Structure and Seismic Hazard of the Ventura Avenue Anticline and Ventura Fault, California: Prospect for Large, Multisegment Ruptures in the Western Transverse Ranges

• DOI: 10.1785/0120130125
• Publication Date: 2014-05-06T23:55:17Z
• Authors: J. Hubbard; J. H. Shaw; J. Dolan; T. L. Pratt; L. McAuliffe; T. K. Rockwell
• Keywords: Anticline; Aqueduct

The Ventura Avenue anticline is one of the fastest uplifting structures in southern California, rising at ∼5 mm=yr.We use well data and seismic reflection profiles to show that underlain by fault, which extends seismogenic depth.Fault offset increases with depth, implying a fault-propagation fold.A decrease uplift rate since ∼30 10 ka consistent fault breaking through surface time implies has recent dip-slip ∼4:4-6:9 mm=yr.To west, fold trend continues offshore as Pitas Point its associated hanging wall anticline.The Ventura-Pitas appears flatten about 7.5 km depth detachment, called Sisar decollement, then step down on blind thrust north.Other regional faults, including San Cayetano Red Mountain link this system depth.We suggest below km, these faults may form nearly continuous surface, posing threat large, multisegment earthquakes.Holocene marine terraces it grows discrete events 5-10 m uplift, latest event having occurred ∼800 years ago (Rockwell, 2011).Uplift large would require earthquakes (M w 7.7-8.1)involving entire Ventura/Pitas possibly more along strike, such fault.Because local geography geology, be significant ground shaking amplification tsunamis.Ventura (onshore) (offshore).Circles locations wells evidence an intersection (see Fig. 4 for names).Seismic profiles: (left) industry line VB1, (center) Evergreen/Hall Canyon, (right) Brookshire profile.The box hatch marks shows location 3D volume across Dos Cuadras structure; from dataset, we interpret through, beyond, region.The marked dashed line; oil fields structural are squares: VOF, Oil Field; ROF, Rincon COF, Carpineteria DCOF, Field.North anticline.Near trace new, previously unmapped call (SSCF), shown either eastward continuation Lion backthrust or north-dipping ramp.The color version figure available only electronic edition.