Full text loading...
-
The forgotten shear-wave reflections in the compressional-wave surveys
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, NSG2021 27th European Meeting of Environmental and Engineering Geophysics, Aug 2021, Volume 2021, p.1 - 5
Abstract
It is impossible to acquire a land seismic dataset that contains purely compressional (P-wave) or purely shear (S-wave) information. Different wave modes usually leak from one to another although may be dominant in one wave mode depending on the instrumentation and setup used. Following an earlier study, in this work I show a reasonable amount of shear-wave reflections can be extracted from typical the so-called P-wave type surveys. This was possible thanks to the extreme slow background shear-wave velocity (85–90 m/s) in the study area allowing a good separation of P- from S-wave reflections. It is important that this possibility is recognized and methods are developed to extract these reflections at the same time and when designing a seismic survey. The minimum is to make sure shear-waves in such an extremely slow-velocity setting are not aliased and properly sampled. The study site, in southwest Sweden, hosts quick clays hence the additional information is significant geotechnically and the added value is great for studying the safety condition of the site. It also implies that the water content is quite high (Vp/Vs=15), a by-product conclusion concerning the liquefaction potential of the site if a landslide is triggered.