Project Abstract
|
Our research has involved a multi-disciplinary effort to characterize the activity and earthquake potential of a series of poorly understood blind-thrust faults that lie at the heart of a major transfer zone connecting some of the largest, fastest-slipping reverse faults in the Western Transverse Ranges (WTR). Specifically, we have investigated the Ventura, Southern San Cayetano, and Pitas Point faults, which link shortening accommodated by the San Cayetano fault in the east with active thrust faulting along the Red Mountain fault and other active structures in the Santa Barbara Channel to the west (Figure 1). The Ventura fault underlies the Ventura Avenue anticline, and is one of the fastest uplifting structures in southern California, rising at a rate of ∼5 mm/yr [Rockwell et al., 1988]. However, there was persistent disagreement about whether this structure posed a significant hazard, stemming from uncertainty about the fault geometry at depth. Our results suggest that the Ventura fault does extend to seismogenic depths and accommodates uplift of the Ventura Avenue anticline by fault-propagation folding. Our subsurface fault models, combined with uplift rates based on the terraces [Rockwell et al., 1988], imply that the fault may rupture in M 7.7 or larger multi-segment earthquakes with repeat times of about 1000 years. Thus, this fault represents a major seismic hazard. |
