THE MOST RECENT SLIP EVENT ON THE LENWOOD FAULT, EASTERN CALIFORNIA SHEAR ZONE

The Lenwood fault is one of a set of active dextral faults within the Eastern California Shear Zone. This fault is crossed by several utility corridors for electricity and natural gas. Faults of the Eastern California Shear Zone are thought to rupture in clusters of M7+ earthquakes. Here we investigate evidence for the most recent rupture event along the Lenwood Fault, determined from paleoseismology to have occurred about 1-2ky. Field measurements of offset gullies from Soggy Lake in the south, to Stoddard Valley in the north, indicate slip of 2 to 4m for the most recent event. Larger, multi-event offsets support similar amounts of slip in prior events, with net offsets near 7m and 9m. Measurements of the most recent slip for the youngest event vary along the fault: lowest (~2m) at the southern and northern ends, and higher in between, averaging 2.5m overall. Scarp preservation is similar along all portions of the fault, indicating that the most recent event probably ruptured over 70 km of fault length to produce a M7.2 earthquake, similar to the nearby 1992 Landers and 1999 Hector Mine events.