uu.seUppsala University Publications
Change search
Refine search result
1234 1 - 50 of 191
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abdi, Amir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Heinonen, Suvi
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Karinen, Tuomo
    Constraints on the geometry of the Suasselka post-glacial fault, northern Finland, based on reflection seismic imaging2015In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 649, p. 130-138Article in journal (Refereed)
    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.

  • 2.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hedin, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    3D Seismic Interpretation and Forward Modeling: an approach to providing reliable results from 2D seismic data2013In: Proceedings of the 12th Biennial Meeting: Mineral Deposit Research for a High-Tech World / [ed] Johnson, E., 2013, Vol. 1-4, p. 50-53Conference paper (Refereed)
    Abstract [en]

    Accurate 3D interpretations is challenging when only 2D seismic reflection data are available. This can be compensated for by using additional data. Here we present two case studies where 2D seismic reflection data have been used in combination with geological/geophysical data to create and verify 3D interpretations of specific structures targeted for scientific deep drilling and mining. In the first case, a surface geological map and high resolution 2D seismic reflection data were used to create a 3D lithological model of the subsurface structures in an area around a scientific deep drilling site. This model was also compared to results from constrained 3D inverse modeling of gravity data. In the second case, seismic forward ray-trace modeling was used to delineate a massive sulfide ore body by using high resolution 2D seismic reflection data. By comparison of the generated synthetic data with the real data, it was found that the top of the ore body was detected.

  • 3.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ask, Maria
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Revealing the deeper structure of the end-glacial Parvie fault system in northern Sweden by seismic reflection profiling2015In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 6, no 2, p. 621-632Article in journal (Refereed)
    Abstract [en]

    A new seismic reflection survey for imaging deeper levels of the end-glacial Parvie fault system in northern Sweden was acquired in June 2014. The Parvie fault system hosts the largest fault scarp so far documented in northern Scandinavia, both in terms of its length and calculated magnitude of the earthquake that generated it. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east-dipping main fault. In the central section of the fault system, where there is a number of subsidiary faults east of the main Parvie scarp, it has been unclear how the earthquakes relate to the structures mapped at the surface. A seismic profile across the Parvie fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflections. The most pronounced reflectors could be mapped to about 3 km depth. In the new seismic survey, for deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65A degrees east-dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a strongly reflective 60A degrees west-dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km, where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data, we propose potential locations for future boreholes for scientific drilling into the fault system. These boreholes will provide a better understanding of the reflective nature of the fault structures and stress fields along the faults at depth.

  • 4.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Munck, Mie
    Boliden Mines.
    High-resolution 2D seismic imaging and forward modeling of a polymetallic sulfide deposit at Garpenberg, central Sweden2013In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 78, no 6, p. B339-B350Article in journal (Refereed)
    Abstract [en]

    We acquired a high-resolution 2D seismic profile to test the capability of the seismic method in imaging a sulfide ore body at Garpenberg, central Sweden. Delineation of the geologic structures, which surround and host the ore body, is another goal of the survey. Due to the 3D geology of the structures, a cross-dip correction performed to image out-of-the-plane reflections, resulting in a clear high amplitude anomaly at a time and location to that to be expected from near the top of the ore body. Furthermore, DMO processing and migration are applied to the data, providing images of four main reflection groups. The reflections have been interpreted as corresponding to geologic rock units in the area that partly interfere with the potential ore body signal. To further investigate the seismic response of the ore body, forward modeling by ray-tracing is applied using the ore body geometry as mapped by drilling. We use two ray-tracing approaches: standard 3D ray-tracing and an exploding reflector approach. Seven representative samples from the mine area are used to determine P-wave velocities. The measurements show a considerable contrast between the ore body and host rock. By comparing the modeled and observed data, we find that the high amplitude signal in the real seismic section most likely emanates from near the top of one concentrated ore which lies inside the larger mapped ore body that has been modeled as a resource. The base of the ore body is only observed on the synthetic data whereas a signal penetration analysis suggests that the seismic signal penetrated efficiently along the entire survey line. Presence of disseminated ore and lower fold toward the northern end of the profile could be combined reasons that make imaging the base of the ore body difficult.

  • 5.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Gessner, Klaus
    Geol Survey Western Australia, 100 Plain St, East Perth, WA 6004, Australia.
    Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia2016In: Tectonophysics, Vol. 689, p. 56-66Article in journal (Refereed)
    Abstract [en]

    The Murchison domain forms the northwest part of the Youanmi Terrane, a tectonic unit within the Neoarchean Yilgarn Craton in Western Australia. In the Cue-Weld Range area the Murchison domain has experienced a complex magmatic and deformation history that resulted in a transposed array of greenstone belts that host significant iron, gold, and base metal deposits. In this study, we interpret the upper 2 s (about 6 km) of a deep crustal seismic profile TOGA-YU1, near the town of Cue, and correlate rock units and structures in outcrop with corresponding reflections. We performed 3D constant velocity ray-tracing and calculate the corresponding travel times for the reflectionsfor time domain pre-stack and post-stack seismic data. This allows us to link shallow reflections with mafic volcanic rocks of the Glen Group and basaltic rocks of the Polelle Group in outcrop. Based on our interpretation and published geological maps and data, we propose a model in which the local stratigraphy represents a refolded thrust system. To test our hypothesis, we applied 2D acoustic finite difference forward modeling. The corresponding synthetic data were processed in the same way as the acquired data. Comparisons between the acquired and the synthetic data show that the model is consistent with observations. We propose a new model for the subsurface of the Cue-Weld Range area and argue that some of the lithologies in the area are repeated structurally at different levels. Our approach highlights the benefit of imaging and modeling of deep seismic transects to resolve local structural complexity in Archean granite-greenstone terrains.

  • 6. Alcalde, J.
    et al.
    Marti, D.
    Calahorrano, A.
    Marzan, I.
    Ayarza, P.
    Carbonell, R.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Pérez-Estaún, A.
    Active seismic characterization experiments of the Hontomin research facility for geological storage of CO2, Spain2013In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 19, no 0, p. 785-795Article in journal (Refereed)
    Abstract [en]

    An active source seismic experiment was carried out as part of the subsurface characterization study of the first Spanish Underground Research Facility for Geological Storage of CO2 in Hontomín (Burgos, Spain). The characterization experiment included a 36 km2 3D seismic reflection survey and two three-component seismic profiles. The target reservoir is a saline aquifer located at 1450 m depth within Lower Jurassic carbonates (Lias). The main seal is formed by interlayered marlstones and marly limestones of Early to Middle Jurassic age (Dogger and Lias). The seismic images obtained allow defining the 3D underground architecture of the reservoir site. The structure consists of an asymmetric dome crosscut by a relatively complex fault system. The detailed characterization of the fracture system is currently under study to unravel the geometric distribution of the faults and their extent within the different formations that form the structure. The constrained model has guided the design of the injection and monitoring boreholes and provided the data for the baseline study. The resultant high resolution seismic model will be used as a reference in future monitoring stages.

  • 7. Alcalde, J.
    et al.
    Martí, D.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Sopher, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Saura, E.
    Marzán, I.
    Ayarza, P.
    Calahorrano, A.
    Pérez-Estaún, A.
    Carbonell, R.
    3-D reflection seismic imaging of the Hontomin structure in the Basque-Cantabrian Basin (Spain)2013In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 4, no 2, p. 481-496Article in journal (Refereed)
    Abstract [en]

    The Basque-Cantabrian Basin of the northern Iberia Peninsula constitutes a unique example of a major deformation system, featuring a dome structure developed by extensional tectonics followed by compressional reactivation. The occurrence of natural resources in the area and the possibility of establishing a geological storage site for carbon dioxide motivated the acquisition of a 3-D seismic reflection survey in 2010, centered on the Jurassic Hontomin dome. The objectives of this survey were to obtain a geological model of the overall structure and to establish a baseline model for a possible geological CO2 storage site. The 36 km(2) survey included approximately 5000 mixed (Vibroseis and explosives) source points recorded with a 25 m inline source and receiver spacing. The target reservoir is a saline aquifer, at approximately 1450 m depth, encased and sealed by carbonate formations. Acquisition and processing parameters were influenced by the rough topography and relatively complex geology. A strong near-surface velocity inversion is evident in the data, affecting the quality of the data. The resulting 3-D image provides constraints on the key features of the geologic model. The Hontom n structure is interpreted to consist of an approximately 10(7) m(2) large elongated dome with two major (W-E and NW-SE) striking faults bounding it. Preliminary capacity estimates indicate that about 1.2 Gt of CO2 can be stored in the target reservoir.

