Western Pacific double subduction drives Gulf of California rifting

Continental rifting reflects the balance between tectonic forces and lithospheric strength, yet the mechanisms of breakup remain debated. Rapid rifting of the Gulf of California oblique rift (GOCOR) ~6 million to 8 million years ago is a key example; it may have resulted from the lithosphere responding to external kinematics or acceleration of long-lived extension. The dynamics of either scenario remain incompletely understood. In this study, we highlight that the rapid rifting of the GOCOR coincides with the initiation of Western Pacific double subduction. Using three-dimensional geodynamic models, we show that such subduction reorganization can transmit extensional stresses of ~5 to 15 megapascals across the Pacific plate, loading the GOCOR and the southern San Andreas fault. Subduction reorganization may represent the missing driver for the initiation of rapid GOCOR rifting within a preconditioned lithosphere and may be an overlooked tectonic force behind other rifting events.