巴基斯坦7.8级地震前新疆独山子台跨断层位移变化初析

2005年10月8日巴基斯坦发生7.8级强烈地震, 震前新疆独山子台横向位移测量仪(GDW)记录到了较大变化。 根据独山子台记录到的断层形变资料, 结合区域内其他观测资料及区域地震活动进行了初步分析, 结果表明: ① 独山子-安集海断裂现今活动是以右旋逆冲运动为主, 其断层垂直向活动速率为0.12 mm/a, 水平向活动速率为0.25 mm/a。 巴基斯坦7.8级地震前横向位移观测结果显示断层右旋滑动速率增强, 其日平均速率达1.79 mm/d, 是正常日平均活动速率的12.8倍。 ② 独山子台MD系列数字化跨断层形变观测资料, 对独山子台300 km范围内的M_S≥5.0地震, 震前均有明显的地震前兆异常显示; 对1000 km范围内的M_S≥7.5地震, 亦有孕震过程显示。 ③ 巴基斯坦7.8级地震后约15分钟, 独山子台的MD系列数字化跨断层形变测量仪先后记录到了同震变化, 这也进一步说明该测量仪具有高精度、 宽量程、 抗干扰能力强的特点。

A preliminary study on the cross-fault displacement variation at Dushanzi Station in Xinjiang, China, before the M7.8 earthquake in Pakistan

A strong earthquake with M7.8 occurred on October 8, 2005 in Pakistan. The lateral displacement meter (GDW) at Dushanzi station of Xinjiang Region shows significant variation before this earthquake. This paper makes a preliminary analysis on the fault deformation data from Dushanzi station together with other observations and seismicity data in the region. The result indicates that: ① The Dushanzi-Anjihai Fault is currently dominated by thrust-right lateral movement, the vertical movement rate is 0.12 mm/a, the horizontal rate is 0.25 mm/a. Before the M7.8 earthquake in Pakistan, the observational result of lateral displacement indicates that the rate of right -lateral slipping of the fault increased to 1.79 mm/day, being 12.8 times of the normal daily rate. ② The observation data of MD digital cross-fault deformation meter at Dushanzi station have shown clear precursory changes before M_S≥5.0 earthquakes within 300km from Dushanzi station, and also shown some signs for the preparation process of M_S≥7.5 earthquakes within 1000 km from the station. ③ About 15 minutes after the Pakistan earthquake, the cross-fault deformation meter at Dushanzi station recorded co-seismic variations. This further proves that the instrument is of high precision, wide range, and good anti-interference capability.