关键词: 郯庐断裂带北段, 震源机制解, 地壳应力, 西太平洋板块, 中国东北

Abstract: 1254 M_L≥2.0 earthquakes from Jan.1964 to Jan.2008,191 focal mechanism solutions and 198 in-situ stress measurement data in the northern Tanlu Fault zone and its adjacent areas are collected to analyze the seismic activity,structural stress state and fault movement of the northern Tanlu Fault zone through the calculation of epicenter distribution,focal depth,strain release rate and the statistics of focal mechanism solutions and other stress data.The results indicate that the study area can be partitioned into four seismic belts or regions,namely the Sea of Japan to Changbai Mountains deep seismic belt,the northern Tanlu Fault seismic belt,the western margin of Songliao basin seismic belt and the inner Songliao basin seismic belt.The seismic activity of the northern Tanlu Fault zone is weak and inhomogeneous.The Yilan-Yitong Fault is more active than the Dunhua-Mishan Fault,and shows segmentation behavior that is stronger at both sides than the middle part.The maximal stress axis(P-axis) in the deep seismic belt trends 288° on average,dipping 31° and the main fault movement mode is reverse.Near the northern Tanlu Fault zone the P-axis mainly trends NEE-SWW,dipping 26° on average,the T-axis mainly trends NNW-SSE,dipping 23° on average and the main fault movement mode is strike-slip with reverse.The maximal stress axis presents an obvious difference between the shallow and deep earthquake belts,resulting probably from the influence of the secondary stress field derived from the dextral strike-slip of the northern Tanlu Fault zone under the NWW compression due to the low-angle high-speed subduction of the western Pacific plate.

Key words: northern Tanlu Fault zone, focal mechanism solution, stress state, western Pacific plate, northeast China