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

Abstract

Quick-clay landslides are important geohazards in Sweden, Norway, and Canada. While they have been studied using various geotechnical and geophysical methods, only a handful of seismic surveys have been reported for their studies. Here, we reprocess active-source seismic data from a quick-clay landslide site in southwest Sweden, to complement earlier studies of reflection imaging and first-break traveltime tomography with surface-wave dispersion analysis. Results suggest extremely low shear-wave velocities, even as low as 60-100 m/s. From a geotechnical perspective, this implies that the region classifies as a high-risk zone for landslides and construction purposes. High or anomalous values of Poisson's ratio (or similarly P-and S-wave velocity ratio) depicts a zone within the normally consolidated sediments that likely represents a coarse-grained layer, thus confirming earlier results from a number of boreholes drilled in the study area. Overall, the results present further support to the previous This article is protected by copyright. All rights reserved.2 hypothesis that the coarse-grained layer plays a major role in the formation and creation of quick-clay landslides in the study area. Additionally, an attempt to model the distribution of potential quick clays along one of the seismic profiles is performed by combination of the modelled geophysical properties and soil textures. This study illustrates the potential of seismic methods, and how integration of multiple geophysical properties and different data handling strategies can help to accurately characterise regions susceptible to quick-clay landslides.

High‐resolution P‐ and S‐wavefield seismic investigations of a quick‐clay site in southwest of Sweden

“…As confirmed by the V P model shown in Figure 5a and similar to P1, the thickness of the sediments increases in this lowland area. Compared to P1, the estimated V S (Figure 5b) is slightly higher (100-200 m/s) and estimated V P /V S lower (5-15) (Figure 5c), but within the ranges expected for saturated clay sediments and conditions of high water content (e.g., Donohue et al, 2012;Salas-Romero et al, 2021). Considering the sudden change in the bedrock morphology and thickening of the sediments at the slope of P2, as well as the severe topography change, this region is probably at high risk of failure.…”

Low Vp/Vs Values as an Indicator for Fractures in the Critical Zone

“…There are observations of V p /V s values that fall within V p /V s of 1.6–1.8, but they seem to be the exception (Liberty et al., 2022; Uhlemann et al., 2016). Other observations report a larger‐than‐expected range, including high V p /V s values greater than 4 (Flinchum et al., 2020; Pasquet et al., 2015a; Stümpel et al., 1984) or even as high as 20 (Salas‐Romero et al., 2021). There are reports of V p /V s values less than 1.4 in the CZ of Brazil (Trichandi et al., 2022), in dry soils (Salem, 2015), and in full waveform inversion results in the CZ of Pennsylvania (Liu et al., 2022).…”

A Developed Shear Wave Source for Shallow Seismic Survey

“…The propagation velocities of body waves are a function of the elastic properties of the soil layer, especially Vs is a key parameter to compute the stiffness of materials [23]. Once the Vs is known, the shear modulus () of soil or rock can be estimated as related by Eq.…”

“…However, it is not worth using this instrument for shallow seismic survey because of its heavy weight and the need pre-signal decoder [19]. In the past decades, the Vs obtained from Multichannel Analysis of Surface Waves (MASW) is increasingly used [20][21][22][23]. This method uses surface wave energy, released from the P-wave source to calculate the Vs.…”