Distribution and failure mechanism of landslides associated with seismic response of the slope during the 2022 Lushan Ms6.1 earthquake

In recent years, the frequent occurrence of intense seismic events in the mountainous regions of western China has led to numerous geological disasters, resulting in significant human casualties and extensive property damage. Understanding the seismic response of slopes is crucial for elucidating the failure mechanism of earthquake-induced landslides. The distribution of geological landslides and the seismic response of slopes in Lushan are examined through post-earthquake field investigations, landslides inventories, and comprehensive field monitoring. The landslides triggered by the earthquake were primarily concentrated along both banks of the Donghe River in Baoxing County, predominantly manifesting as rockfalls. Geological disasters are predominantly occurred along fault zones and water systems, where vulnerabilities are heightened near 1 km of these faults. The topographic features, lithological composition, and rock mass structure significantly influences the Peak Ground Acceleration (PGA). Notably, PGA experience a sudden increase in areas with slope breaks and loose soil layers, leading to initiation location of the landslide. In the monitoring profile, the PGA amplification factors increases significantly along the slope surface: PGA at the upper slope is 1 to 2 times greater than that of the hilltop reference point, and within the loose soil layer, it ranges from 1.5 to 3.0. Seismic waves in the 1–5 Hz frequency range are notably amplified in this profile, as evidenced by analysis of the Fourier spectrum and Horizontal to Vertical Spectral Ratio (HVSR) curve. The monitoring profile data reveals that site conditions have a pronounced influence on the amplitude of the acceleration, surpassing the magnification effects of terrain and elevation. In disaster investigations, deviations in the development of disasters from the epicentral area are observed, especially in regions with complex geological structures like nappe tectonics. In such cases, it is crucial to emphasize the impact of both the macroscopic and microscopic epicentershaode. Additionally, more attentions should be paid to understanding the seismic response of slopes, particularly concerning earthquake-triggered landslides.