  • 8. Alcalde, Juan
    et al.
    Marzan, Ignacio
    Saura, Eduard
    Marti, David
    Ayarza, Puy
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Perez-Estaun, Andres
    Carbonell, Ramon
    3D geological characterization of the Hontomin CO2 storage site, Spain: Multidisciplinary approach from seismic, well-log and regional data2014In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 627, p. 6-25Article in journal (Refereed)
    Abstract [en]

    The first Spanish Technological Development plant for CO2 storage is currently under development in Hontomin (Spain), in a fractured carbonate reservoir. The subsurface 3D geological structures of the Hontomin site were interpreted using well-log and 3D seismic reflection data. A shallow low velocity zone affects the wave propagation and decreases the coherency of the underlying seismic reflections, deteriorating the quality of the seismic data, and thus preventing a straightforward seismic interpretation. In order to provide a fully constrained model, a geologically supervised interpretation was carried out. In particular, a conceptual geological model was derived from an exhaustive well-logging analysis. This conceptual model was then improved throughout a detailed seismic facies analysis on selected seismic sections crossing the seismic wells and in consistency with the regional geology, leading to the interpretation of the entire 3D seismic volume. This procedure allowed characterizing nine main geological levels and four main fault sets. Thus, the stratigraphic sequence of the area and the geometries of the subsurface structures were defined. The resulting depth-converted 3D geological model allowed us to estimate a maximum CO2 storage capacity of 5.85 Mt. This work provides a 3D geological model of the Hontomin subsurface, which is a challenging case study of CO2 storage in a complex fractured carbonate reservoir. 

  • 9.
    Andersson, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Dehghannejad, Mahdieh
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ask, Maria
    Carbonatite ring-complexes explained by caldera-style volcanism2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 1677-Article in journal (Refereed)
    Abstract [en]

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alno carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at similar to 3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas.

  • 10.
    Ayarza, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Brown, D
    Alvarez-Marron, J
    Juhlin, Christopher
    Contrasting tectonic history of the are-continent suture in the Southern and Middle Urals: implications for the evolution of the orogen2000In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 157, p. 1065-1076Article in journal (Refereed)
    Abstract [en]

    The Main Uralian Fault has been considered the original arc–continent suture for 2000 km along the Uralide orogen. The symmetry of the tectonic units across it suggested a consistent east-dipping polarity for the palaeosubduction zone, which, together with its topographic and aeromagnetic signature, supported the idea of a single suture. However, several characteristics vary at different latitudes. In the Middle Urals, it is a strike-slip fault zone with moderately deformed and metamorphosed volcanic arc fragments in its hanging wall, and low-grade metamorphic rocks of the East European Craton in its footwall. Here, it has a prominent NNW-trending magnetic signature which cross-cuts north-trending anomalies in its hanging wall, and a pronounced reflection seismic signature that can be traced to the top of the middle crust at c. 5 s. TWT. In the Southern Urals, it is a serpentinite mélange zone of ambiguous kinematics, with a weakly deformed and metamorphosed volcanic arc in its hanging wall, and moderately metamorphosed to high pressure rocks of the East European Craton in its footwall. In this part of the orogen, it has a weak reflection seismic character, and a magnetic signature that parallels that of its hanging wall. On the basis of an integrated analysis of these different data sets, we suggest that the Main Uralian Fault, as it is currently defined, is not a single entity, but rather the original arc–continent suture in the south, and the western strand of a strike-slip fault system that reworked the original suture in the Middle Urals.

  • 11.
    Ayarza, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Brown, D
    Beckholmen, M
    Kimbell, G
    Pechnig, R
    Pevzner, L
    Pevzner, R
    Ayala, C
    Bliznetsov, M
    Glushkov, A
    Rybalka, A
    Integrated geological and geophysical studies in the SG4 borehole area, Tagil Volcanic Arc, Middle Urals: Location of seismic reflectors and source of the reflectivity2000In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 105, no B9, p. 21333-21352Article in journal (Refereed)
    Abstract [en]

    Near-vertical incidence reflection seismic data acquired in the Tagil Volcanic Arc (Middle Urals) show the upper crust to be highly reflective. Two intersecting seismic lines located near the ongoing ∼5400 m deep SG4 borehole show that the main reflectivity strikes approximately N-S and dips ∼35°–55° to the east. Prominent reflections intercept the borehole at ∼1000, ∼1500, 2800–2900, ∼3400, and between ∼4000 and 5400 m, which correspond to intervals of low velocity/low density/low resistivity. The surface projections of these reflections lie parallel to the strike of magnetic anomaly trends. Multioffset vertical seismic profile (VSP) data acquired in the SG4 borehole show a seismic response dominated by P to S reflected converted waves from the moderately east dipping reflectivity and from a set of very steep east dipping reflectors not imaged by the surface data. Modeling of the VSP data constrains the depth at which reflectors intercept the borehole and suggests that the P to S conversions are best explained by low-velocity porous intervals rather than higher-velocity mafic material. The most prominent east dipping reflection on the surface seismic data is only imaged on VSP shots that sample the crust closer to the E-W seismic line. This discrepancy between the VSP and the surface seismic data is attributed to rapid lateral changes in the physical properties of the reflector. Surface and borehole data suggest that the low-velocity/low-density/low-resistivity intervals are the most important source of reflectivity in the SG4 borehole area, although lithological contrasts may also play a role. Drill cores from the these zones contain hydrothermal alteration minerals indicating interaction with fluids. Tectonic criteria suggest that they might represent imbricated fracture zones often bounding different lithologies and/or intrusions. Some of them might also represent high-porosity lava flows or pyroclastic units, common in island arc environments.

  • 12. Ayarza, P.
    et al.
    Martínez Catalán, J. R.
    Alvarez-Marrón, J.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Geophysical constraints on the structure of a limited ocean-continent subduction zone at the north Iberian margin2004In: Tectonics, Vol. 23, p. 1010-Article in journal (Refereed)
    Abstract [en]

     Late Cretaceous to Cenozoic convergence between Iberia and Europe led to the partial closure of the Bay of Biscay with limited southward subduction of oceanic crust below the North Iberian Margin. Inclined sub-Moho reflections and diffractions observed in deep seismic reflection profiles shot across the margin are especially well represented in two reflection profiles: ESCIN-3.2 and ESCIN-3.3. These two profiles have been chosen to test if the sub-Moho reflections correspond to true primary deep events and, provided that they are reflecting off the subduction zone, to investigate its deep structure. Spectral analysis together with travel time estimation and migration allow us to characterize a number of these sub-Moho events as deep-source, low-frequency (∼19 Hz), reflections and diffractions. Synthetic seismograms were generated by three-dimensional seismic modeling of a sub-Moho southward dipping surface, interpreted to correspond to the top of subducted oceanic crust. Comparison between the real and synthetic data show that inclined, low-frequency sub-Moho reflections in both, ESCIN-3.2 and ESCIN-3.3 profiles may correspond to reflections from southward subducted Bay of Biscay oceanic crust. Geoid, free-air gravity, and absolute topography modeling provides additional constraints on the lithospheric-scale structure of this limited ocean-continent subduction zone beneath the North Iberian Margin.

