2019-07 Ridgecrest地震及其余震的双差重定位分析

选取加州理工学院（Caltech）、美国地质调查局（USGS）及南加州地震数据中心（SCEDC）的震相观测报告和数字波形数据，结合波形互相关技术，利用双差定位方法单独和联合反演Ridgecrest M_W6.4前震、M_W7.1主震及震后1个月内M_W≥2.5余震的震源参数。精定位结果显示，2 098次地震事件形成4个事件簇，得到高达97%重定位率的震源参数；地震序列走时残差为65 ms，互相关走时残差为57 ms。精定位后震中位置线性特征更为显著，震群空间分布呈L型和T型特征，余震展布长约90 km，宽约25 km。定量分析地震活动与断层构造的关系，结果表明，Ridgecrest地震序列始于深部并向浅部区域传播，震源深度主要分布在4~8 km范围，呈分段条带特征，揭示Ridgecrest地震序列对该处规模不一的多断层构造组成的复杂断层系造成破坏，小湖断裂带为地震序列的发震断层。

Analysis of the July 2019 Ridgecrest Earthquake and Aftershocks Using Double-Difference Relocation

Seismic phase observation reports and seismic waveform data are selected from the California Institute of Technology and US Geological Survey and the Southern California Earthquake Data Center. Relocated hypocenters of MW6.4 foreshock and MW7.1 mainshock of Ridgecrest earthquake and its aftershocks with MW≥2.5 within one month after the earthquake are independently and jointly inversed using double-difference location algorithm combined with the waveform cross-correlation technique. The relocation results show that four event clusters are formed from 2 098 events, and seismic source parameters with a relocation rate of up to 97% are achieved. The travel time residual and cross-correlation travel time residual of earthquake sequences decreases to 65 ms and 57 ms, respectively. Compared with the original result, the linear features of the epicenter are more significant after relocation, with aftershocks forming an L-shaped and T-shaped pattern, respectively. The length of aftershocks is about 90 km and the width is about 25 km. The relationship between seismic activity and fault structure is quantitatively analyzed and the results state that the Ridgecrest earthquake sequence starts deep and propagates to the shallow surface gradually. The predominant range of depth distribution is from 4 km to 8 km, showing the characteristics of segmented bands, revealing that the Ridgecrest sequence destroyed the complex fault system composed of multi fault structures with different scales, and the Little lake fault zone is the seismogenic fault of the Ridgecrest earthquake sequence.