降雨と地震発生との関係について

Abstract

Some characteristic evidences suggesting that the heavy rainfall triggers the occurrence ofearthquakes are described as follows;(a) Monthly distribution of frequency of shallow shocks in the Inner Zone of the SouthwestJapan shows the similar pattern as the rates of change of mean monthly precipita-tion.(b) Many large earthquakes occur at the beginnings of the rainy seasons.? In many cases local heavy rainfalls take place in the epicentral region in a few daysbefore the occurrence of earthquakes.(d) There are many cases in which earthquakes occur 3 to 5 days after heavy rainfalls(e) Microearthquake activity along the Yamasaki Fault clearly increases when large effectof rainfall is observed by extensometers crossing the fractured zone.(f) Temporal variation of microearthquake activity along the active fault corresponds wellto the variation of precipitation and the water level of the river.