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

摘要： 收集了郯庐断裂带北段及邻区自1964年1月至2008年1月的1254个ML≥2.0的地震数据和191条震源机制解、198条原地应力测量数据,通过震中分布、震源深度、应变释放速率的分析计算和震源机制解及其它应力数据的统计,探讨了郯庐北段现今的地震活动性和应力状态。结果表明,郯庐断裂带北段及邻区的地震活动可分为日本海-长白山深震区、郯庐断裂带北段地震区、松辽盆地西缘地震区和松辽盆地内部地震区;郯庐断裂带北段现今地震强度较小,频度较低,但空间差异性显著,依兰-伊通断裂活动性比敦化-密山断裂强,且具有两端强而中间弱的分段活动特点;深震区P轴平均走向为288°,倾角约31°,断裂活动以逆断为主;郯庐断裂带北段附近浅震P轴走向以NEE-SWW向为主,倾角平均26°,T轴走向以NNW-SSE向为主,倾角平均23°,断裂活动以走滑和逆断为主。浅震区和深震区主压应力方位存在差异,这可能是在西太平洋板块低角度高速水平消减产生的NWW向挤压应力作用下,郯庐断裂北段右行走滑派生的次级应力场的影响。

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