The Wilmington Blind-Thrust Fault: An Active Concealed Earthquake Source beneath Los Angeles, California

We define the Wilmington blind-thrust as a tectonically active fault capable of generating large damaging earthquakes, through analysis of 2D and 3D seismic reflection surveys, petroleum and water wells, and recent mapping of groundwater aquifers in the southwestern Los Angeles basin. This overturns the long-held view that the fault became dormant in the Late Pliocene, barring its inclusion in state-of-the-art regional earthquake hazard assessments. The size of the fault suggests that it is capable of generating moderate-magnitude earthquakes (M-w 6.3-6.4), whereas potential linkages with other nearby faults (e.g., Huntington Beach, Torrance, and Compton) pose the threat of larger multisegment events (M-w > 7). These earthquakes would directly impact the overlying Ports of Los Angeles and Long Beach, as well as the broader Los Angeles metropolitan area.