3:30 PM - 3:45 PM
[SSS07-13] Structures of the Xishancun Landslide inferred from ambient seismic noises
★Invited Papers
Seismic velocity structures provide important information for estimating landslide volume, constructing three-dimensional geological models, and identifying weak positions of sliding surfaces. This information is essential for assessing slope stability, predicting failure probability, and facilitates the development of early warning systems, prevention engineering design, as well as post-disaster emergency response planning. Toward this end, a temporary seismic array consisting of 59 broadband and short-period seismometers was deployed in the Xishancun Landslide in Li County, China, with a spacing interval of about 200 m. We use several methods based on ambient seismic noises, including surface wave tomography, autocorrelation, horizontal-to-vertical spectral ratio, to investigate shear-wave velocity structures of the landslide. We also use joint inversion of Rayleigh wave ellipticity from slidequakes observed in the landslide and Love wave group velocities for this purpose. The results indicate the thickness of the Xishancun landslide is 57-102 m. These values generally agree with the thicknesses from borehole data. However, some stations show very large discrepancies, probably because of strong lateral heterogeneity. Shear velocity of the landslide ranges from 0.3 to 0.7 km/s, while shear velocity of the bedrock varies from 0.7 to 1.1 km/s. In the southern part of the landslide, a low-velocity layer exists at depths of 40~80 m, with a thickness of approximately 10~20 m. This finding suggests that the majority of the southern region of the landslide is characterized by loose material accumulation and groundwater enrichment, which contributes to a decrease in shear strength.