  • 13.
    Bastida, F
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Aller, J
    Puchkov, VN
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Oslianski, A
    A cross-section through the Zilair Nappe (southern Urals)1997In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 276, no 1-4, p. 253-263Article in journal (Other academic)
    Abstract [en]

    A structural transect in the Zilair-Kugarchi area involves the western part of the Suvanyak Complex, the Zilair Nappe and the eastern part of the foreland thrust and fold belt. This section has been analyzed using field, microstructural and seismic data. The cross-section shows the transition from the hinterland to the foreland in the footwall to the suture of the southern Urals. The rocks involved range from early Palaeozoic to Permian in age. A characteristic of the Zilair Nappe is the dominance of a succession of volcanic greywackes and mudrocks of Late Devonian age (Zilair Formation). The metamorphic grade decreases from east to west, from greenschist facies to diagenetic conditions. The structure of the cross-section mainly comprises west-directed thrusts and thrust-related folds with an associated cleavage. Fold vergence changes along the section depending on of the distance to the associated thrust and its geometry. The Zilair thrust which separates the Zilair Nappe from the foreland thrust and fold belt accommodated ca. 10 km displacement and the characteristics of the deformation are similar on both sides of it. The contact between the Zilair Nappe and Suvanyak Complex is a west-dipping normal fault that does not represent a major tectonic boundary.

  • 14. Bauer, Tobias E
    et al.
    Tavakoli, Saman
    Weihed, Pär
    Luleå tekniska universitet.
    Skytta, Pietari
    Hermansson, Tobias
    Allen, Rodney
    Dehghannejad, Mahdieh
    García Juanatey, María de los Ángeles
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    A regional scale 3D-model of the Skellefte mining district, northern Sweden2013In: Proceedings of the 12th SGA Biennial Meeting 2013., Uppsala, 2013, p. 62-65Conference paper (Refereed)
  • 15.
    Bergman, B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Tryggvason, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    High resolution seismic traveltime tomography incorporating static corrections applied to a till covered bedrock environment2004In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 69, p. 1082-1090Article in journal (Refereed)
    Abstract [en]

    A major obstacle in tomographic inversion is near-surface velocity variations. Such shallow velocity variations need to be known and correctly accounted for to obtain images of deeper structures with high resolution and quality. Bedrock cover in many areas consists of unconsolidated sediments and glacial till. To handle the problems associated with this cover, we present a tomographic method that solves for the 3D velocity structure and receiver static corrections simultaneously. We test the method on first-arrival picks from deep seismic reflection data acquired in the mid- late to 1980s in the Siljan Ring area, central Sweden. To use this data set successfully, one needs to handle a number of problems, including time-varying, near-surface velocities from data recorded in winter and summer, several sources and receivers within each inversion cell, varying thickness of the cover layer in each inversion cell, and complex 3D geology. Simultaneous inversion for static corrections and velocity produces a much better image than standard tomography without statics. The velocity model from the simultaneous inversion is superior to the velocity model produced using refraction statics obtained from standard reflection seismic processing prior to inversion. Best results using the simultaneous inversion are obtained when the initial top velocity layer is set to the near-surface bedrock velocity rather than the velocity of the cover. The resulting static calculations may, in the future, be compared to refraction static corrections in standard reflection seismic processing. The preferred final model shows a good correlation with the mapped geology and the airborne magnetic map.

  • 16.
    Bergman, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Palm, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    High-resolution reflection seismic imaging of the upper crust at Laxemar, southeastern Sweden2002In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 355, no 1-4, p. 201-213Article in journal (Refereed)
    Abstract [en]

    A major cost in exploring the upper 1–2 km of crystalline crust with reflection seismics is the drilling required for explosive sources. By reducing the charge size to a minimum, shallow inexpensive shotholes can be drilled with handheld equipment. Here, we present results from a full-scale test using small charges for high-resolution seismic surveying over a nuclear waste disposal study site (not an actual site). Two 2–2.5-km-long crossing profiles were acquired in December 1999 with 10-m shot and geophone spacing in the Laxemar area, near Oskarshamn in southeastern Sweden. After standard processing, including dip moveout (DMO), several subhorizontal to moderately dipping reflections are imaged. Many of the dipping ones can be correlated to fracture zones observed in a ca. 1700-m-deep borehole where the profiles cross and/or to fracture zones mapped on the surface. The imaged fracture zones form a complex 3D pattern illustrating the necessity of having 3D control before interpreting seismic reflection data. Analyses of sonic and density logs from the borehole show that greenstones have significantly higher impedances than the more dominant granite found in the borehole (granite/greenstone reflection coefficient is +0.065). These greenstones may contribute to the reflectivity when associated with fracture zones. In some cases, where they are present as larger subhorizontal lenses, they may be the dominant source of reflectivity. A set of north-dipping (10°) reflectors at 3–3.5-km depth can be correlated to a similar set observed below the island of Ävrö about 3 km to the east.

  • 17.
    Bergman, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Tryggvason, Ari
    Shallow seismic imaging in hard rock environments: An example from the Forsmark potential nuclear waste storage site, SwedenManuscript (Other academic)
  • 18.
    Bergman, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Tryggvason, Ari
    Juhlin, Christopher
    High-resolution seismic traveltime tomography incorporating static corrections applied to a till-covered bedrock environment2004In: Geophysics, ISSN 0016-8033, Vol. 69, no 4, p. 1082-1090Article in journal (Refereed)
  • 19.
    Bergman, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Tryggvason, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Seismic tomography studies of cover thickness and near-surface bedrock velocities2006In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 71, no 6, p. U77-U84Article in journal (Refereed)
    Abstract [en]

    Reflection seismic imaging of the uppermost kilometer of crystalline bedrock is an important component in site surveys for locating potential storage sites for nuclear waste in Sweden. To obtain high-quality images, refraction statics are calculated using first-break travel times. These first-break picks may also be used to produce tomographic velocity images of the uppermost bedrock. In an earlier study, we presented a method applicable to data sets where the vast majority of shots are located in the bedrock below the glacial deposits, or cover, typical for northern latitudes. A by-product of this method was an estimate of the cover thickness from the receiver static that was introduced to sharpen the image. We now present a modified version of this method that is applicable for sources located in or on the cover, the general situation for nuclear waste site surveys. This modified method also solves for 3D velocity structure and static corrections simultaneously in the inversion process. The static corrections can then be used to estimate the cover thickness. First, wetest our tomography method on synthetic data with the shot points in the bedrock below the cover. Next, we develop a strategy for the case when the sources are within the cover. The method is then applied to field data from five crooked-line, high-resolution reflection seismic profiles ranging in length from 2 to 5 km. The crooked-line profiles make the study 2.5 dimensional regarding bedrock velocities. The cover thickness along the profiles varies from 0 to 15 m. Estimated thickness of the cover agrees well with data from boreholes drilled near the profiles. Low-velocity zones in the uppermost bedrock generally correlate with locations where reflections from the stacked sections project to the surface. Thus, the method is functional, both for imaging the uppermost bedrock velocities as well as for estimating the cover thickness.

