Project Abstract
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To characterize southernmost San Andreas fault paleoseismicity we initiated recovery of a stratigraphic earthquake record at the Salt Creek-South site (SCS). Salt Creek is the only “deep water” Lake Cahuilla site, 70 m below the high shoreline, with an additional ~60-years of lacustrine sediment record per lake episode relative to high shoreline sites. Considering that we are observing at least five lake episodes, this translates into an additional 300 years of record and thus potentially providing more complete event-recording than high shoreline sites (e.g. Indio and Coachella) . The southernmost San Andreas fault (SSAF) is one of the most likely faults to generate a great earthquake in southern California in the foreseeable future (WGCEP, 1995). Its high slip rate (15-25mm/yr), long quiescence (~325 years), and multiple single-event displacements of ~3 meters, make this portion of the fault potentially ready for a rupture (e.g. Fialko, 2006).
This southernmost San Andreas Fault site is extremely well suited to the recovery of event evidence, because the fault zone is distributed over 34 m in width, and the deformation has been recorded in a 10 m thick sequence of latest Holocene lacustrine sediments. The exposed stratigraphy spans about 1300 years and records at least six earthquakes. |
