Calibration of infrasound monitoring system and acoustic characteristics of debris-flow movement by field studies

摘要

Naturally occurring infrasounds produced by debris flows are explored in this study by examining the field data both in Jiangjia Gully, Yunnan and Houyenshan, Taiwan, respectively. Infrasound propagates to long distance in the atmosphere at the speed of sound for the low adsorption in the air and the high reflectivity of the ground. The infrasonic signals induced by debris flows are related to the magnitude and composition of the failure zone as well as the slope areas. In Jiangjia Gullies, the peak frequency of infrasounds is about 6 Hz when debris flow discharges are less than 500 m3/s. While the peak frequency decreases with the increasing discharge of debris flows. The stony debris flows occur in Houyenshan with the peak frequencies between 5-15 Hz during the surges. Non-stationary acoustic signals of the debris flows are analyzed by adopting the HHT approach.