Tidal Modulation of Seismicity Between the Mw 6.4 and Mw 7.1 2019 Ridgecrest Earthquakes

Tidal triggering of seismicity occurs preferentially when a region is subjected to being in a state of critical stress, suggesting that tidal stress may provide a useful tool for providing information about the state of stability of faults. Few studies have been conducted to explore the distinct behavior of tidal sensitivity with foreshock-mainshock-aftershock sequences. In this study, we integrated Schuster's test and b value to examine the correlation between tidally induced stresses and the 2019 Ridgecrest earthquake sequence. Schuster's results show a strong correlation between tidal stresses and foreshocks and a weak correlation with aftershocks. The spatiotemporal evolution of b value suggests that it is characterized by a low b value between the Mw 6.4 foreshock and the Mw 7.1 mainshock, and it slowly goes back to the background level after the mainshock. The low Schuster probability and b value indicate that the fault is under a high-stress state during the foreshock sequence, making it sensitive to tidal stress modulation.