  • 20. Bergmann, Peter
    et al.
    Diersch, Magdalena
    Götz, Julia
    Ivandic, Monika
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ivanova, Alexandra
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Kummerow, Juliane
    Liebscher, Axel
    Lüth, Stefan
    Meekes, Sjef
    Norden, Ben
    Schmidt-Hattenberger, Cornelia
    Wagner, Florian M.
    Zhang, Fengjiao
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Review on geophysical monitoring of CO2 injection at Ketzin, Germany2016In: Journal of Petroleum Science and Engineering, Vol. 139, p. 112-136Article in journal (Refereed)
    Abstract [en]

    Geophysical monitoring activities were an important component of the CO2 injection program at the Ketzin site, Germany. Here we report on the seismic and electrical resistivity tomography (ERT) measurements performed during the period of the site development and CO2 injection. Details on the site geology, the history of the CO2 injection operation, and petrophysical models relevant for the interpretation of the geophysical data are presented. The seismic measurements comprise 2D and 3D surface seismic surveys, vertical seismic profilings, and crosshole measurements. Apart from the measurements, results from advanced processing methods, such as impedance inversion and full-waveform inversion are also presented. In addition, results from crosshole ERT and surface-downhole ERT are presented. If operational efforts are taken into consideration we conclude that a combination of several geophysical methods is preferable given the demands of a spatiotemporally comprehensive monitoring program. We base this conclusion on that the different imaging characteristics and petrophysical sensitivities of different methods can complement each other. An important finding is, based on signal quality and reduced operational costs, that the use of permanent installations is promising. Generally, specific monitoring layouts will depend on site-specific characteristics, such as reservoir depth, availability of wells, petrophysical characteristics, and accessibility of surface locations. Given the comprehensive range of methods applied, the reported results are not only relevant to the operation of CO2 storage sites, but are also of interest to other monitoring projects dealing with fluid injection or production.

  • 21.
    Bergmann, Peter
    et al.
    GFZ German Research Centre for Geosciences, Centre for Geological Storage, Telegrafenberg, Potsdam, Germany.
    Ivandic, Monika
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Norden, Ben
    GFZ German Research Centre for Geosciences, Reservoir Technologies, Telegrafenberg, Potsdam, Germany..
    Rücker, Carsten
    Technical University Berlin, Department of Applied Geophysics, Berlin, Germany.
    Kiessling, D.
    Lüth, S.
    Schmidt-Hattenberger, Cornelia
    GFZ German Research Centre for Geosciences, Centre for Geological Storage, Telegrafenberg, Potsdam, Germany.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Combination of seismic reflection and constrained resistivity inversion with an application to 4D imaging of the CO2 storage site, Ketzin, Germany2014In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 79, no 2, p. B37-B50Article in journal (Refereed)
    Abstract [en]

    A combination of seismic and geoelectric processing was studied by means of a structurally constrained inversion approach. Structural constraints were interpreted from the seismic data and integrated into the geoelectric inversion through a local regularization, which allowed inverted resistivities to behave discontinuously across defined boundaries. This arranged seismic processing and constrained resistivity inversion in a sequential workflow, making the generic assumption that the petrophysical parameters of both methods change across common lithostructural boundaries. We evaluated the approach using a numerical example and a real data example from the Ketzin CO2 pilot storage site, Germany. The latter demonstrated the efficiency of this approach for combining 4D seismic and surface-downhole geoelectric data. In consistence with the synthetic example, the constrained resistivity inversions produced clearer delineated images along the boundary between caprock and reservoir formation. Near the CO2-flooded reservoir, the seismic and geoelectric time-lapse anomalies correlated well. At some distance to the downhole electrodes, however, the geoelectric images conveyed a notably lower resolution in comparison to the corresponding seismic images. Both methods confirm a northwesterly trend for the CO2 migration at the Ketzin site, although a rather northerly direction was initially expected. The results demonstrate the relevance of the presented approach for the combination of both methods for integrated geophysical CO2 storage monitoring.

  • 22.
    Bergmann, Peter
    et al.
    GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Centre for Geological Storage, Potsdam, Germany.
    Kashubin, Artem
    WesternGeco, Schlumberger House, Buckingham Gate, West Sussex, UK .
    Ivandic, Monika
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lueth, Stefan
    GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Centre for Geological Storage, Potsdam, Germany.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Time-lapse difference static correction using prestack crosscorrelations: 4D seismic image enhancement case from Ketzin2014In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 79, no 6, p. B243-B252Article in journal (Refereed)
    Abstract [en]

    A method for static correction of time-lapse differences in reflection arrival times of time-lapse prestack seismic data is presented. These arrival-time differences are typically caused by changes in the near-surface velocities between the acquisitions and had a detrimental impact on time-lapse seismic imaging. Trace-to-trace time shifts of the data sets from different vintages are determined by crosscorrelations. The time shifts are decomposed in a surface-consistent manner, which yields static corrections that tie the repeat data to the baseline data. Hence, this approach implies that new refraction static corrections for the repeat data sets are unnecessary. The approach is demonstrated on a 4D seismic data set from the Ketzin CO2 pilot storage site, Germany, and is compared with the result of an initial processing that was based on separate refraction static corrections. It is shown that the time-lapse difference static correction approach reduces 4D noise more effectively than separate refraction static corrections and is significantly less labor intensive.

  • 23. Bergmann, Peter
    et al.
    Yang, Can
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lüth, Stefan
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Cosma, Calin
    Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO(2) injection site Ketzin (Germany)2011In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 75, no 1, p. 124-139Article in journal (Refereed)
    Abstract [en]

    The Ketzin project provides an experimental pilot test site for the geological storage of CO(2). Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO(2) had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO(2), and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon.

    Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey.

    Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO(2) related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO(2) signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO(2), as expected, but shows signs of a pressure response in the repeat data.

  • 24.
    Brodic, Bojan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bastani, Mehrdad
    Geological Survey of Sweden.
    Mehta, Suman
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lundberg, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Wang, Shunguo
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Multi-component digital-based seismic landstreamer and boat-towed radio-magnetotelluric acquisition systems for improved subsurface characterization in the urban environment2017In: First Break, ISSN 0263-5046, E-ISSN 1365-2397, Vol. 35, no 8, p. 41-47Article in journal (Other academic)
    Abstract [en]

    It is estimated that urban life will be the norm for around 60% of the world’s population by 2040, leading to a more centralized distribution of people and making the city as the main place of residence (Whiteley, 2009). This population centralization inherently implies rapidly expanding cities and imposes the need for more infrastructure within, around and between the present city boundaries. However, infrastructure projects nowadays have to follow strict civil engineering standards that require detailed knowledge of subsurface conditions during different stages of the construction processes. Since direct methods conventionally used for site characterization (e.g., drilling and/or core testing) are still relatively expensive the focus in the last two decades has been on non-invasive, geophysical methods. However, geophysical site characterization in urban areas is not an easy task owing to numerous challenges and various types of noise sources. Challenges such as electric/electromagnetic (EM) noise, pipelines and other subsurface objects (sometimes even unknown or undocumented), the inability to properly couple sensors because of pavement, traffic noises and limited space are common in urban environment. Since geophysical surveys need to be done with the least amount of disturbances to the environment, residents and traffic, new geophysical techniques for fast, non-invasive and high-resolution site characterization are needed. To overcome some of these challenges, a nationwide joint industry-academia project was launched in 2012 TUST GeoInfra, www.trust-geoinfra.se). As a component in the project, Uppsala University developed two new data acquisition systems. These are a fully digital MEMS-based (Micro-machined Electro-Mechanical Sensor) three component (3C) seismic landstreamer and a boat-towed radio-magnetotelluric (RMT) acquisition system. Both systems were specifically designed to address urban environments with the RMT system particularly aiming at efficient and cost-effective geophysical surveying on shallow-water bodies, which constitute 7% of Scandinavia. In this article, we will describe the two systems and present two case studies illustrating their potential. A number of published accounts are now available from the two systems showing what type of problems they can address (e.g., Bastani et al., 2015; Brodic et al., 2015; Malehmir et al., 2015a, 2015b, 2016a, 2016b, 2017; Dehghannejad et al., 2017; Maries et al., 2017; Mehta et al., 2017; Brodic et al., 2017).

