Evidence for Punctuated Lateral Fault Growth In Response to Structural Inheritance: Camarillo Fold Belt

D. E. De Vecchio
University of California, Santa Barbara, CA, [email protected]

The Camarillo Fold Belt (CFB) is composed of several south-verging anticlines, which comprise the western extent of the west-trending highly segmented Simi fault zone that extends from the northern Simi Valley to the city of Camarillo. Subsurface and surface geologic relations indicate that most of the faults in the CFB are reactivated Miocene transrotational faults that now accommodate some component of Quaternary transpressional deformation. Fault segment boundaries typically contain north-trending steeply dipping faults that locally are cross-cut by or cut east-trending reverse faults. Structural relief decreases from east to west across each successive north-trending fault. Fold axes within discrete structural domains plunge 10° to 20° west, are truncated at the cross-faults, and do not have axes that plunge eastward. In addition, GIS-based analysis and limited geochronology suggest westward younging of tectonic topography across north-trending faults. We interpret these relations to suggest that westward propagation of the fold belt and the zone of deformation occurred by punctuated lateral growth of the Simi fault due to the presence of north-trending faults. Given the polyphase deformational history of the western Transverse Ranges, structural inheritance and this style of deformation may be common in southern California. The interpretation that faults propagate by punctuated lateral growth has important implications for seismic hazard assessment, as it suggest that transverse faults may be capable of limiting the magnitude of seismic moment for a particular event.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009