Evidence for the most recent rupture of the San Bernardino strand, San Andreas Fault in the 13th to 14th century AD, Burro Flats near Banning, California Evidence for the Most Recent Rupture of the San Bernardino Strand, San Andreas Fault in the 13th to 14th Century AD, Burro Flats near Banning, California. There was no evidence for younger events.
Structural evidence includes truncation and offset of units.
Radiocarbon samples that constrain the age of the event horizon include two samples of peaty soil, and one sample of horizontal plant fibers separated from a peat layer. Calibrated calendar ages constrain the event to have occurred shortly before AD 1225 - 1395. No evidence exists at Burro Flats for younger ruptures that correspond to either the A.D. 1700 or 1812 events found in the Wrightwood, Pitman Canyon and Pallett Creek areas. Furthermore, evidence of the A.D. 1680 event at Indio does not appear at Burro Flats. The behavior of the San Andreas Fault at Burro Flats therefore appears to be in striking contrast to the fault's behavior to the northwest and southeast, at Wrightwood and Indio, respectively.