Late Quaternary uplift and earthquake potential of the San Joaquin Hills, southern Los Angeles basin, California

Analysis of emergent marine terraces in the San Joaquin Hills, California, and Th-230 dating of solitary corals from the lowest terraces reveal that the San Joaquin Hills have risen at a rate of 0.21-0.27 m/k.y. during the past 122 k.y. Movement on a blind thrust fault in the southern Los Angeles basin has uplifted the San Joaquin Hills and has the potential to generate an M-W 7.3 earthquake within this densely populated area. Our structural modeling suggests that the fault dips to the southwest and slips at similar to 0.42-0.79 m/k.y., yielding an estimated minimum average recurrence interval of similar to 1650-3100 yr for moderate-sized earthquakes. Recognition of this blind thrust extends the known area of active blind thrusts and fault-related folding southward from Los Angeles into coastal Orange County.