紫坪铺水库库区地震精定位研究及分析

利用双差定位法, 对紫坪铺水库台网8个地震台站记录到的2004年8月16日至2008年5月10日的1569个小震进行重新定位。 结果显示, 重新定位后的小震主要集中分布在龙门山推覆构造带的中央北川—映秀断裂、 前山灌县-江油断裂和后山汶川—茂汶断裂上, 其中大部分地震位于北川—映秀断裂并收敛于紫坪铺水库的两端, 走向NE向; 震源深度集中在5~15 km范围内, 平均深度为7.8 km, 15~30 km也有少量地震发生。 水库区域小震活动频度与水库水位存在一定的相关性。 精定位后, 到时残差的均方根平均值为0.048 s, 震源位置的估算误差在水平方向上平均为0.63 km, 在垂直方向上平均为0.51 km。 文中还讨论了紫坪铺水库区震源分布和地质构造的关系。

Accurate Relocation and Analysis of Earthquakes in the Zipingpu Reservoir Area, Sichuan, China

We use double difference location method to relocate 1569 small earthquakes recorded by 8 seismic stations of the Zipingpu reservoir network from August 16, 2004 to May 10, 2008. The results show that after relocation, the earthquake distribution is from spatial discretization and gridding to concentrated distribution, and the small earthquakes relocated are mainly concentrated in central Beichuan-Yingxiu fault, frontal Guanxian-Jiangyou fault and retral Wenchuan-Maowen fault of the Longmen Mountains. Most of the small earthquakes are located in the Beichuan-Yingxiu fault and converge to both ends of the Zipingpu reservoir, and occurred at the depth of 5~15 km,and a few at depth of 15~30 km, and the mean depth is 7.8 km. Seismic frequency of the Zipingpu Reservoir region has a correlation with the reservoir water level. The average root-mean-square of travel time residual after relocation is 0.048s, the horizontal average error is estimated to be 0.63 km, and the average vertical error had been controlled less than 0.51km. This paper also discussed the relation between location image and the geological structure.