降雨に対する地殻歪レスポンスの異常と地震発生
1981 年 34 巻 3 号 p. 301-310
詳細
1981 年 34 巻 3 号 p. 301-310
Precursory abnormal strain responses associated with rainfall are discussed in the present paper. The data analized are the strains observed at the Mikawa Crustal Movement Observatory (Toyohashi City, central Japan) for the period from January 1973 to April 1980. Each extensometer at the observatory is equipped with two or three sensors for the detection of irregularity in strain. Usually the observation gallery deforms uniformly after a rainfall, because the ground strain responses observed by the sensors attached on the same quartz pipe show nearly the same variation. We can calculate accurately these strain responses by a tank model from the precipitation at the observatory, but sometimes remarkable disagreements between the ground strains caused by rainfalls and the calculated values expected from the model are clearly seen before and after the occurrence of nearby earthquakes. Irregular deformations at the observation site are also observed. These abnormal strain responses to rainfall are observed for 18 earthquakes during the period from January 1973 to December 1979. Distribution of earthquakes which were accompanied by these precursory abnormal strain responses are restricted in the block whose boundary is characterized by the distribution of microearthquakes.
