Oblique Blind Faulting Underneath the Luzon Volcanic Arc During the 2022 M w 7.0 Abra Earthquake, the Philippines

Unknown seismogenic structures lurking beneath convergent margins introduce substantial uncertainty in seismic hazard assessments. In northwestern Luzon, the M w 7.0 Abra earthquake on 27 July 2022 highlights the seismic activity along an unmapped blind fault underneath the Cordillera Central. By integrating coseismic displacements constrained by radar satellite imagery and Global Navigation Satellite System, we image oblique coseismic slip at 11–22 km depth with peak slip of ∼1 m beneath the Philippine Fault Zone in northern Luzon. The southward propagation of coseismic slip and aftershocks terminated at a distance of 50 km from the northern end of the 1990 Luzon earthquake rupture, leaving a seismicity gap in between. Coulomb stress changes of reaching 2 bars are imparted at the shallow portions of the Vigan‐Aggao and Abra River faults, where the updated 100‐year seismic potential is increased to M w 7.0–7.7, given the thick seismogenic layer of ∼30 km in northern Luzon. On 27 July 2022, the M w 7.0 Abra earthquake hit northwestern Luzon, the Philippines, killing 11 people, damaging more than 30,000 buildings, and causing US$34 million worth of damage. The earthquake occurred on a previously unrecognized deep fault with no observable surface ruptures. In this study, we collected coseismic displacements from Global Navigation Satellite System and Interferometric Synthetic Aperture Radar to investigate the source fault and coseismic slip distribution. Our model shows that the coseismic slip occurred beneath the Philippine Fault Zone in northern Luzon at a depth of 11–22 km. The coseismic slip and aftershocks propagated southward and terminated at a distance of 50 km from the northern tip of the 1990 Luzon coseismic surface rupture. This leaves a seismicity gap between latitudes 16.5°N–17°N along the Philippine Fault Zone. The mainshock‐induced stress perturbation on the nearby active faults, together with the unusually thick seismogenic layer on the northern Philippine Fault Zone, implies a high seismic hazard in Luzon. Successive crustal deformation and seismicity monitoring will provide valuable constraints for the energy budget of earthquakes across northern Luzon, where local communities are threatened by inland crustal earthquakes and megathrust events in the future. Global Navigation Satellite System and Sentinel‐1 Aperture Radar reveal the Abra rupture on an oblique blind fault beneath northern Luzon The coseismic rupture brought the shallow parts (