  • 25.
    Brodic, Bojan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    All wave-modes converted and reflected from fracture systems: A tunnel-surface seismic experiment2015Manuscript (preprint) (Other academic)
  • 26.
    Brodic, Bojan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bedrock and Fracture Zone Delineation UsingDifferent Near-surface Seismic Sources2017Conference paper (Other academic)
    Abstract [en]

    To delineate the bedrock surface and a fracture zone intersected by a well at c. 50 m depth, a seismic survey wasconducted using four different near-surface seismic sources. These were a 5-kg sledgehammer, a metal I-beamhit laterally, an accelerated weight drop and a prototype source tested for the first time called Udarnik. TheUdarnik source has two hammers whose impacts are initiated by an electromagnetic force of the stable coilexciting its inner moving part. Two hammers separated by a distance of approximately 50 cm successively hittwo contact plates mounted on the bottom of the source. The sweep length is adjustable and maximum 18 hitscan be made per second. In this study, we compare the performance of every source used and present reflectionseismic sections and tomography results from the high-fold (star-type acquisition was used) combinedlandstreamer and wireless recorder survey. Preliminary results indicate that bedrock was well delineated both ontomography results and stacked sections for all sources and some weak reflectivity is observed where thefracture zone is expected with most of the sources used showing the potential of the seismic methods forfracture zone imaging and near-surface characterization

  • 27.
    Brodic, Bojan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Delineating fracture zones using surface-tunnel-surfaceseismic data, P-S, and S-P mode conversions2017In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 122, no 7, p. 5493-5516Article in journal (Refereed)
    Abstract [en]

    A surface-tunnel-surface seismic experiment was conducted at the Äspö Hard Rock Laboratoryto study the seismic response of major fracture systems intersecting the tunnel. A newly developedthree-component microelectromechanical sensor-based seismic landstreamer was deployed inside the noisytunnel along with conventional seismic receivers. In addition to these, wireless recorders were placed on thesurface. This combination enabled simultaneous recording of the seismic wavefield both inside the tunneland on the surface. The landstreamer was positioned between two geophone-based line segments, alongthe interval where known fracture systems intersect the tunnel. First arrival tomography produced a velocitymodel of the rock mass between the tunnel and the surface with anomalous low-velocity zones correlatingwell with locations of known fracture systems. Prominent wave mode converted direct and reflected signals,P-S and S-P waves, were observed in numerous source gathers recorded inside the tunnel. Forward traveltime and 2-D finite difference elastic modeling, based on the known geometry of the fracture systems, showthat the converted waves are generated at these systems. Additionally, the landstreamer data were used toestimate Vp/Vs, Poisson’s ratio, and seismic attenuation factors (Qp and Qs) over fracture sets that havedifferent hydraulic conductivities. The low-conductivity fracture sets have greater reductions in P wavevelocities and Poisson’s ratio and are more attenuating than the highly hydraulically conductive fracture set.Our investigations contribute to fracture zone characterization on a scale corresponding to seismicexploration wavelengths.

  • 28.
    Brodic, Bojan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Dynesius, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bastani, Mehrdad
    Palm, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Multicomponent broadband digital-based seismic landstreamer for near-surface applications2015In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 123, p. 227-241Article in journal (Refereed)
    Abstract [en]

    During the last few decades there has been an increased demand for infrastructure, along with a greater awareness of environmental issues in the construction industry. These factors have contributed to an increased interest in using seismic methods for near surface characterization, particularly in urban environments. Seismic sensors not affected by anthropogenic electromagnetic noise are therefore important, as well as an acquisition system that is easy to deploy, move and non-invasive. To address some of these challenges, a multicomponent broadband MEMS (micro-electro mechanical system) based landstreamer system was developed. The landstreamer system is fully digital, therefore it is less sensitive to electrical or electromagnetic noise. Crosstalk, leakage and tilting tests show that the system is superior to its predecessors. The broadband nature of the sensors (theoretically 0–800 Hz), 3C (three-component) recording and the close spacing of the sensors enable high-resolution imaging. The current streamer configuration consists of 20 sensors 4 m apart and 80 sensors 2 m apart. The streamer can easily be combined with wireless recorders for simultaneous data acquisition. In this study, we present results from testing of the streamer with various sources, such as a shear wave vibrator and different types of impact sources. MEMS-sensors and their high sensitivity allowed recording clear reflections that were not observed with coil-based sensors. A complementary test was also carried out at a planned access ramp for an urban tunnel where potential poor quality rocks had been identified by drilling. First-break traveltime tomography showed that these poor quality rocks correlate with low velocity zones. The presented landstreamer system has great potential for characterizing the subsurface in noisy environments.

  • 29.
    Brown, D
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, C
    Alvarez-Marron, J
    Perez-Estaun, A
    Oslianski, A
    Crustal-scale structure and evolution of an arc-continent collision zone in the southern Urals, Russia1998In: Tectonics, ISSN 0278-7407, E-ISSN 1944-9194, Vol. 17, no 2, p. 158-171Article in journal (Other academic)
    Abstract [en]

    The outcropping geology of the southern Urals contains a well-preserved accretionary complex related to the Paleozoic collision that took place between the Magnitogorsk arc and the former East European Craton. The crustal-scale structure of the accretionary complex has been determined from outcropping field geology that is integrated with three reflection seismic profiles. The reflection profiles show the accretionary complex to be highly reflective, allowing direct comparison of many reflections with surface geological features. We interpret the accretionary complex to be a thrust stack that is composed of shallowly subducted continental shelf and rise material, syncollisional sediments derived from the arc, deeply subducted high-pressure gneisses that are intercalated with eclogites and blueschist, and, at the highest structural level, ophiolite complexes. It is bound at the base by a thrust and at the rear by a highly deformed zone (the Main Uralian fault) adjacent to the backstop (the Magnitogorsk arc). Deposition of the Late Devonian volcaniclastic sediments of the Zilair Formation appears to be related to collision, uplift, and erosion of the arc, possibly following the arrival of the full thickness of the East European Craton continental crust at the subduction zone. With the arrival of the continental crust at the subduction zone, offscraping and underplating of Paleozoic slope and platform material took place at the base of the accretionary complex. Uplift of the arc was followed by its collapse and the unconformable deposition of Lower Carboniferous shallow water carbonates on top of it. A time lag of 10 - 15 Myr occurred between the high-pressure metamorphism and the subsequent arrival of the East European Craton at the subduction zone.

  • 30. Brown, D
    et al.
    Juhlin, C
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Puchkov, V
    Orogenic Processes in the Uralides: Introduction2002In: Orogenic Processes in the Paleozoic Uralides, American Geophysical Union , 2002, p. 1-7Chapter in book (Refereed)
  • 31. Brown, D
    et al.
    Juhlin, C
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Tryggvason, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Steer, D
    Ayarza, P
    Beckholmen, M
    Rybalka, A
    Bliznetsov, M
    The Crustal Architecture of the Southern and Middle Urals from the URSEIS, ESRU, and Alapaev Reflection Seismic Profiles2002In: Orogenic Processes in the Paleozoic Uralides, American Geophysical Union , 2002, p. 33-48Chapter in book (Refereed)
  • 32. Brown, D.
    et al.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ayala, C.
    Tryggvason, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Bea, F.
    Alvarez-Marron, J.
    Carbonell, R.
    Seward, D.
    Glasmacher, U.
    Puchkov, V.
    Perez-Estaun, A.
    Mountain building processes during continent-continent collision in the Uralides2008In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, ISSN 0012-8252, Vol. 89, no 3-4, p. 177-195Article in journal (Refereed)
    Abstract [en]

    Since the early 1990's the Paleozoic Uralide Orogen of Russia has been the target of a significant research initiative as part of EUROPROBE and GEODE, both European Science Foundation programmes. One of the main objectives of these research programmes was the determination of the tectonic processes that went into the formation of the orogen. In this review paper we focus on the Late Paleozoic continent-continent collision that took place between Laurussia and Kazakhstania. Research in the Uralides was concentrated around two deep seismic profiles crossing the orogen. These were accompanied by geological, geophysical, geochronological, geochemical, and low-temperature thermochronological studies. The seismic profiles demonstrate that the Uralides has an overall bivergent structural architecture, but with significantly different reflectivity characteristics from one tectonic zone to another. The integration of other types of data sets with the seismic data allows us to interpret what tectonic processes where responsible for the formation of the structural architecture, and when they were active. On the basis of these data, we suggest that the changes in the crustal-scale structural architecture indicate that there was significant partitioning of tectonothermal conditions and deformation from zone to zone across major fault systems, and between the lower and upper crust. Also, a number of the structural features revealed in the bivergent architecture of the orogen formed either in the Neoproterozoic or in the Paleozoic, prior to continent-continent collision. From the end of continent-continent collision to the present, low-temperature thermochronology suggests that the evolution of the Uralides has been dominated by erosion and slow exhumation. Despite some evidence for more recent topographic uplift, it has so far proven difficult to quantify it.

