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

摘要： 本文分析了日本海及中国东北的地震深度分布。证实了日本本州北部至中国东北的贝尼奥夫带(Benioff)基本是连续的,该带的倾向约为北85°西,倾角约为29°,深度在150公里以下贝尼奥夫带厚度约为20公里。研究了日本本州北部至中国东北的震级M_b≥5.0地震的震源机制解,发现中国东北地壳应力场与日本海地壳的应力场方向一致,来源于太平洋板块的挤压。在俯冲带上,深度在100公里到200公里之间的情况较为复杂,大多数地震显示的主压应力方向与贝尼奥夫带的倾向、倾角一致,有的T轴取向与贝尼奥夫带的倾向、倾角一致,有的特征方向与贝尼奥夫带倾向、倾角均不一致。深度在200公里至500公里之间,主压应力方向近于水平,并与贝尼奥夫带走向垂直,张应力轴相对集中。深度大于500公里时,主压应力方向与贝尼奥夫带的倾向、倾角一致,张应力轴相对集中。

关键词: 日本海, 中国东北, 震源深度, 应力状态, 贝尼奥夫带