2019 Ridgecrest, CA Earthquake Sequence

On July 7 2019, the largest earthquake since the Landers event jostled Southern California near the town of Ridgecrest. The faults that slipped during this event were not previously mapped by geologists and thus, caught many by surprise. There is a larger fault zone immediately south of Ridgecrest called the Eastern California Shear Zone that relieves some of the stress caused by the North American and Pacific tectonic plates. In this fault zone lies the Garlock fault, which is capable of hosting magnitude 7 and larger events. Satellite were able to document the change in surface deformation before and after the Ridgecrest event and showed that while the Garlock fault didn't slip quickly the way a big earthquake does, it did creep very slowly over nearly 15 miles.

In our study, we examined how both static and dynamic elastic stresses from the Ridgecrest mainshock influenced the nearby Garlock fault, which didn't slip during this sequence. We show that the Garlock fault received a series of positive peak stresses during mainshock rupture, and any one of these could have provided the energy to make the Garlock fault creep. The dynamic modeling I spear-headed captured the temporal evolution of near-field stress changes and was able to match first-order seismological observations made about the mainshock.