Precise knowledge of the age and magnitude of past earthquakes is essential for characterizing models of earthquake recurrence and key to forecasting future earthquakes. We present 28 new radiocarbon analyses that refine the chronology of the last five earthquakes at the Bidart Fan site along the Carrizo section of the south central San Andreas Fault, which last raptured during the Fort Tejon earthquake in A.D. 1857. The new data show that the penultimate earthquake in the Carrizo Plain occurred not earlier than A.D. 1640 and the modeled 95th percentile ranges of the three earlier earthquakes (and their mean) are A.D. 1540-1630 (1585), A.D. 1360-1425 (1393), and A.D. 1280-1340 (1310), indicating an average time interval of 137 ± 44 years between large earthquakes since A.D. 1310 ± 30. A robust earthquake recurrence model of the Carrizo section will require even more well-dated earthquakes for thorough characterization. However, these new data imply that since A.D. 1310 ± 30, the Carrizo section has failed more regularly and more often than previously thought.
ASJC Scopus subject areas
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science