「200万分の1日本列島活断層図」
過去数十万年間の断層活動の特徴
2000 年 2000 巻 19 号 p. 3-12
詳細
2000 年 2000 巻 19 号 p. 3-12
We compiled a totally new 1: 2,000,000 active faults map of Japan based on the digitized GIS data of active faults in the scale of 1: 25,000 by Active Faults Map Working Group (1999).
The new map differs from the existing active faults maps of Japan in t wo points. One is the definition of active faults and the other the scale of base maps. We defined active faults as faults that have repeatedly moved during the late Quaternary with intervals of one thousand to ten thousand years forming distinctive fault-related tectonic features on the earth surface. The Research Group for Active Fault Studies (1980,1991) and other previous studies commonly defined active faults as faults that repeatedly moved during Quaternary and are the potential sources for future earthquakes. Therefore, our criterion is stricter for recognition of active faults than those used for the previous mapping. The other difference is accuracy in mapping of active faults; our map is based on the active faults map data in scale of 1: 25,000 while others mostly based on much smaller scale data. Through our mapping, some faults previously recognized as active because of existence of Quaternary faults were not treated as active if these faults are not associated with fault-related tectonic features on the ground. On the other hand, many faults are newly found as active by our detailed photo-interpretation.
We assembled active faults about 140 fault groups based on the f ollowing criteria; 1. Faults more than 10km long in dimension,2. Isolated from the neighboring faults at least 5 km apart, and similar type of faulting, strike and sense of faulting. We compared the active faults map with geoloic map to know their characteristic occurrence of faults. We prepared maps for type, activity, and density of faulting to know the regional characteristic of active faulting in Japan. We also examined the possibility of occurrence of new active faults and expansion of faults based on the mode of cumulative slips distribution along their traces.
