Change of seismicity across the Ridgecrest earthquake area

Abstract

Seismicity parameters can simplify the understanding of the intrinsic complications that arise in the state of stress across the hypocentral areas of interest. We studied variations of the spatial and temporal changes of these parameters by three different methods: maximum curvature, entire magnitude range, and hierarchical space time point process model across the July 2019 Ridgecrest earthquake region. In order to verify the estimations, the Utsu’s test has also been applied. According to the results, seismicity parameters show heterogeneous distribution in this area. The implemented methods provide comparable b-values; however, the b-value displays relatively lower values in northwest and higher values in southeast. Seismicity rate comparison for two periods before and after the M7.1 shock favors change in the b-value. Based on the employed catalog, seismic activity accelerated about half an hour before the M6.4 event. Whereas 2 days before the M7.1 earthquake, seismic activity was low and accelerated approximately 1 day prior to the same event. So there is a clear difference in pre M6.4 and pre M7.1 seismic activity patterns. Moreover, the b-value and magnitude of completeness show decrease before the M7.1 shock, and spatial changes of the b-value expose obvious differences with depth.