Abstract
The Japanese on-land seismogenic faults are listed with historical shallow earthquakes of greater than M 5.0, based on‘Active Faults in Japan’published by the Research Group for Active Faults of Japan, in 1991. Total numbers of listed seismogenic faults (defined by Matsuda,1990) and earthquakes over the Japanese Islands are 263 and 449, respectively.
The numbers of faultsper 10,000km2 in Japan on land are about 7 on an average. The numbers are the largest in the Chubu (21) and Kinki (17) districts and the smallest in Hokkaido (3). About a half of the seismogenic faults are shorter than 20km in length. Faults longer than 80km are only 9 in number (3%). Faults with strike-slip component in the displacement are very common in western Japan, while faults with no strikeslip component, mostly reverse faults, are dominant (more than 90% in the areas) in Hokkaido and Tohoku districts.
The known historical shallow on-land earthquakes larger than M5.0 in the period from AD1600 to 1999, are 420 in number, which are more than 90% of the total known since AD600. In 1900's, the earthquake of M>7,7>M>6,6>M>5 are 13,83,134 in number, respectively. The number of M>5 earthquakes per 10,000km2is the largest in Chubu district (10/10,000km2), followed by Kyushu-Ryukyu and Kanto districts. The successive earthquakes of M>5 in one year and less than 15km apart from each other have occurred mostly on the back arc side of volcanic fronts on the Islands. The half of the successive earthquakes relates in distribution to volcanic areas rather than known seimogenic faults.
There is a close relationship between distr i b utions of seismogenic faults and of historical earthquakes of M>5: the Chubu district is the highest in distribution density both of faults and earthquakes. The most (abou t 80%) of earthquakes of M>7 have been occurred in areas within 15km in distance from seismogenic faults.
