synthetic catalogues with Gaussian noise (with selected standard deviations), the analysis is performed for numerous data sets of different sample size (N). The noise introduced to the data generally leads to a systematic overestimation of magnitudes close to and above Mc. This fact causes an increase of the average number of events above Mc, which in turn leads to an apparent decrease of the b-value. This may result to a significant overestimation of seismicity rate even well above the actual completeness level. The b-value can in general be reliably estimated even for relatively small data sets (N < 1000) when only magnitudes higher than the actual completeness level are used. Nevertheless, a correction of the total number of events belonging in each magnitude class (i.e. 0.1 unit) should be considered, to deal with the magnitude uncertainty effect. Because magnitude uncertainties (here with the form of Gaussian noise) are inevitable in all instrumental catalogues, this finding is fundamental for seismicity rate and seismic hazard assessment analyses. Also important is that for some data analyses significant bias cannot necessarily be avoided by choosing a high Mc value for analysis. In such cases, there may be a risk of severe miscalculation of seismicity rate regardless the selected magnitude threshold, unless possible bias is properly assessed.

    Emneord
    Statistical Seismology, Earthquake Catalogue Properties, Completeness Magnitude, b-value
    HSV kategori
    Forskningsprogram
    Statistik; Geofysik med inriktning mot seismologi
    Identifikatorer
    urn:nbn:se:uu:diva-328053 (URN)10.1093/gji/ggy023 (DOI)000448720300016 ()
    Tilgjengelig fra: 2017-08-16 Laget: 2017-08-16 Sist oppdatert: 2019-01-22bibliografisk kontrollert
    Fulltekst (pdf)
    fulltext
    Download (jpg)
    preview image
  • 47.
    Adamaki, Angeliki K.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Roberts, Roland G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Precursory Activity Before Larger Events in Greece Revealed by Aggregated Seismicity Data2017Inngår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 174, nr 3, s. 1331-1343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the seismicity rate behaviour in and around Greece during 2009, seeking significant changes in rate preceding larger events. For individual larger events it is difficult to clearly distinguish precursory rate changes from other, possibly unrelated, variations in seismicity. However, when we aggregate seismicity data occurring within a radius of 10 km and in a 50-day window prior to earthquakes with, e. g. magnitude C3.5, the resulting aggregated time series show a clearly increasing trend starting 2-3 weeks prior to the "mainshock'' time. We apply statistical tests to investigate if the observed behaviour may be simply consistent with random (poissonian) variations, or, as some earlier studies suggest, with clustering in the sense that high activity rates at some time may imply increased rates later, and thus (randomly) greater probability of larger coming events than for periods of lower seismicity. In this case, rate increases have little useful predictive power. Using data from the entire catalogue, the aggregated rate changes before larger events are clearly and strongly statistically significant and cannot be explained by such clustering. To test this we choose events at random from the catalogue as potential "mainshocks''. The events preceding the randomly chosen earthquakes show less pronounced rate increases compared to the observed rate changes prior to larger events. Similar behaviour is observed in data sub-sets. However, statistical confidence decreases for geographical subsets containing few "mainshocks'' as it does when data are weighted such that "mainshocks'' with many preceding events are strongly downweighted relative to those with fewer. The analyses suggest that genuine changes in aggregated rate do occur prior to larger events and that this behaviour is not due to a small number of mainshocks with many preceding events dominating the analysis. It does not automatically follow that it will be possible to routinely observe precursory changes prior to individual larger events, but there is a possibility that this may be feasible, e. g. with better data from more sensitive networks.

    Fulltekst (pdf)
    fulltext
  • 48.
    Adamaki, Angeliki
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Roberts, Roland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Advantages and Limitations of Foreshock Activity as a Useful Tool for Earthquake ForecastingManuskript (preprint) (Annet vitenskapelig)
  • 49.
    Adamaki, Angeliki
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Roberts, Roland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    EVIDENCE OF PRECURSORY PATTERNS IN AGGREGATED TIME SERIES2016Inngår i: Bulletin of the Geological Society of Greece, vol. L, 2016, Proceedings of the 14th Intern. Congress, Thessaloniki, May 2016, 2016, Vol. 50Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We investigate temporal changes in seismic activity observed in the West Corinth Gulfand North-West Peloponnese during 2008 to 2010. Two major earthquake sequencestook place in the area at that time (in 2008 and 2010). Our aim is to analyse Greekseismicity to attempt to confirm the existence or non-existence of seismic precursorsprior to the strongest earthquakes. Perhaps because the area is geologically andtectonically complex, we found that it was not possible to fit the data well using aconsistent Epidemic Type Aftershock Sequence (ETAS) model. Nor could weunambiguously identify foreshocks to individual mainshocks. Therefore we soughtpatterns in aggregated foreshock catalogues. We set a magnitude threshold (M3.5)above which all the earthquakes detected in the study area are considered as“mainshocks”, and we combined all data preceding these into a single foreshockcatalogue. This reveals an increase in seismicity rate not robustly observable forindividual cases. The observed effect is significantly greater than that consistent withstochastic models, including ETAS, thus indicating genuine foreshock activity withpotential useful precursory power, if sufficient data is available, i.e. if the magnitudeof completeness is sufficiently low.

    Fulltekst (pdf)
    fulltext
  • 50. Adamczyk, A.
    et al.
    Malinowski, M.
    Malehmir, Alireza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    High-resolution near-surface velocity model building using full-waveform inversion-a case study from southwest Sweden2014Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 197, nr 3, s. 1693-1704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Full-waveform inversion (FWI) is an iterative optimization technique that provides high-resolution models of subsurface properties. Frequency-domain, acoustic FWI was applied to seismic data acquired over a known quick-clay landslide scar in southwest Sweden. We inverted data from three 2-D seismic profiles, 261-572 m long, two of them shot with small charges of dynamite and one with a sledgehammer. To our best knowledge this is the first published application of FWI to sledgehammer data. Both sources provided data suitable for waveform inversion, the sledgehammer data containing even wider frequency spectrum. Inversion was performed for frequency groups between 27.5 and 43.1 Hz for the explosive data and 27.5-51.0 Hz for the sledgehammer. The lowest inverted frequency was limited by the resonance frequency of the standard 28-Hz geophones used in the survey. High-velocity granitic bedrock in the area is undulated and very shallow (15-100 m below the surface), and exhibits a large P-wave velocity contrast to the overlying normally consolidated sediments. In order to mitigate the non-linearity of the inverse problem we designed a multiscale layer-stripping inversion strategy. Obtained P-wave velocity models allowed to delineate the top of the bedrock and revealed distinct layers within the overlying sediments of clays and coarse-grained materials. Models were verified in an extensive set of validating procedures and used for pre-stack depth migration, which confirmed their robustness.

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