Structures of the Xishancun Landslide inferred from joint inversion of Rayleigh wave ZH ratio and Love wave group velocity

Rayleigh wave ellipticity (or ZH Ratio) is frequency-dependent and sensitive to shallow crustal structures beneath the seismograph station. Because the depth sensitivity kernels of ZH ratio differ from those of dispersion data， the ZH ratio offers valuable complementary information for dispersion-based inversion methods. Consequently， combining the ZH ratio with dispersion data allows for obtaining improved subsurface velocity structures. In this study， we used a joint inversion method that integrates Rayleigh wave ZH ratio and Love wave dispersion data using a Neighborhood Algorithm (NA) to obtain shallow structures of the Xishancun landslide in Li County， Sichuan Province， southwest China. Synthetic tests indicates that the joint inversion technique yields a more reliable and precise model of shallow subsurface shear-wave velocity (Vs) and Vp/Vs for layered media. The results indicate Vs of the landslide body layer ranges from 0.3 to 0.7 km/s， while Vs 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.