Extracting the source characteristics of the April 2022 Guanyuan landslide event from seismic signals recorded in the near-field

The seismic signature of landslides preserves information of utmost importance in reconstructing the impact forces induced by landslides and, subsequently, the trajectory of motion and the dynamic properties of the sliding mass. Several studies focusing on large-scale events successfully inverted the source-time function and, therefore, the time-varying force exerted on the surface from the observed low-frequency (<0.1 Hz) seismic waves recorded in the far field. Nonetheless, most landslide events are small in terms of the displaced mass, which is more likely to excite rapidly attenuating seismic waves. With dominant frequencies above 1 Hz, these waves are noticeable only at the stations near the landslide. Analyzing the seismic signal generated by landslides in the near field is challenging. The proposed models would require a thorough description of the ground propagation medium, which is only available for some study cases. Here, we investigate using analytical solutions to Lamb’s problem to simulate the propagation history of the surface waves during the April 2022 Guanyuan landslide, Taiwan. This landslide mobilised more than 100,000 m³ of rock and stopped the traffic on the Taiwanese Central Cross-Island Highway for 43 days. The proximity of the landslide to a broadband station located about 6 km away allows the study of the near-field seismic signals. The duration and amplitude of the force retrieved in this fashion agree with qualitative observations, suggesting the potential of the model to extract source characteristics of landslides from seismic signals recorded in the near field.