Abstract
Seismic energies released from areas covered by 18 map sheets of 1: 200, 000 scale in Japan during the years 679-1990 and 1601-1990 are evaluated. They are denoted by E0 and E1, respectively. Meanwhile, the potential seismic energies Ef that could be expected from possible movement of active faults located in respective sheets are also evaluated. The seismic activities considered are mostly due to intraplate earthquakes as the locations of map sheets indicate.
As E1 is considerably larger than E0-E1 for most areas, it is highly likely that earthquake records in old days are missing. The relation between E1 and Ef indicates that the seismicity in the area where we have many active faults is high. On the assumption that overall earthquake occurrence or fault movement is governed by a Poisson process, the repeat time of fault movement is estimated as 500-2, 000 years on the average. There are a few areas for which we have Ef>>E0. It is suspected that a large earthquake might occur there in the future.
