Abstract: Using the seismic waveform data recorded by regional seismic network, we calculated focal mechanism solutions of 825 moderate and small earthquakes in Shandong-Jiangsu-Anhui segment of Tancheng-Lujiang Fault zone and its adjacent area from 2001 to 2016 and collected focal mechanism solutions of 323 earthquakes from 1970 to 2000. A total of 1148 focal mechanism solutions were obtained. With the focal mechanism solutions as the input data, we adopted the method of damped regional-scale stress inversion to calculate the variation characteristics of 1.0°×1.0°spatial stress field in the study area. The result shows that the maximum principal stress direction of Shandong-Jiangsu-Anhui segment of Tancheng-Lujiang fault zone presenting the feature of spatial continuity change, the overall trend of rotation existing in EW, NEE and NE direction from west to East. There exists partial differences. Taking the Tancheng-Lujiang fault zone as the boundary, there are differences in the stress field between the East and the West. The maximum principal stress directions of the North China Plain block to the West are mainly EW and NEE direction; while, the east Shandong Yellow Sea blocks show NEE and NE directions. It is reflected that there are different effects on different blocks caused by different power sources which is inclined westward and extending to the top of the upper mantle in the Tancheng-Lujiang fault zone. The boundary effect of the Tancheng-Lujiang fault zone is significant. Along the Tancheng-Lujiang fault zone, there is a significant difference in the stress field between the north and the south. The maximum principal stress direction in the 33°N and north latitude area is anticlockwise deflected from west to east. The direction of maximum principal stress begins to deflect clockwise from west to east in the area of 32°N and to the south. The direction of the maximum principal stress between 31-33°N and 120-122°E is complex. It is characterized by radial distribution .The region locates in a very complex tectonic environment, which is affected by the subduction of Yangtze block, the Western subduction of North China plate, Pacific plate and Philippine Plate. The moderate strong seismicity in the study area is obviously related to the tectonic stress environment. The area with complex tectonic stress field is almost the area with moderate strong earthquake activity.

Key words: focal mechanism, stress field, dynamics, Shandong-Jiangsu-Anhui segment of Tancheng-Lujiang fault zone

摘要： 利用区域台网数字地震波形，计算得到了2001～2016年郯庐断裂带鲁苏皖段及邻区825次中小地震震源机制解，并收集了1970～2000年模拟记录时期323个震源机制解，共计获得1148个震源机制解。以震源机制解作为输入数据，采用阻尼应力张量方法反演获得了研究区1.0°×1.0°空间应力场变化特征。结果显示郯庐断裂带鲁苏皖段最大主应力方向呈现空间连续性变化特征，由西向东总体呈EW向、NEE向、NE向逆时针趋势性旋转，局部存在差异；以郯庐断裂带为界，东西两侧应力场存在差异性，以西的华北平原地块最大主应力方向主要表现为近EW向和NEE向，而以东的鲁东黄海地块则表现为NEE向和NE向，反映了西向倾斜延伸至上地幔顶部的郯庐断裂带造成各动力源对不同块体影响存在差异，郯庐断裂带边界作用显著；沿郯庐断裂带北纬33°为界，南北地区应力场存在显著差异，北纬33°及以北地区最大主应力方向由西向东出现逆时针偏转，而北纬32°及以南地区，最大主应力方向由西向东开始出现顺时针偏转迹象；在北纬31－33°，东经120－122°之间最大主应力方向较为复杂，呈放射状分布特征，该区域处于非常复杂的构造环境下，受到扬子陆块俯冲华北陆块和太平洋板块与菲律宾板块西向俯冲的共同作用；研究区中强地震活动与构造应力环境相关明显，构造应力场复杂的地区往往是中强地震活跃的地区。

关键词: 震源机制, 应力场, 动力学, 郯庐断裂带鲁苏皖段