2007年宁洱6.4级地震序列视应力研究

Apparent Stress of the 2007 Ning'er,Yunnan,M_S6.4 Earthquake Sequence

利用云南省区域数字化观测资料,估算了2007年宁洱6.4级地震序列视应力,结果表明:①宁洱震区视应力在空间分布上明显呈NE向展布,视应力较高的地震大都分布在地震辐射能较高的地区;②宁洱6.4级主震发生的前4天,平均视应力为0.95MPa,主震发生4天以后,平均视应力为0.27MPa,恢复到云南平均背景应力水平;③视应力随拐角频率的增加而减小,大致呈负相关:lgσa=-0.36f+0.37,视应力与震源深度之间未发现明显的依赖关系。

We calculated the apparent stress of the 2007 Ning＇er, Yunnan, Ms6.4 earthquake sequence using the data recorded by Yunnan Regional Digital Seismic Network. The result shows： （ 1 ） the apparent stress distributes obviously along NW-direction in the Ning＇er earthquake .area, and the earthquake with high apparent stress mostly locates in an area with high earthquake radiation energy; （ 2 ） within 4 days after the main shock, the average apparent stress is 0.95 MPa, after that it is 0.27 MPa, come back to the average apparent stress level of Yunnan; （ 3 ） the apparent stress reduces with increasing comer frequency, generally is negatively correlative： lgσa=-0.36f＋0.37, and obvious dependent relation has not been found between the apparent stress and the focal depth.