SEISMIC ACTIVITIES AND CRUSTAL MOVEMENTS AT THE YAMASAKI FAULT AND SURROUNDING REGIONS IN THE SOUTHWEST JAPAN

Abstract

Data from the continuous observation of microearthquakes which occur along the Yamasaki Fault and in the surrounding regions have been analyzed. There are some active lines of alignment of microearthquakes. Each of these corresponds to an active fault. We can find some properties of the block structure and the block movements of the crust from the temporal variation of the activity. The fractured zone of the Yamasaki Fault shows some characteristic behaviors of strain change related to the activity of microearthquakes. These phenomena are closely related to the change of water level of the river along the fault and rainfalls at the concerned region. Heavy rainfalls often triggers the occurrence of shallow earthquakes along the faults. Such characteristics are very useful for the earthquake prediction in very short time range.