1970年1月5日云南通海地震的震源特征

本文根据长周期地震仪记录的P波资料,研究了通海地震（M_s=7.7）的震源参数和破裂过程。该地震沿着北西西走向的曲江断裂扩展,为非对称的双侧破裂,北西侧为24公里,东南侧为32公里,平均破裂速度为2.3公里/秒;地震矩为4.34×10²⁶达因·厘米,应力降为21巴;地震前后存在无震滑动;余震除沿主破裂面分布外,还大量集中于主破裂面的东南端的扩展分支上,并与主破裂面偏离80°左右。

THE FOCAL CHARACTERISTICS OF THE TONGHAI EARTHQUAKE,YUNNAN PROVINCE,ON JANUARY 5,1970

The fracture processes and focal parameters of the Tonghai earthquake （M_s=7.7） which occurred on January 5, 1970 are estimated from the data of the P waves. This earthquake occurred on the Qujiang （#） fault striking NWW and propagated nearly, along it with an asymmetric bilateral fracture which propagated 26 km northwestward and 40 km southeastward with an average velocity of 2.3 km/sec. Estimation of the seismic moment of this earthquake by spectral analysis gives a value of 4.34#1026 dyne-cm. This value is considerably lower than that given by geodetic data. This difference indicates that some aseismic slips had taken place on the fault before and after Tonghai earthquake.As in Tangshan （#） earthquake, most of the aftershocks of this earthquake occurred along the fracture branches at both ends of the main fault. On the other hand, the fracture branch on the southeast end is noticeable for Tonghai earthquake. This fracture branch is located in the dilatational quarters and makes an angle of about 80 with the main fault.