  • 33. Brown, D.
    et al.
    Spadea, P.
    Puchkov, V.
    Alvarez-Marron, J.
    Herrington, R.
    Willner, A.P.
    Hetzel, R.
    Gorozhanina, Y.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. Geofysik.
    Arc-continent collision in the Southern Urals2006In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 79, no 3-4, p. 261-287Article in journal (Refereed)
    Abstract [en]

    The Southern Urals of Russia contain what is arguably one of the best-preserved examples of an arc–continent collision in anyPaleozoic orogen. The arc–continent collision history recorded in the rocks of the Southern Urals began in the Early Devonian withthe onset of intra-oceanic subduction and the formation of the Magnitogorsk Arc and ended with its collision with the margin ofBaltica during the Late Devonian. The Baltica margin consisted of a basement that was composed predominantly of rocks ofArchean and Proterozoic age that, by the time of arc–continent collision, was overlain by Cambrian, Ordovician, Silurian, andDevonian sediments interpreted to have been deposited in rift-related grabens on the continental slope and rise, and on the shallowmarine platform. The Magnitogorsk Arc consists of Early to Late Devonian island arc volcanic rocks and overlying volcaniclasticsediments. Arc–continent collision led to the development of an accretionary complex that includes shallowly and deeplysubducted continental margin rocks, ophiolite fragments, and sediments that were deposited in a foreland-basin setting. Thegeochemistry of the Magnitogorsk Arc volcanic rocks, the structure of the arc–continent collision accretionary complex and theforearc, the high-pressure rocks beneath and along the suture zone, the mafic and ultramafic ophiolitic material, and the syn-tectonic sediments show that the Paleozoic tectonic processes recorded in the Southern Urals can be favorably compared with thosein currently active settings such as the west Pacific.© 2006 Elsevier B.V. All rights reserved.

  • 34. Brown, D.
    et al.
    Zhang, X.
    Palomeras, I.
    Simancas, F.
    Carbonell, R.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Salisbury, M.
    Petrophysical analysis of a mid-crustal reflector in the IBERSEIS profile, SW Spain2012In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 550, p. 35-46Article in journal (Refereed)
    Abstract [en]

    The origin of strong crustal reflectors in vertical incidence reflection seismic data is generally attributed to either rock layering, deformation fabrics in shear zones, fluids, or igneous intrusions. The IBERSEIS normal incidence reflection and wide-angle seismic profiles in SW Spain imaged a large, high velocity, subhorizontal reflector in the middle crust (the IBERSEIS Reflective Body) whose origin has been attributed to a mafic intrusion. In order to test this hypothesis, in this paper we present laboratory measurements of Vp, Vs, and density from 17 samples of mafic igneous and metamorphic rocks, and metasediments that are thought to be equivalent to the proposed IBERSEIS Reflective Body. These measurements are then corrected to 400 degrees C at 600 MPa and used to calculate Poisson's ratio and to compare it, Vp, and Vs to values measured in situ by wide-angle data. Finally, normal incidence reflection coefficients are calculated to test if the measured lithologies could reproduce the reflectivity imaged in the vertical incidence reflection seismic data for the IBERSEIS Reflective Body. Our physical property measurements are very similar to those modeled from the wide-angle data, and our reflection coefficients are sufficiently high to cause strong mid-crustal reflectivity. Our data indicate, therefore, that previous interpretations of the IBERSEIS Reflective Body as a mafic sill are quite reasonable.

  • 35. Brown, Dennis
    et al.
    Juhlin, Christopher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics.
    A possible lower crustal flow channel in the Middle Urals based on reflection seismic data2006In: Terra Nova, Vol. 18, p. 1-18Article in journal (Refereed)
  • 36. Brown, Dennis
    et al.
    Juhlin, Christopher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics.
    Tryggvason, Ari
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics.
    Friberg, Magnus
    Rybalka, Alexander
    Puchkov, Viktor
    Gosha, Petrov
    Structural architecture of the Southern and Middle Urals foreland from reflection seismic profiles2006In: Tectonics, ISSN doi:10.1029/2005TC001834, Vol. 25, p. 1002.-Article in journal (Refereed)
  • 37.
    Buntin, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malinowski, Michal
    Polish Academy of Sciences.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Thybo, Hans
    University of Copenhagen, Denmark.
    Buske, Stefan
    TUBAF, Germany.
    Seismic reprocessing of the BABEL lines for improved interpretation of the whole crust – preliminary results2016In: Lithosphere 2016: Ninth Symposium On Structure, Composition And Evolution Of The Lithosphere In Fennoscandia / [ed] Ilmo Kukkonen, Suvi Heinonen, Kati Oinonen, Katriina Arhe, Olav Eklund, Fredrik Karell, Elena Kozlovskaya, Arto Luttinen, Raimo Lahtinen, Juha Lunkka, Vesa Nykänen, Markku Poutanen , Eija Tanskanen and Timo Tiira, Helsinki, Finland: University of Helsinki, Institute of Seismology , 2016, p. 9-12Conference paper (Refereed)
    Abstract [en]

    This ongoing study focuses on the reprocessing of the historical BABEL (Baltic and Bothnian Echoes from the Lithosphere, 1989) seismic lines in the Bay of Bothnia in preparation for the acquisition of a 400 km long onshore reflection and refraction profile in central part of Sweden. The main aim of the project is to increase the understanding of the tectonic evolution of the mineral-rich Bergslagen region both offshore and onshore. The seismic data have been recovered and currently being reprocessed using up-to-date processing methods and preliminary results show promising outcome from this work.

  • 38.
    Can, Yang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Kazemeini, Sayed Hesammoddin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Wenfang, Fan
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Dameng, Liu
    Amplitude Variation with Offset Responses Modeling Study of Walkaway Vertical Seismic Profile Data at CO(2) Geological Storage Site, Ketzin, Germany2011In: Acta Geologica Sinica, ISSN 1000-9515, E-ISSN 1755-6724, Vol. 85, no 5, p. 1118-1126Article in journal (Refereed)
    Abstract [en]

    An important component of any CO(2) sequestration project is seismic monitoring for tracking changes in subsurface physical properties, such as velocity and density. Different reservoirs have different amplitude variation with offset (AVO) responses, which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile (VSP) AVO response to CO(2) injection at the Ketzin site, the first European onshore CO(2) sequestration pilot study dealing with research on geological storage of CO(2). First, we performed rock physics analysis to evaluate the effect of injected CO(2) on seismic velocity using the Biot-Gassmann equation. On the basis of this model, the seismic response for different CO(2) injection saturation was studied using ray tracing modeling. We then created synthetic walkaway VSP data, which we then processed. In contrast, synthetic seismic traces were created from borehole data. Finally, we found that the amplitude of CO(2) injected sand layer with different gas saturations were increased with the offset when compared with the original brine target layer. This is the typical class III AVO anomaly for gas sand layer. The AVO responses matched the synthetic seismic traces very well. Therefore, walkaway VSP AVO response can monitor CO(2) distribution in the Ketzin area.

