Integration of Passive Seismic Techniques to Investigate the Landslide Dam Generated by the Yang Jia Gou Rock Avalanche (Sichuan–China)

Passive seismic techniques such as ambient noise recordings can be used to characterize landslide deposits. These techniques offer the advantage of being relatively inexpensive and expeditious, but pose interpretation difficulties due to a number of unknowns affecting the results of data inversion. The uncertainties can be reduced if some additional information about the subsoil conditions is obtained. We tested the integrated application of two different methods of ambient noise analysis to provide constraints for the subsurface reconstruction of the landslide dam made of the Yang Jia Gou rock avalanche deposit (Sichuan Province, China). In particular, we applied a cross correlation method, which can provide group velocity dispersion curves by exploiting the simultaneous synchronized recordings at different measurement stations. More reliable information on the structure and mechanical properties of the rock avalanche deposit was derived by combining the results of ambient noise analysis relying on a joint inversion of Rayleigh wave ellipticity and velocity. This allowed us to better constrain the modelling results, improving the resolution of the landslide dam internal structure and its overall thickness. The bedrock consisting of slates with Vs velocity > 1000 m/s, locally appears to coincide with the base level of the Yang Jia gully torrent, which breached the landslide dam.