Active structures and their relation to earthquakes along the eastern margin of the Japan Sea.

摘要

The distribution and characteristics of active faultsand folds along the eastern margin of the Japan Sea ere clarifiedmainly on the basis of seismic data of the Geological Survey ofJapan. The area was divided into the southern, middle andnortheastern parts according to their structural style. Thesouthern part is more than 100 km wide and 250 km longextending from Sado Island to the Oga Peninsula, where themajor faults tend to be concentrated in two fault zones. In themiddle part, a major fault zone forms the Okushiri Ridge whichextends from the west of the Nishitsugaru Basin to the west ofRumoi over a distance of 450 km, where the ridge consists ofseveral swells which are about 100 km in length.