Structural Architecture of the Western Transverse Ranges and Potential for Large Earthquakes

Yuval Levy, & Thomas K. Rockwell

Published August 8, 2016, SCEC Contribution #6564, 2016 SCEC Annual Meeting Poster #082

Fold-and- thrust belts evolve over time, can produce large-scale faults and potentially accommodate large magnitude earthquakes. The thrust fronts of these structures typically form large fold structures in their hanging walls, and they tend to propagate forward over time to form new thrust fronts. In the Santa Barbara and Ventura region of the Western Transverse Ranges (WTR) of southern California, the Pitas Point Thrust is interpreted as the current thrust front structure, and spatially stable back thrusts accommodate deformation in the hanging wall block of the thrust sheet (More Ranch fault, Rincon Creek fault, other faults). In our work we constructed several cross-sections for the WTR, combining various sources of data and previous models suggested by others. We interpret the nearly continuous overturned Tertiary stratigraphy of the Santa Ynez Mountains as a large anticlinorium that formed as the first thrust front over the (mostly) blind San Cayetano thrust, and that the thrust front propagated south with time to the Red Mountain fault and eventually to the currently active thrust front, the southward-vergent Pitas Point-Ventura fault. We further suggest that the steep dip angle of the Red Mountain fault, as observed near the surface, is a result of northward rotation of the fault, which causes it to flexurally slip. The northward rotation is also responsible for continued folding to the north (Ayers Creek syncline) and back thrusting on the hanging wall of the Red Mountain fault (Arroyo Parida fault).

Key Words
Western Transverse Ranges, Pitas Point, Red Mountain, San Cayetano

Citation
Levy, Y., & Rockwell, T. K. (2016, 08). Structural Architecture of the Western Transverse Ranges and Potential for Large Earthquakes. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology