Dynamic Rupture Simulations on the Pitas Point Fault: Addressing the Geometry Question
Julian C. LozosSubmitted September 7, 2025, SCEC Contribution #14818, 2025 SCEC Annual Meeting Poster #TBD
California‘s western Transverse Ranges have a long complex network of thrust faults, which accommodates transpression through the San Andreas system, uplifts the ranges themselves, and contributes significant seismic hazard to cities like Ventura and Santa Barbara. The Pitas Point Fault is just one in this network, but it is particularly notable in that it is the likely source fault for the damaging ˜M6.5 1925 Santa Barbara earthquake. The specific geometry of this fault is the subject of long-term debate, however, to the point where there are two interpretations in the SCEC Community Fault Model – one with two shallowly-dipping ramps connected by a nearly flat section, and one with a steeper, less-variable dip. Here, I use dynamic rupture simulations to test which version of the Pitas Point fault geometry produces model earthquakes that best match observed uplift patterns and stress drops, and geologically-inferred strong ground motions. I find that the ramp-flat-ramp geometry consistently produces a better match to the data than the steeper planar geometry does, regardless of initial stress amplitude or nucleation point. This suggests that this geometry should be continued to be treated as “preferred” within the SCEC CFM. It also informs how to consider the geometry of intersections between the Pitas Point and other nearby faults, which in turn may influence our assessment of plausible earthquake sizes and paths in the Santa Barbara-Ventura area.
Key Words
dynamic rupture modeling, earthquake simulations, Transverse Ranges, Ventura, Santa Barbara, Pitas Point Fault, fault geometry
Citation
Lozos, J. C. (2025, 09). Dynamic Rupture Simulations on the Pitas Point Fault: Addressing the Geometry Question. Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)