Research on the seismic signal characteristics of debris flow: an in-field monitoring approach

Debris flow hazard often brings huge economic losses and fatalities downstream. Despite the traditional in-field monitoring system developed, the apparatus is vulnerable to being damaged in the process of hazards, resulting in limited in-situ data collected to analyze the dynamic process. Recently, with the development of seismology, the seismic signals from geophones become an effective method to analyze the process of debris flow for hazard assessment. The scientific challenge lies in how to get the seismic signals of the whole process of debris flow accurately for analyzing the seismic signal characteristics and of debris flow. In this study, two debris flow gullies (Er gully and Chediguan gully in Wenchuan county) are selected to install the monitoring apparatus after field investigation, and two monitoring sites are selected for each gully. The ground vibration monitoring system consists of geophone and Data-Cube. The geophone is fixed in the concrete base which is clinging to the bedrock firmly to collect the seismic signals and save the seismic signals in the Data-Cube. In addition, each monitoring site is equipped with an infrared camera for recording the geomorphologic changes of the monitoring section in the gully, and a rain gauge is installed at the monitoring site upstream of each gully to obtain rainfall information during the whole observation period. The ambient noise in raw seismic signals will be filtered out, and the filter seismic signals are combined with rainfall information to analyze the moment of potential hazards. Then identify debris flow by checking the video of the infrared camera and analyzing the spectrum, spectrogram, and power spectra density of these potential hazards. Finally, the seismic signal characteristics of the debris flow are extracted and analyzed. Based on this, the monitoring and early warning work of debris flow hazards can be guided.