Solid-earth tidal modulations of 2019 Ridgecrest earthquake sequence, California: any link with Coso geothermal field?

Abstract

We report solid-earth tidal modulation of early aftershocks of the July 2019 Ridgecrest earthquake sequence, which occurred close to the southeastern edge of the Coso geothermal field. We found that the frequency of early aftershocks in the northern part, close to the Coso geothermal field, was modulated by the solid earth tides as they exhibit a strong correlation with the peak shear stress and Coulomb stress imparted by the solid earth tides. However, aftershocks that occurred farther south of the Coso geothermal field in the same sequence exhibit a weak correlation with the solid earth tidal stress. Our analysis implies that the tidal modulation of the earthquake sequence in the northern part is due to its vicinity to the Coso geothermal fields in southern California, which contain high-pressure fluids and are well known for their susceptibility towards tidal triggering.