Paleoseismologic evidence for large-magnitude (Mw≥7.5) earthquakes on the Ventura blind thrust fault: Implications for multi-fault ruptures in the Transverse Ranges of southern California
Lee J. McAuliffe, James F. Dolan, Edward J. Rhodes, Judith A. Hubbard, John H. Shaw, & Thomas L. PrattUnder Review 2015, SCEC Contribution #2076
Detailed analysis of continuously cored boreholes and cone penetrometer tests (CPTs), high-resolution seismic reflection data, and luminescence and 14C dates from Holocene strata folded above the tip of the Ventura blind thrust fault constrain the ages and displacements of the two most recent earthquakes. These two earthquakes, which are identified by a prominent surface fold scarp and a stratigraphic sequence that thickens across an older buried fold scarp, occurred after about 700-900 years ago (most recent folding event[s]) and between 3-5 ka (previous folding event(s)). Minimum uplift in these two scarp-forming events was ~6 m for the most recent earthquake(s) and ~4.5 meters for the previous event(s). Such large uplifts require large-magnitude earthquakes in the range of Mw7.5 to 8.0 that likely involve rupture of the Ventura fault together with other Transverse Ranges faults to the east and west. The proximity of this large reverse-fault system to major population centers, including the greater Los Angeles region, and the potential for tsunami generation during ruptures extending offshore along the western parts of the system, highlight the importance of understanding the complex behavior of these faults for probabilistic seismic hazard assessment.
Citation
McAuliffe, L. J., Dolan, J. F., Rhodes, E. J., Hubbard, J. A., Shaw, J. H., & Pratt, T. L. (2015). Paleoseismologic evidence for large-magnitude (Mw≥7.5) earthquakes on the Ventura blind thrust fault: Implications for multi-fault ruptures in the Transverse Ranges of southern California. Geosphere, (under review).
