Integration of SH seismic reflection and Love-wave dispersion data for shear wave velocity determination over quick clays

Abstract

Quick clay is a water-saturated formation originally formed through flocculation and deposition in a marine to brackish environment. It is subsequently leached to low salinity by freshwater flow. If its strength decreases, then the flocculated structure collapses leading to landslides of varying destructiveness. Leaching can result in a reduction of the undisturbed shear strength of these clays and suggestions exist that a reduction in shear wave velocities is also possible. Integration of SH seismic reflection and Love-wave dispersion data was undertaken, in an area near the Göta River in southwest Sweden, to evaluate the potential of shear wave velocity imaging for detecting quick clays. Seismic reflection processing evidenced several geologically interesting interfaces related to the probable presence of quick clays (locally confirmed by boreholes) and sand-gravelly layers strongly contributing to water circulation within them. Dispersion data were extracted with a Gaussian windowing approach and inverted with a laterally constrained inversion using a priori information from the seismic reflection imaging. The inversion of dispersion curves has evidenced the presence of a low velocity layer (lvl, with a velocity reduction of ca. 30 per cent) probably associable to quick clays. This velocity reduction is enough to produce detectable phase-velocity differences in the field data and to achieve a better velocity resolution if compared to reflection seismic velocity analyses. The proposed approach has the potential of a comprehensive determination of the shear wave velocity distribution in the shallow subsurface. A sensitivity analysis of Love-wave dispersion data is also presented underlining that, despite limited dispersion of the data set and the velocity-reducing effect of quick-clay leaching, the proposed interpretation procedure arises as a valuable approach in quick clay and other lvl identification.

Geotechnical site characterization using multichannel analysis of surface waves: A case study of an area prone to quick‐clay landslides in southwest Sweden

“…However, the VP/VS values are extremely high in the edges of the profile with values above 20, which seem unrealistic and not representative for saturated clays and sands. The high values of VP/VS in these positions may be related to a lower resolution of the VS and VP models in these areas and/or due to extremely low VS (studies in the same area,Polom et al 2013 andComina et al 2017, obtained similar values) Bailey et al (2013). associate high VP/VS to an increased porosity, saturation and clay content, all of which are conditions present in this study area.…”

“…They have extensively been studied by geotechnical and resistivity methods (Dahlin et al 2013;Löfroth et al 2011;Lundström, Larsson and Dahlin 2009;Solberg et al 2012Solberg et al , 2016Wang, Malehmir and Bastani 2016), while only a few studies report the usage of surface-wave dispersion analysis for different investigations on quick clays (e.g. Comina et al 2017;Donohue et al 2012;Long, Wood and L'Heureux 2017;Sauvin et al 2013). Some of the most recent works on quick clays (leached clays) revealed that these materials cannot be distinguished from unleached clays using only shear-wave velocity (VS) measurements (Long et al 2017).…”

“…This area has been subjected to numerous geophysical, geotechnical and hydrological surveys (Fig. 1, Adamczyk et al 2013Adamczyk et al , 2014Comina et al 2017;Dahlin et al 2013;Malehmir et al 2013a, b;Löfroth et al 2011;Lundberg et al 2014;Polom et al 2013;Salas-Romero et al 2016, 2019Shan et al 2014Shan et al , 2016Wang et al 2016). The main target of these different investigations was mostly quick-clay mapping.…”

SH Seismoelectric Response of a Glacier: An Analytic Study

“…With the objective of contributing to characterize and understand the seismoelectric method when applied to glacial environments, we present in this work an analytic study of the electromagnetic responses to pure shear horizontal (SH) seismic waves, generated by a shearing force acting at the top of a glacier overlying a rocky substratum. Concerning the choice of the source, on the one hand, we have proved in a previous work (Zyserman et al, 2017a) that the signal-to-noise ratio can be higher in this case than when using compressional sources, and on the other hand, although up to now this kind of sources has not been used in seismoelectric field studies, they have been employed successfully in several works aiming to characterize the shallow subsurface (Beilecke et al, 2016;Comina et al, 2017;Konstantaki et al, 2013;Konstantaki et al, 2015;Prior et al, 2017;Stucchi et al, 2017). The ice forming the glacier is treated as an elastic medium; this is a common assumption when performing seismic studies (Collins et al, 2016;Podolskiy & Fabian, 2016;Presnov et al, 2014b;Presnov et al, 2014a).…”

An analytical solution to assess theSHseismoelectric response of the vadose zone

“…Quite recently, Beilecke et al (2016) carried out high resolution, near surface, shear wave reflection seismic measurements to investigate the fault structure in a CO 2 deposition site in Australia. We mention, finally, the works of Stucchi et al (2017) and Comina et al (2017), integrating SH-wave measurements with P wave and Love-wave, respectively, to investigate different geological systems to assess landslide risks. The mentioned works show that there is evidence of successful usage of SH waves to investigate the subsoil.…”