Regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995

The time and spatial feature of the regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17,1995, was studied. The concerned region is about several hundred kilometers in length and breadth surrounding the epicenter (33°-37°N, 133°-138°E). It is divided into 16 subregions. The seismicity of these subregions from January of 1976 to June of 1996 has been analyzed. It is showed that, 1 there were significant seismicity changes in 10 subregions triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995. These changes passed a Z statistic test exceeding 0.95 confidence level and the greatest epicenter distance of these subregions was 280 km; 2 seismicity changes were triggered within 1-5 days in three subregions near the main shock while in other subregions the seismicity changes were triggered within several ten days after the main shock; 3 the greatest triggered event is 5.4, which is about the same size as the greatest aftershock; 4 the regional stress change resulted from the main shock may be the triggered mechanism of the regional seismicity.[PUBLICATION ABSTRACT]