远场记录反演2016年4月17日厄瓜多尔Mw7．8地震破裂过程

Rupture process of the 17 April 2016 Ecuador M_w7.8 earthquake by teleseismic records

本文选取震中距30°~90°远场40个台站垂直向P波位移记录,采用非负最小二乘法结合多时间视窗技术,反演了2016年4月17日厄瓜多尔Mw7.8级地震震源破裂过程。采用棋盘测试对数据的反演能力进行了分析,表明最佳分辨率为子断层尺寸10 km×10 km。反演结果表明:断层破裂速度约为3.2 km/s,破裂发生在深度27 km以上,有两个凹凸体。第1个凹凸体在初始破裂点附近,最大滑动量2.0 m,以逆冲错动为主,破裂持续14 s,释放14%的地震矩。第2个凹凸体在初始破裂点西南侧50 km处,最大滑动量3.4 m,为逆冲兼左旋走滑,破裂持续20 s,释放69%的地震矩。整个断层面破裂持续50 s,释放地震矩5.3×1020N·m。对反演参数的分析表明,结果对震源时间函数的形式不敏感;远场速度记录反演结果相比位移记录,有更多的子断层参与破裂,地震矩和残差都变大。

Using teleseismic vertical displacement records of 40 stations with epicenter distance in 30° ~ 90°, the 17 April 2016 Ecuador Mw7. 8 earthquake is inversed by non-negative least square method and multiple time windows. The resolving power of the data was investigated by checkboard tests, which showed that the best subfault size was 10 km × 10 km. The inversion results show that the rupture velocity was 3.2 km/s and concentrated in the deep above 27 kin. The fault had two asperities. One was around the initial rupture point, which peak slip was 2.0 m and was characterized by thrust motion. The rupture duration time was 14 s and released 14% of the total moment. The other located in the area 50 km southwest of the epicenter. The peak slip was 3.4 m and characterized by thrust and left lateral strike-slip. Duraion of the rupture was 20 s and released 69% of the total moment. The entire rupture lasted for 50 s and the total seismic moment released was 5.3 × 10^20 N · m. Analysis of the inversion parameters showed that, sult of diplacement, the velocity error were larger. the result was insensitive to the form of the slip rate function. result had more subfauhs participate in the rupture, and the Compared to the remoment and residual