Paleoseismologic evidence for an early to mid-Holocene age of the most recent surface rupture on the Hollywood fault, Los Angeles, California

Examination of 11 adjacent, large-diameter boreholes reveals evidence for a t least one, and possibly two surface ruptures on the Hollywood fault durin g the past similar to 22,000 years. Bulk-soil radiocarbon ages recovered fr om a faulted, buried soil at 7-8 m depth, and overlying unfaulted alluvial units indicate that the most recent surface rupture occurred during early t o mid-Holocene time, between similar to 6,000 and 11,000 years ago, with a preferred time span of similar to 7,000 to similar to 9,500 years ago. Less well-constrained evidence for at least one separate, inferred fault splay that may cut an older buried soil, but not the youngest faulted soil, impli es the occurrence of at least one earlier surface rupture between similar t o 10,000 and similar to 22,000 years ago. These data suggest a very long re currence interval for the fault and confirm that the Hollywood fault is act ive and capable of producing damaging earthquakes large enough to cause sur face rupture beneath the northern edge of the densely urbanized Los Angeles basin. Comparison with published paleoseismologic data from the Santa Moni ca fault, along strike to the west, suggests that these faults, although th ey are part of the same oblique reverse-left-lateral fault system, probably did not rupture together during the most recent Hollywood fault surface ru pture.