SEARCHING FOR MICROEARTHQUAKES ON DETACHMENT FAULTS BENEATH DEATH VALLEY, CALIFORNIA

A system of normal faults on the west edge of the Black Mountains is expressed as steeply dipping scarps and gently dipping detachments. Slip on the detachment faults has resulted in exhumation of the famous turtlebacks, the local term for the core complexes exposed in their footwalls. Geologic evidence shows that slip occurred on the detachments in late Quaternary time while they were gently dipping. We hypothesize that the detachment faults are active; alternatively, high-angle faults cut the detachments and Holocene slip has deactivated them. In order to test these hypotheses, we deployed a network of ten temporary seismic monitoring stations on the fans and in lower canyons along the eastern flank of the Panamint Range. Preliminary analysis of the first eleven months of data from our complete network reveals that more than 150 earthquakes originated in the shallow crust beneath the network. These earthquakes had coda duration magnitudes (Md) ranging from about - 0.5 to +2. Although we have not yet completed the analyses, the preliminary results are consistent with shallow active faulting distributed beneath both the bedrock in the Panamint Range and the bajada on its eastern flank.