2014 年云南盈江Ms 6.1 地震震源机制研究

The study on focal mechanism of the MS 6.1 Yingjiang， Yunnan earthquake

摘要:

利用中国数字地震台网记录的区域宽频带波形，通过频率域和时间域多步反演，研究了2014 年云南盈江MS6． 1 地震基于点源模型的震源机制解和有限断层模型。考虑到使用不同的波形资料类型和简化的一维速度模型等因素对震源参数反演结果的影响，进行了大量的测试比较。结果表明，使用近震波形和本区域简化一维速度模型M1，波形拟合误差最小。基于点源模型的震源机制解显示此次地震发震断层面参数分别为:走向176° /倾角84° /滑动角－ 173°，表现为一次右旋走滑错动为主的事件。矩心在水平方向上位于震中( 24． 99° N，97． 84°E)北东向约7km，最佳波形拟合矩心深度7km。平均总标量地震矩M0 为7． 56 × 1017 N·m，计算成矩震级为MW5． 8。进一步模拟高达0． 5Hz 的高频波形，获得了盈江地震的有限断层模型，结果显示此次地震未表现出明显的破裂方向性。破裂半径约10km，整个破裂面积为267. 2km2，平均滑动量约0． 05m，破裂在5 s 内释放了大多数能量。震后0 ～ 2s 内，破裂以孕震点为中心向四周同时扩展，在深度7 ～ 17km 内释放了部分能量。2s 后，破裂朝断层面顶部和沿走向两侧进一步延伸，约5s 后破裂基本停止。

Abstract:

We employ multistep inversions in the frequency or time domain to infer the pointsource and finite-fault model of the 2014 MS 6. 1 Yingjiang，Yunnan earthquake，mainly using regional broadband seismic waves recorded by the Chinese Digital Seismic Network． We take into account some factors，which could bring possible effects on the inverted result，consisting of different datasets and simplified 1-D velocity models． The result indicates the misfit between observed waves and synthetics is better，if we use the regional waves and the 1-D velocity model (M1) in this studied area． This event occurs on a true rupture plane ( strike = 176° / dip = 84° / rake = － 173°)，showing a right-lateral strike-slip faulting． The horizontal centroid locates at nearly 7km northeast of the epicenter (24. 99°N /97. 84°E)，and the best-fitting centroid depth is about 7km． The total scalar moment M0，is retrieved with an average value of 7. 56 × 1017N·m ( or moment magnitude MW 5. 8 ) ． We make use of the high-frequency ( up to 0. 5Hz) data to reconstruct the finite fault model． The result shows that the rupture direction of this event is not obvious with a radius of 10km． The total rupture area is about 267. 2 km2 with an average slip of 0. 05m． Most of energy is released within about 5s． From 0s to 2s，the energetic rupture starts at the nucleation center，then propagates bilaterally along the fault plane． Part of energy is released in between 7km and 17km depth． After 2s，the rupture mainly extends to the top and along the strike of the fault plane． In the end，the rupturing ceases at about 5s．