Joint earthquake ruptures of the San Andreas and San Jacinto faults, California, USA

Abstract Large, multi-fault earthquakes increase the threat of strong ground shaking and reshape probability future events across a system faults. Fault junctions act as conditional barriers, or earthquake gates, that stop most but permit junction-spanning when stress conditions are favorable. Constraining physical favor requires information on frequency isolated versus activate faults through junction. Measuring this is challenging because dating uncertainties limit correlation paleoseismic at different faults, requiring direct approach to measuring rupture an gate. We show documentation finite-element modeling secondary fault slip co-rupture San Andreas Jacinto (California, USA) Cajon Pass gate occurred least three times in past 2000 yr, recently historic 1812 CE earthquake. Our models gate-breaching taper steeply halt abruptly they transfer between Comparison independent chronologies shows 20%–23% co-ruptures Pass.