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Dynesius, L
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Publications (4 of 4) Show all publications
Wang, S., Bastani, M., Kalscheuer, T., Malehmir, A. & Dynesius, L. (2017). Controlled Source Boat-towed Radio-magnetotellurics for Site Investigation at Äspö Hard Rock Laboratory, Southeastern Sweden. In: : . Paper presented at 79th EAGE Conference and Exhibition, 12–15 June 2017, Paris, France (pp. 1-5).
Open this publication in new window or tab >>Controlled Source Boat-towed Radio-magnetotellurics for Site Investigation at Äspö Hard Rock Laboratory, Southeastern Sweden
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2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The radio-magnetotelluric (RMT) method has traditionally been used for land investigations. However, with the development of the boat-towed RMT system, this method is used on shallow water. The lowest frequency of the RMT method is about 14 kHz and in addition water resistivity is quite low in some cases, therefore controlled source measurements is naturally considered for data acquisition. In order to resolve a fracture zone under a brackish water body, the controlled source boat-towed RMT (CSRMT) approach was tested. CSRMT and RMT one-dimensional inversions were carried out separately to analyze galvanic distortions and source effects in our dataset. Serious distortions observed in both inversions as well as the two-dimensional (2D) structure observed in our previous study made us consider 2D inversion for modeling the data. Due to the sufficiently large distance between transmitter and receivers, the CSRMT data were inverted using a 2D inversion code originally designed for plane-wave RMT data. Occam and damped Occam schemes were used in our 2D inversions for CSRMT and RMT data. The results show that CSRMT can better resolve the fracture zone than RMT. This study further illustrates the use of the boat-towed RMT system and particularly when combined with controlled source.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-325421 (URN)10.3997/2214-4609.201700565 (DOI)
Conference
79th EAGE Conference and Exhibition, 12–15 June 2017, Paris, France
Available from: 2017-06-23 Created: 2017-06-23 Last updated: 2018-06-04Bibliographically approved
Brodic, B., Malehmir, A., Juhlin, C., Dynesius, L., Bastani, M. & Palm, H. (2015). Multicomponent broadband digital-based seismic landstreamer for near-surface applications. Journal of Applied Geophysics, 123, 227-241
Open this publication in new window or tab >>Multicomponent broadband digital-based seismic landstreamer for near-surface applications
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2015 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 123, p. 227-241Article in journal (Refereed) Published
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.

Keywords
Landstreamer, MEMS, Tomography, Near-surface, Urban environment
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-267390 (URN)10.1016/j.jappgeo.2015.10.009 (DOI)000366073400022 ()
Funder
Swedish Research Council Formas, 252-2012-1907
Available from: 2015-11-21 Created: 2015-11-21 Last updated: 2017-12-10Bibliographically approved
Malehmir, A., Wang, S., Lamminen, J., Bastani, M., Juhlin, C., Vaittinen, K., . . . Palm, H. (2014). High-resolution Multicomponent Hardrock Seismic Imaging of Mineral Deposits and their Host Rock Structures. In: : . Paper presented at 76th EAGE Conference & Exhibition 2014, 16-19 June 2014 Amsterdam RAI, The Netherlands.
Open this publication in new window or tab >>High-resolution Multicomponent Hardrock Seismic Imaging of Mineral Deposits and their Host Rock Structures
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2014 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Although applied in the past, there are only a few cases demonstrating the advantages of multicomponentseismic data for mineral exploration. To illustrate this, a test survey using sixty 3C-digital sensors, spacedbetween 2 to 4 m and assembled in a 160 m long landstreamer, was carried out to provide information onshallow structures hosting mineralization and also a magnetic lineament with an unknown origin. Thesurvey, totally about 1.3 km long, was complemented by Radio MagnetoTelluric (RMT) measurements.Although an explosive source was used to generate the seismic signal, the seismic data show good qualityfor all the three components. Supported by the RMT results, clear reflections are observed in thehorizontal component data at about 25 m depth, one of them steeply dipping, likely associated with themagnetic lineament. Field static corrections were well estimated thanks to the close shot and receiverspacing and the broadband frequency content of the data. This study demonstrates that multicomponentseismic data can be useful for providing information on shallow structures and linking them to the surfacegeology. The vertical component data, however, show deeper penetration and better image the crystallinebasement and its undulated/faulted surface at about 50 m depth.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-286572 (URN)10.3997/2214-4609.20140509 (DOI)
Conference
76th EAGE Conference & Exhibition 2014, 16-19 June 2014 Amsterdam RAI, The Netherlands
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2018-06-04Bibliographically approved
Pedersen, L., Bastani, M., Dynesius, L. & Oskooi, B. (2001). Ground water exploration using high resolution RMT and CSTMT methods.
Open this publication in new window or tab >>Ground water exploration using high resolution RMT and CSTMT methods
2001 (English)Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:uu:diva-41039 (URN)
Available from: 2008-06-08 Created: 2008-06-08
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