  • 39. Carbonell, R.
    et al.
    Simancas, J.F.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Pous, J.
    Pérez Estaún, A.
    González Lodeiro, F.
    Muñoz, G.
    Heise, W.
    Ayarza, P.
    Geophysical Evidence of a Mantle Plume Derived Intrusion Complex2004In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 31, p. L11601-Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Deep seismic reflection data acquired as part of the SW-Iberia EUROPROBE project across the transpressional Variscan orogen sample three tectonic terranes: the South Portuguese Zone, the Ossa-Morena Zone, and the Central Iberian Zone. The seismic data reveal the existence of a mid-crustal reflective body 140 km long and of variable thickness (up to 5 km), the Iberian Reflective body. The conductivity image provided by coincident MT soundings, the amplitude characteristics of the seismics, mineralization studies related to magmatic ore deposits, and the surface geology suggest that the IRB is a mantle-derived mafic intrusion. The geophysical, geological and petrological data suggest that the IRB is most probably an Early Carboniferous (approximately at 350–340 Ma) mantle-derived intrusion possibly linked to plume activity that took place in Europe in the Carboniferous and Permian.

  • 40.
    Dehghannejad, M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Weihed, P.
    Luleå University of Technology.
    High-resolution reflection seismic imaging in the Kristineberg mining area, Northern Sweden2010In: Society of Petroleum Engineers - 72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010 - Incorporating SPE EUROPEC 2010, Barcelona: Curran Associates, Inc., 2010, Vol. 7, p. 5368-5371Conference paper (Refereed)
    Abstract [en]

    The Kristineberg mining area is located in the western part of the Skellefte Ore District, one of the most important mining districts in Europe. As a part of a 4D geologic modeling project, two new reflection seismic profiles were acquired. Although the structural geology is complex, the processed seismic data reveal a series of steeply dipping to sub-horizontal reflections, some of which reach the surface and allow correlation with surface geology. Reflection modeling was carried out to obtain the 3D orientation of the main reflections and to provide insight into the possible contribution of out-of-the-plane reflections. The new reflection seismic profiles have improved our understanding of shallow geological structures in the area and in conjunction with recently acquired potential field data, magnetotelluric data and geological observations will help to refine previous 3D geologic modeling interpretations that were aimed at larger scale structures.

  • 41.
    Dehghannejad, Mahdieh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bauer, Tobias E.
    Division of Geosciences, Luleå University of Technology, Sweden.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Weihed, Pär
    Division of Geosciences, Luleå University of Technology, Sweden.
    Crustal geometry of the central Skellefte district, northern Sweden – constraints from reflection seismic investigations2012In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 524, p. 87-99Article in journal (Refereed)
    Abstract [en]

    The Palaeoproterozoic Skellefte mining district in Sweden is one of the most important mining districts in Europe. As a part of a 4D geologic modeling project, three new sub-parallel reflection seismic profiles, with a total length of about 95 km, were acquired in the central part of the district. Processed seismic data reveal a series of gentle- to steeply- dipping reflections and a series of diffraction packages. The majority of reflections that extend to the surface can be correlated with geological features either observed in the field or interpreted from the aeromagnetic map. A set of south-dipping reflections represent inferred syn-extensional listric extensional faults that were inverted during subsequent crustal-shortening. Cross-cutting northdipping reflections are correlated to late-compressional break-back faults. Flat-lying reflections in the central parts of the study area could represent lithological contacts within the Skellefte Group, or the contact between Skellefte Group rocks and their unknown basement. Flat-lying reflections occurring further north are inferred to originate from the top of the Jörn intrusive complex or an intrusive contact within it. So far unknown south- and north-dipping faults have been identified in the vicinity of the Maurliden deposit. Based on the seismic results, a preliminary 3D-model has been created in order to visualize the fault pattern and to provide a base for future 3D/4D modeling in the Skellefte district.

  • 42.
    Dehghannejad, Mahdieh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    García Juanatey, María de los Ángeles
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Skytta, Pietari
    Bauer, Tobias E
    Weihed, Par
    Reflection seismic imaging in the Skellefte ore district, northern Sweden2013In: Mineral depostits for a high-tech world: Proceedings of the 12th SGA Biennial Meeting 2013, Uppsala: Sveriges Geologiska Undersökning , 2013, p. 126-129Conference paper (Refereed)
  • 43.
    Dehghannejad, Mahdieh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Skyttä, Pietari
    Division of Ore Geology, Luleå University of Technology, Luleå, Sweden.
    Weihed, Pär
    Division of Ore Geology, Luleå University of Technology, Luleå, Sweden.
    Reflection seismic imaging of the upper crust in the Kristineberg mining area, northern Sweden2010In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 71, no 4, p. 125-136Article in journal (Refereed)
    Abstract [en]

    The Kristineberg mining area is located in the western part of the Palaeoproterozoic Skellefte Ore District, one of the most important mining districts in Europe. As a part of a 3D geologic modeling project, two new reflection seismic profiles were acquired with a total length of about 20 km. One profile (HR), parallel to previous seismic profiles, was acquired using a 10 m receiver and source interval and crosses the steeply dipping structures of the Kristineberg mine. The other profile (Profile 2) runs perpendicular to all existing profiles in the area. Although the structural geology is complex, the processed seismic data reveal a series of steeply dipping to sub-horizontal reflections, some of which reach the surface and allow correlation with surface geology. Our general interpretation of the seismic images is that the Kristineberg mine and associated mineral horizon are located in the northern part of a series of steeply south dipping structures. Overall, main structures plunge to the west at about 30 degrees-40 degrees. Cross-dip analysis and reflection modeling were carried out to obtain the 3D orientation of the main reflections and to provide insight into the possible contribution of out-of-the-plane reflections. This helped, for example, to obtain the 3D geometry of a deep reflection that was previously interpreted as structural basement to volcanic rocks. The new reflection seismic profiles have improved our understanding of shallow geological structures in the area and in conjunction with recently acquired potential field data, magnetotelluric data and geological observations will help to refine previous 3D geologic modeling interpretations that were aimed at larger scale structures.

  • 44.
    Dehghannejad, Mahdieh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Skytta, Pietari
    Division of Ore Geology, Luleå University of Technology, Luleå, Sweden.
    3D constraints and finite-difference modeling of massive sulfide deposits: The Kristineberg seismic lines revisited, northern Sweden2012In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 77, no 5, p. WC69-WC79Article in journal (Refereed)
    Abstract [en]

    The Kristineberg mining area in the western part of the Skellefte ore district is the largest base metal producer in northern Sweden and currently the subject of extensive geophysical and geologic studies aimed at constructing 3D geologic models. Seismic reflection data form the backbone of the geologic modeling in the study area. A geologic cross section close to the Kristineberg mine was used to generate synthetic seismic data using acoustic and elastic finite-difference algorithms to provide further insight about the nature of reflections and processing challenges when attempting to image the steeply dipping structures within the study area. Synthetic data suggest processing artifacts manifested themselves in the final 2D images as steeply dipping events that could be confused with reflections. Fewer artifacts are observed when the data are processed using prestack time migration. Prestack time migration also was performed on high-resolution seismic data recently collected near the Kristineberg mine and helped to image a high-amplitude, gently dipping reflection occurring stratigraphically above the extension of the deepest Kristineberg deposit. Swath 3D processing was applied to two crossing seismic lines, west of the Kristineberg mine, to provide information on the 3D geometry of an apparently flat-lying reflection observed in both of the profiles. The processing indicated that the reflection dips about 30 degrees to the southwest and is generated at the contact between metasedimentary and metavolcanic rocks, the upper part of the latter unit being the most typical stratigraphic level for the massive sulfide deposits in the Skellefte district.

