地震前兆現象の事例研究

抄録

Pattern of occurrence of precursory phenomena differs significantly in various respects for each earthquake. It is not the same even for earthquakes occurring in adjacent areas. Amplitude of precursory change is not necessarily large at nearer sites, and that it is very often larger than that of coseismic change. These features suggest that precursors occur locally at weak points or stress concentrating sites. It seems that desrimination of earthquake precursors from noises which are not directly related to the occurrence of earthquake is intrinsically difficult. Whether some observed change is a precursor or not may be expressed in a probabilistic way. When various kinds of anomalous change are observed at the same time, the possibility that they are true precursors will be increased. It is important to elucidate the occurrence mechanism of precursors in relation with structure and its change of seismogenic field.