Block rotation and termination of the Hosgri strike-slip fault, California, from three-dimensional map restoration

The Hosgri fault is located immediately offshore of south-central Californi a and is part of the transform boundary between the Pacific and North Ameri can plates. This fault terminates to the southeast into east-trending folds and reverse-separation faults of the western Transverse Ranges. Our new st ructure-contour maps of deformed horizons show a spatial relationship betwe en faulting and folding consistent with right-lateral slip. Restoration of these digital maps quantifies post-Miocene right-lateral slip across the so uthern Hosgri fault to be 3.5 km. This slip is absorbed by folding, thrust overlap, and clockwise vertical-axis rotation of elongate blocks between st rands of the fault. The restored part of a block located to the east has ro tated 8 degrees clockwise. Extrapolating this restored rotation to the 50 k m block length produces an estimate of 7 km of dextral shear for a total, i ncluding the 3.5 km fault slip, of 10.5 km of post-Miocene displacement. Ou r three-dimensional approach precludes interpretations for reverse slip on the Hosgri fault, and is not consistent with models for more than 80 km of late Cenozoic right-lateral fault slip.