PREDICTION OF OCCURRENCE AND HYDROGRAPH OF VOLCANIC DEBRIS FLOWS BY MONITORING GROUND TREMOR

Abstract

We have observed debris flows by using a new system of ground tremor sensors in the Nojiri River of Mt. Sakurajima, volcano, Japan. The purpose of this study is to obtain a reliable predicting method of debris flow in volcanic area which has less vegetation and therefore yields abundant sediment. To examine the phenomenon of debris flow, we carried out outdoor experiments of ground tremor, and replicated the surging out of debris in an active volcano. The frequency of ground tremor is approximately from 10 to 200 Hz. We were successful in finding the optimum value of parameters to estimate the hydrograph of debris flow by using a computer program of neural network. Our trigger system of detecting the debris flow is applicable to the occurrence of landslide, snow avalanche and so on.