Real-time Monitoring and Analysis of Debris Flow Events: Insight from seismic signal characteristics

Abstract. Debris flows triggered by rainfall are among the world’s most dangerous natural hazards due to their abrupt onset, rapid movement, and large boulder loads that can cause significant loss of life and infrastructure. Monitoring and early warning are key strategies for mitigating debris flows. However, deploying large instruments for continuous monitoring in challenging terrains like Wenchuan, China, is difficult due to complex topography and limited access to electricity and batteries. Recognizing the effectiveness of environmental seismology in monitoring geohazards, our study aims to establish a cost-effective, reliable, and practical debris flow monitoring system based on seismic monitoring in Wenchuan, China. We analyzed seismic signals and infrared images to determine debris flow characteristics and behavior. Through a case study in Fotangba Gully, we demonstrated how seismic signals can be used to track debris flow duration and confirm rainfall as the trigger. Using the cross-correlation function, we calculated the maximum velocity of the debris flow and validated it with the Manning formula. Our analysis of infrared imagery and power spectral density showed a strong correlation between debris flow seismic energy and its frequency spectrum, supporting the accuracy of using seismic signals to reconstruct debris flow events. This study provides a foundation for real-time monitoring, analysis, early warning, and hazard assessment in debris flow monitoring systems based on seismic signals.