Automated moment tensor inversion using 3D Green’s Functions: Application to the LA basin and the 2019 Ridgecrest sequence

Zhongwen Zhan, & Xin Wang

Published August 13, 2019, SCEC Contribution #9545, 2019 SCEC Annual Meeting Poster #257

Earthquake focal mechanisms put primary control on the distribution of ground motion, and also bear on the stress state of the crust. Most routine focal mechanism catalogs still use 1D velocity models in inversions, which may introduce large uncertainties in regions with strong lateral velocity heterogeneities. Here, we develop an automated waveform-based inversion approach to determine the moment tensors of small-to-medium-sized earthquakes using 3D SCEC Community Velocity Models (CVMs). We apply the method to the 2019 Ridgecrest earthquake sequence and the earthquakes in the Los Angeles region since 2000. For the 2019 Ridgecrest sequence, our moment tensor catalog, which contains about 150 earthquakes, reveals both along-strike and along-dip change of fault geometry at the location where the M6.4 event stopped and the M7.1 event started. We suggest that the complex subsurface fault geometry partially controlled the rupture patterns of the 2019 Ridgecrest sequence. For the earthquakes in the Los Angeles region, we produce a new moment tensor catalog with a completeness of ML≥3.5. Our new catalog also features more accurate focal depths and moment magnitudes and will be available for further seismological and geological investigations, as well as contributing to mitigating the seismic hazard and risk in the area.

Citation
Zhan, Z., & Wang, X. (2019, 08). Automated moment tensor inversion using 3D Green’s Functions: Application to the LA basin and the 2019 Ridgecrest sequence . Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes