【摘要】 利用2000年3月至2014年4月江苏及邻区数字地震波形资料,采用P波、S波初动和振幅比求解方法计算了江苏南部地区123次中小地震震源机制解。分析震源机制解特征表明,研究区中小地震震源类型以走滑型为主,其次为正断层类型,P、T轴优势方向分别为NEE—SWW和NNW—SSE向。依据盆地和断裂发育、历史及现代中小地震分布、震源机制等特征将研究区划分为A区和B区。采用Gphart方法分别反演了这两个区域应力张量,结果显示:A区最大主应力方位角为78°,倾角为23°,最小主应力方位角为340°,倾角为17°;B区最大主应力方位角为60°,倾角为25°,最小主应力方位角为330°,倾角为1°。两个分区应力场结果的差异显示了局部应力场的不均匀性,体现了局部地区地质条件、构造活动等差异性。各分区应力场特征与区内的中强地震震源机制特征较为一致,这在一定程度也佐证了反演结果的可靠性。更多还原

【Abstract】 Using the digital seismic waveform data in Jiangsu and its adjacent area during M ar., 2000 and Apr.,2014,we calculated the focal mechanisms of 123 moderate and small earthquakes in southern Jiangsu area by the method of amplitude ratio of P wave and S wave. The characteristics of the focal mechanism solution shows that the main type of the small and moderate earthquake in the study area is strike-slip type,secondly for normal fault type,and the predominant orientations of P and T axes are NEE—SWW and NNW —SSE respectively. On the basis of the development of basin and faults,the distribution of historical and modern earthquakes and the characteristics of focal mechanism etc.,we divided the study area into A and B regions and inverted the stress tensor of the two regions by Gphart method. The result shows that the azimuth and dip of maximum principal stress is 78° and 23° in A region,is 60° and 25° in B region respectively,and the azimuth and dip of minimum principal stress is 340° and 17° in A region,is 330° and 1° in B region respectively. The differences of stress field in the two regions showed the heterogeneity of the regional stress field,which reflected the differences of geological conditions and the tectonic activity etc.. The characteristics of stress field in the two regions were coincident with focal mechanism of the modern-strong earthquake in the study area,which proved the reliability of the inversion results.更多还原