2000年姚安M_S6.5地震3.0≤M_L<5.0余震的地震矩张量反演

Earthquake Moment Tensor Inversion of the Aftershocks (3.0≤M_L<5.0) of the 2000 Yao'an M_S6.5 Earthquake

建立合于云南地区的速度结构模型,对云南数字地震台网记录的2000年姚安MS6.5地震3.0≤ML<5.0余震的垂直分量进行频率域内的地震矩张量反演。结果表明:矩张量分解得到纯膨胀(各向同性)分量P、纯剪切(双力偶)分量M0和补偿线性矢量偶极C三部分,其中纯剪切(双力偶)分量M0占主要部分,表明地震的震源破裂过程以剪切破裂为主。从余震震源机制解可知,NW—NWW方位的节面占主导,结合余震分布尺度可以判断发震断裂是北西向的断裂。

From thousands of aftershocks of the Yao＇ an Ms6. 5 earthquake in 2000, we selected 19 ones （3.0≤ML 〈 5.0） to do a moment tensor inversion in frequency domain using the velocity model that agrees with the Yunnan area. After decomposing moment tensor, we obtain three parts： shear dislocation source, explosion component and compensation linear vector dipole. Among them, explosion component is predominant, which shows the shear fracture to be the main fracture of the earthquake. According to the focal mechanism solution and distribution of the aftershocks, we judge that the main plane is in NW-NWW direction, and the causative fault extends along NW-direction.