抄録
Focal machanisms are determined for about 300 shocks, which occurred in the Kanto-Tokai District during the period 1979 through 1983. First-motion data are taken from Japan Meteorological Agency, National Research Center for Disaster Prevention, Earthquake Research Institute (7 stations) and Abuyama Seismological Observatory.
In the Northern Kanto District, low-angle thrust fault type solution is predominant for earthquakes shallower than about 70km. Most of these belong to the upper seismic plane. Earthquake in the lower seismic plane are characterized by down dip tension and those in the upper seismic plane by down dip compression but with various azimuths.
In the Southern Kanto District, earthquakes of reverse type with E-W compression and of normal type with E-W extension are considered to be related to the subduction of the Pacific plate, and those of reverse type with N-S compression and of strike slip type with N-S compression are supposed to be related to the subduction of the Philippins Sea plate. In and around the Izu Peninsula, tension axes are systematically distributed so as to make coaxial circles whose center is at a point in the north of Suruga Bay.
In the Tokai district, the upper crustal earthquakes are predominantly of strike slip type with E-W to SE-NW compression, whereas the subcrustal earthquakes are of strike slip or of normal faulting with E-W extension.
