Spatiotemporal Variations of the Frequency-Magnitude Distribution in the 2019 7.1 Ridgecrest, California, Earthquake Sequence.

Significant seismic activity has been witnessed in the area of Ridgecrest (Southern California) over the past 40 years, with the largest being the 5.8 event on 20 September 1995. In July 2019, a strong earthquake of 7.1, preceded by a 6.4 foreshock, impacted Ridgecrest. The mainshock triggered thousands of aftershocks that were thoroughly documented along the activated faults. In this study, we analyzed the spatiotemporal variations of the frequency-magnitude distribution in the area of Ridgecrest using the fragment-asperity model derived within the framework of non-extensive statistical physics (NESP), which is well-suited for investigating complex dynamic systems with scale-invariant properties, multi-fractality, and long-range interactions. Analysis was performed for the entire duration, as well as within various time windows during 1981-2022, in order to estimate the parameter and to investigate how these variations are related to the dynamic evolution of seismic activity. In addition, we analyzed the spatiotemporal value distributions along the activated fault zone during 1981-2019 and during each month after the occurrence of the 7.1 Ridgecrest earthquake. The results indicate a significant increase in the parameter when large-magnitude earthquakes occur, suggesting the system's transition in an out-of-equilibrium phase and its preparation for seismic energy release.