56 / 2021-11-15 19:33:08

Dynamic processes of the 2021 “4.5” Hongya rock avalanche revealed by seismic signals

Rock avalanche, Seismic signal, Dynamic processes, Field monitoring data

The catastrophic 2021 “4.5” Hongya rock avalanche in Sichuan, China occurred early on the morning of April 5, 2021. The seismic signals generated by the avalanche were recorded by 10 seismic stations around the avalanche site. In this study, the spectrogram of the vertical component of the seismic signals recorded by the E Mei Shan (EMS) seismic station, the closest station to the avalanche, was calculated. Then, combined with the dominant frequency band of the vertical component of the seismic signals recorded by the EMS station and field investigation, the dynamic processes of the avalanche were divided into four stages: collapsing, triggering, scraping, and depositing. It was found that high and steep terrain, the existence of thick and soft interlayers, and the development of joints and fissures provided the conditions for the occurrence of the avalanche. Additionally, the infiltration and evaporation cycle of rain water reduced the stability and intensified the fragmentation of the rock mass. The field monitoring data indicate that the source and deposition zones are still deforming and, according to the local climate conditions, the deposition body has the possibility of transforming to debris flow under the action of heavy and continuous rainfall. This study demonstrates that seismic signals can provide an effective method for analyzing the dynamic processes of rock avalanches.