关键词: 日本海, 中国东北, 震源深度, 应力状态, 贝尼奥夫带

Abstract: The distributions of earthquakes in the Japan Sea and the Northeast China were studied using the hypocenters determined by I. S. C. from 1966 to 1981. It is shown that the Benioff zone from the northern Honshu to the Northeast China, which is perpendicular to offshore trench of Japan is continuous, dipping about N85°W with a dip angle of about 29° and a thickness of 20 km, extending down to a depths no more than 560 km. The mechanismsn of earthquakes of M_b≥5.0 in the region between the northern Honshu of Japan and the Northeast China were also studied. It is shown that the stress field in the Northeast China coincides with that in the Japan Sea, suggesting that the stress field is caused by compression of pacific plate. In the Benioff zone the directions of the axes of compressional stress vary with the depth: In the region of depth from 100km to 200km the stress state is not simple; most P axes are coincident with the direction and dip angle of the Benioff zone; a few P axes are in the plane of subduction and some of T axes are close to the direction of subduction; in the region of depth from 200 km to 500 km. the most of P axes are nearly horizontal and perpendicular to the strike direction of the Benioff zone; in the depth below 500 km, the P axes are coincident with dip deriction and dip argle of the Benioff zone.

Key words: Japan Sea, Northeast China, Focal depth, Stress state, Benioff zone