Advances in Seismic Imaging of Quick Clays in Sweden

Quick clays are special types of soils that can liquefy under excess pore-water pressure with relatively low intrinsic stresses, resulting in landslides. In an area prone to quick-clay landslides in Sweden, various geophysical methods have been performed to map the subsurface. However, due to the high conductivity of the near-surface materials, seismic methods have shown greater potential than other geophysical methods. To exemplify this, a 2D seismic profile is presented with a 1 m shot and receiver spacing, having the highest resolution data so far acquired at the site. A processing workflow is followed to obtain P- and S- wave sections and their velocity models. Three main reflections identified early from raw shot gathers, are imaged in the final seismic sections. Borehole logging data are used to correlate the deepest reflection with the bedrock, overlayed by two coarse-grained layers. Our findings show the site is characterised by extremely slow S-wave velocities, between 60–100 m/s, that are indicative of high-water content along with the presence of quick-clay materials suggesting that the site requires special attention for future risk mitigation of landslides.