Oceanside and Thirtymile Bank blind thrusts: Implications for earthquake hazards in coastal southern California

Abstract

We define an active blind thrust system in offshore southern California that extends from Los Angeles south to the United States–Mexico international border. These blind thrusts formed by tectonic inversion of Miocene extensional detachments. We attribute the 1986 Oceanside (ML 5.3) earthquake, local uplift of marine terraces, seafloor fold scarps, and observed geodetic convergence to motion on these faults. Single and multisegment fault rupture scenarios suggest the potential for large (M 7.1–7.6) but infrequent earthquakes that would affect the Los Angeles and San Diego metropolitan areas.