  • 45.
    Doughty, Christine
    et al.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA..
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA..
    Rosberg, Jan-Erik
    Lund Univ, Lund, Sweden..
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Dobson, Patrick F.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA..
    Birkholzer, Jens T.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA..
    Flowing fluid electrical conductivity logging of a deep borehole during and following drilling: estimation of transmissivity, water salinity and hydraulic head of conductive zones2017In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 25, no 2, p. 501-517Article in journal (Refereed)
    Abstract [en]

    Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at re, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet providing important information on depths of hydraulically conductive zones and their transmissivities and salinities. This paper presents a reanalysis of this set of data together with a new FFEC logging data set obtained soon after drilling was completed, also over a period of 1 day, but with a different pumping rate and water-level drawdown. Their joint analysis not only results in better estimates of transmissivity and salinity in the conducting fractures intercepted by the borehole, but also yields the hydraulic head values of these fractures, an important piece of information for the understanding of hydraulic structure of the subsurface. Two additional FFEC logging tests were done about 1 year later, and are used to confirm and refine this analysis. Results show that from 250 to 2,000 m depths, there are seven distinct hydraulically conductive zones with different hydraulic heads and low transmissivity values. For the final test, conducted with a much smaller water-level drawdown, inflow ceased from some of the conductive zones, confirming that their hydraulic heads are below the hydraulic head measured in the wellbore under non-pumped conditions. The challenges accompanying 1-day FFEC logging are summarized, along with lessons learned in addressing them.

  • 46. Foerster, A.
    et al.
    Giese, R.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Norden, B.
    Springer, N.
    The Geology of the CO2SINK Site: From Regional Scale to Laboratory Scale2009In: GREENHOUSE GAS CONTROL TECHNOLOGIES 9, 2009, Vol. 1, p. 2911-2918Conference paper (Other academic)
    Abstract [en]

    Here we report on the framework of geological site exploration, which encompassed investigations at different scales prior to and after the drilling of the three CO2SINK boreholes. Past and new exploration data are integrated to delineate at regional scale (1) the geological structure of CO2 storage formation and its overburden, including fault systems as potential fluid pathways and (2) the shallow hydrogeology and the groundwater flow directions for an assessment of effects in case of CO2 leakage and migration. The poro-perm facies and mineralogical composition of the CO2 reservoir rock and the top seal formation were studied by routine and special core analyses, including the measurement of porosity, gas and brine permeability, and by XRD analysis. (C) 2009 Elsevier Ltd. All rights reserved.

  • 47.
    Frenje, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Scattering attenuation: 2-D and 3-D finite difference simulations vs. theory2000In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 44, no 1, p. 33-46Article in journal (Refereed)
    Abstract [en]

    Scattering of seismic waves is studied by producing synthetic vertical seismic profiling (VSP) seismograms with 2-D and 3-D finite difference modelling in random media. The random models used are Gaussian and band-limited self-similar, or fractal random media. The modelling is performed acoustically, but we believe that, considering the geometry of this study, the results obtained will hold for the elastic case as well.

    Properties of the random media are discussed, in particular the difference between discrete and continuous media, and the importance of this difference. We show that when using the band-limited Von Karman correlation function when generating the random medium, the size of the model should be greater than 2πa, where a is the correlation distance, and the grid spacing should be less then a. If not, the medium will not have the proper characteristics.

    Analytical expressions for scattering attenuation, derived from single scattering theory, can be used to estimate scattering Q from borehole velocity logs, if it is known what minimum scattering angle, θmin, to use. θmin, the minimum angle energy, must be scattered to be regarded as not contributing to the propagating wave. We estimate θmin by comparing Q values estimated from our synthetic VSP seismograms with the analytical expressions. The comparison also shows when the assumption of single scattering is valid. Previous studies in 2-D give a θmin of ∼30°. In this paper, we make a comparison for both the 2-D and 3-D cases, and show that the Q estimate is highly sensitive to how the analysis is done. We show that single scattering theory agrees well with finite difference simulations for self-similar media with low Hurst numbers, but with a somewhat lower θmin of 10–20°. This holds for a range of correlation lengths, a, including the case of infinite, or absence of, a. For Gaussian and exponential media, simulations and theory agree as well with θmin of 10–20°, but only for ka<5, where k is the wave number of the source. For ka>5, simulations and theory diverge, and single scattering theory cannot explain the amplitude attenuation observed in the scattering simulations for these types of media, indicating that it may be difficult to estimate the fractal properties of a medium from seismic data alone.

    With the difficulties of characterizing the scattering medium, and to estimate the scattering attenuation in the simple case of synthetic data with pure scattering, we conclude that it may be difficult to separate scattering and intrinsic attenuation from real data.

  • 48.
    Frenje, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Scattering of seismic waves simulated by finite difference modelling in random media: application to the Gravberg-1 well, Sweden1998In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 293, no 1-2, p. 61-68Article in journal (Refereed)
    Abstract [en]

    We generate surface and VSP synthetic seismograms using finite difference modelling of the elastic wave equation in self-similar media. The elastic model is determined by analyses of the sonic log from the deep Gravberg-1 borehole in central Sweden. The upper 1200 m is highly fractured and the velocities are best described by a log-normal distribution rather than a Gaussian distribution. Analyses of this interval after removing the deterministic trend and assuming a self-similar Gaussian distribution of the random component give a standard deviation of 370 m/s, a correlation distance of 45 m and a Hurst number of 0.18. These values and others from deeper levels are used to generate the 2-D elastic model and the synthetic seismograms are compared with real data. Synthetic surface seismic data show a poor qualitative match when compared to real data. Synthetic VSP data match the real VSP better qualitatively. In general, the synthetic data show considerably more scattering effects than the real data. Possible explanations for this discrepancy include: (1) intrinsic attenuation has been ignored; (2) a Gaussian distribution of the random component was assumed; or (3) the heterogeneities have a preferred orientation. The poor match implies that the method for extracting the 2-D or 3-D velocity variations in the uppermost crust from 1-D sonic log data need to be studied further.

  • 49. Friberg, M
    et al.
    Juhlin, C
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
    Beckholmen, M
    Petrov, M
    Green, AG
    Palaeozoic tectonic evolution of the Middle Urals in the light of the ESRU seismic experiments2002In: J. Geol. Soc. London, Vol. 159, p. 295-306Article in journal (Refereed)
  • 50.
    Friberg, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Green, AG
    Horstmeyer, H
    Roth, J
    Rybalka, A
    Bliznetsov, M
    Europrobe seismic reflection profiling across the eastern Middle Urals and West Siberian Basin2001In: Terra Nova, ISSN 0954-4879, E-ISSN 1365-3121, ISSN 0954-4879, Vol. 12, no 6, p. 252-257Article in journal (Refereed)
    Abstract [en]

    New deep seismic reflection data provide images of the crust and uppermost mantle underlying the eastern Middle Urals and adjacent West Siberian Basin. Distinct truncations of reflections delineate the late-orogenic strike-slip Sisert Fault extending vertically to ∼28 km depth, and two gently E-dipping reflection zones, traceable to 15–18 km depth, probably represent normal faults associated with the opening of the West Siberian Basin. A possible remnant Palaeozoic subduction zone in the lower crust under the West Siberian Basin is visible as a gently SW-dipping zone of pronounced reflectivity truncated by the Moho. Continuity of shallow to intermediate-depth reflections suggest that Palaeozoic accreted island-arc terranes and overlying molasse sequences exposed in the hinterland of the Urals form the basement for Triassic and younger deposits in the West Siberian Basin. A highly reflective lower crust overlies a transparent mantle at about 43 km depth along the entire 100 km long seismic reflection section, suggesting that the lower crust and Moho below the eastern Middle Urals and West Siberian Basin have the same origin.

1234 1 - 50 of 191
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf