A kinematic model for the Rinconada fault system in central California based on structural analysis of en echelon folds and paleomagnetism

Deformation associated with the Rinconada fault, one of the major strands of the San Andreas fault system in central California, is accommodated by both discrete fault offset (∼18 km) and distributed off-fault deformation. En echelon folds adjacent to the Rinconada fault were studied in detail at two locations, near Williams Hill and Lake San Antonio, to characterize the magnitude and style of distributed deformation. The obliquity between fold hinges and the local strike of the fault was 27° and 14° at these two sites, respectively. Systematic outcrop-scale fault displacement measurements along roadcuts indicate that the maximum horizontal elongation occurs parallel to local fold hinges and ranges from 4 to 9%. d the orientation and stretch of fold hinges to construct a transpressional kinematic model for distributed deformation. This modeling suggests a 20–50° angle of oblique convergence, 5 km of fault-parallel wrench deformation, and 2–4 km of fault-perpendicular shortening. Between 3° and 16° of clockwise rotation is also predicted by our model. This rotation is independently confirmed by a 14 ± 7° vertical axis rotation from regional paleomagnetic analyses. Integrating the regional discrete and distributed components of deformation suggests that the Rinconada fault system is 80% strike-slip partitioned.