Eastern Section Meeting

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Boundary Element Modeling of Fault Cored Anticlines and Associated Blind Thrusts in Central California

Abstract

Recent literature investigating active folding indicates that crustal-scale anticlines grow primarily through slip on underlying faults. Such studies use the geometry and uplift rates of active fault-related folds to infer fault slip rate based upon an assumed kinematic relationship between fault slip and particle motion in the surrounding crust. Our method focuses on the mechanics of deformation using a boundary element model of flexural slip folding called BEAFS (Boundary Element Analysis of Flexural Slip). In many cases, the shallow geometry (<5km) of natural folds are well constrained by subsurface data, however, the geometry of the causative blind thrust faults is often not well imaged. By comparing our numerical simulations with published subsurface and surface data on naturally occurring folds we can determine the extent to which various mechanisms control fold evolution. We present preliminary model results for the underlying faults at Kettleman Hills South Dome, Kettleman Hills North Dome, and Coalinga Anticline in the San Joaquin Valley of Central California. Blind thrust faults associated with actively growing anticlines pose a significant global seismic hazard. Thus, these anticlines are of particular interest as they are the sites of two recent earthquake events—a Mw=6.5 earthquake in 1983 at Coalinga and a Mw=6.1 in 1985 at Kettleman Hills North Dome. Once our final models are prepared we can then compare published earthquake data from these events to the parameters predicted by BEAFS.