Irregular recurrence of paleoearthquakes along the central Garlock fault near El Paso Peaks, California

[ 1] New investigations at the El Paso Peaks paleoseismic site have refined and extended the record of paleoearthquakes for the central Garlock fault. Event evidence, in the form of buried fissures, scarps, folds, and upward terminations, has allowed us to identify six well-resolved earthquakes, designated as events W, U, R, Q, K, and F, within the last similar to 7000 years. The exposures that we excavated did not reveal additional evidence for three poorly resolved events reported by McGill and Rockwell [ 1998]. Evidence for event Y, identified in the previous study, was reexamined and found not to be a paleoearthquake. Radiocarbon dates of detrital charcoal, combined with a method of interpolating the event ages with revised sedimentation rates, provide our preferred constraints on the timing of faulting events. The most recent surface-rupturing earthquake, event W, occurred between A. D. 1450 and 1640. The penultimate event U occurred between A. D. 675 and 950. Event R, which was unrecognized in the previous study, occurred between A. D. 250 and 475. Event Q occurred relatively shortly before event R, between A. D. 25 and 275. Event K occurred between 3340 and 2930 B. C. The oldest identified paleoearthquake, event F, occurred between 5300 and 4670 B. C. The event ages indicate that earthquake recurrence is highly irregular at the El Paso Peaks site, with individual preferred intervals ranging from as little as 215 years to as many as 3300 years. The irregular recurrence of surface-rupturing earthquakes along the central Garlock fault may be related to temporal and spatial clustering of earthquakes proposed for faults in the Eastern California Shear Zone.