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3C seismic landstreamer study of an esker architecture through shear- and surface-wave imaging
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.ORCID iD: 0000-0003-4694-9847
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.ORCID iD: 0000-0003-1241-2988
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

As a continuation of a seismic experiment to test the capability of a newly developed 3C(three component) MEMS-based (microelectro-mechanical system) seismic landstreamer fordelineating an esker core (porous glacial sediments), depth to water table and bedrock insouthwestern Finland, additional analysis of the same dataset was performed. The seismic sourceused was a 500-kg vertical impact drophammer. We report results from one of the horizontalcomponents of the landstreamer data, the transverse (SH-wave) component. In addition to this,we complement the interpretation conducted previously on P-wave stacked section with surfacewavederived shear-wave velocities and Vp/Vs ratios along the entire profile.Although the seismic source used is of vertical-type nature, peculiarly, the data inspectionshowed clear bedrock reflection on the SH-wave component. This observation led us toscrutinize the transverse component data through side-by-side inspection of the shot records onall the three components and particle motion (hodograms) analysis to confirm the pure shearnature of the reflection. Using the apparent moveout velocity of the reflection, as well as knowndepth to bedrock based on drilling, we employed finite-difference synthetic modelling to furtherverify the nature of the reflection. Compared to the P-wave seismic section, bedrock is moreaccurately delineated on the SH-wave section. Some structures connected to the MUKH(morphologically undetectable kettle hole) imaged on the P-wave results are also notable on theSH-wave section, and particularly on the surface-wave derived shear-wave velocity model. Ourresults indicate that the SH-wave energy is generated at the source location itself. This study isencouraging and illustrates why multicomponent seismic data should be acquired and analyzedfor near-surface applications.

Keywords [en]
landstreamer, shear-waves, surface-waves, MASW
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
URN: urn:nbn:se:uu:diva-335429OAI: oai:DiVA.org:uu-335429DiVA, id: diva2:1162751
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-10
In thesis
1. Three-component digital-based seismic landstreamer: Methodologies for infrastructure planning applications
Open this publication in new window or tab >>Three-component digital-based seismic landstreamer: Methodologies for infrastructure planning applications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To support urban infrastructure planning projects, along with various other near-surface applications, a multicomponent landstreamer was developed. The landstreamer was built with broadband (0-800 Hz), three-component (3C) micro-electro-mechanical system (MEMS) sensors. The digital nature of the MEMS sensors makes the developed landstreamer insensitive to electric/electromagnetic noise.

The landstreamer’s design and its seismic imaging capabilities, along with the MEMS technical specifications, were evaluated in several studies. When comparing signals recorded with the streamer with planted MEMS sensors, no negative effects of the design were noted. Compared to different geophones tested, the streamer produced higher quality and broader signal bandwidth data. Additionally, a seismic study conducted in a tunnel demonstrated its electric/electromagnetic noise insensitivity. The streamer combined with wireless seismic recorders was used to survey logistically challenging areas for improved imaging and characterizations and avoid interference with traffic.

For example, at the Stockholm Bypass site, the landstreamer recorded data were used for traveltime tomography with results showing a well delineated bedrock level and potential low-velocity zones matching with inferred poor-quality-class rocks. The seismic response of fractures and their extent between a tunnel and the surface was studied at the Äspö Hard Rock Laboratory site. The velocity model obtained using the traveltime tomography approach showed known well-characterized fracture systems and potential additional formerly unknown ones. Additionally, compressional- and shear-wave velocities, seismic quality factors, Vp/Vs and dynamic Poisson’s ratios of the known fracture zones were obtained. Fractures and/or weakness zones in the bedrock were imaged using refraction and reflection imaging methods at a site contaminated with a cancerogenic pollutant in southwest Sweden, illustrating the potential of the streamer for environmental-related applications. In southern Finland, the landstreamer was used for SH-wave reflection seismic imaging from a vertically oriented impact source with the results showing a well-delineated bedrock level and weak reflections correlating well with geology. At the same site, its potential for multichannel analysis of surface waves (MASW) was demonstrated. The surface-wave obtained shear-wave velocities match well with the borehole based stratigraphy of the site and are complementary to the SH-wave reflectivity and previous investigations at the site.

Studies conducted in this thesis demonstrate the landstreamer’s potential for various near-surface applications and show the benefits and need for 3C seismic data recording. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 80
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1610
Keywords
landstreamer, multicomponent seismic, shear-waves, surface-waves
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-335846 (URN)978-91-513-0186-0 (ISBN)
Public defence
2018-02-02, Hambergsalen, Geocentrum, Villavagen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2018-01-10 Created: 2017-12-10 Last updated: 2018-03-07

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Citation style
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