LAUSR

Abstract We present a Coulomb stress analysis for the July 4th Mw 6.4 and July 5th Mw 7.1 earthquakes of the 2019 Ridgecrest, California earthquake sequence. We find that the Coulomb stress on the Mw 6.4 rupture plane was increased by the 1872 Owens Valley earthquake and slightly increased by the 1952 Kern County earthquake. Like- wise, the rupture plane of the July 5th Mw 7.1 earthquake was promoted by both the Owens Valley and Kern County earthquakes, as well as being promoted slightly by the 1992 Landers earthquake and the 1999 Hector Mine earthquake. To investigate the regional Coulomb stress change from the Ridgecrest earthquake sequence, we calculate Coulomb stress change on nearby faults from both the Mw 6.4 and Mw 7.1 earthquakes. We find that the Mw 6.4 earthquake promoted failure at the epicen- ter of the Mw 7.1 earthquake, which struck 34 h later. Furthermore, the Mw 6.4 and Mw 7.1 Ridgecrest earthquakes increased Coulomb stress on the Garlock fault to the west of the rupture and decreased Coulomb stress to the east. The Panamint Valley fault was relaxed by the Ridgecrest earthquakes. The most significant stress change is an increase of Coulomb stress to the south of the Ridgecrest Sequence on the nearby Blackwater fault. The Blackwater fault, situated between the Lan- ders and Ridgecrest earthquakes, was loaded significantly by the Mw 7.1 Ridgecrest earthquake (up to 0.12 MPa) and by lesser amounts by the Landers and Hector Mine earthquakes. Of the known active faults in the region, including the Garlock fault, the Blackwater fault appears to have been loaded the most by the Ridgecrest earth- quakes.