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Multi-component digital-based seismic landstreamer and boat-towed radio-magnetotelluric acquisition systems for improved subsurface characterization in the urban environment
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
Geological Survey of Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
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2017 (English)In: First Break, ISSN 0263-5046, E-ISSN 1365-2397, Vol. 35, no 8, p. 41-47Article in journal (Other academic) Published
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).

Place, publisher, year, edition, pages
Amsterdam, Netherlands, 2017. Vol. 35, no 8, p. 41-47
National Category
Geophysics
Identifiers
URN: urn:nbn:se:uu:diva-327951OAI: oai:DiVA.org:uu-327951DiVA, id: diva2:1131287
Projects
TRUST GeoinfraAvailable from: 2017-08-14 Created: 2017-08-14 Last updated: 2017-12-10Bibliographically approved
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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Brodic, BojanMalehmir, AlirezaMehta, SumanJuhlin, ChristopherLundberg, EmilWang, Shunguo

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