THE ROLE OF DIP-SLIP FAULTING IN VERTICAL-AXIS ROTATION KINEMATICS: EXAMPLES FROM SOUTHERN CALIFORNIA

A growing body of paleomagnetic and structural data from southern California indicates that the kinematics of vertical-axis rotation is dominated by dip-slip faulting. Early kinematic models that were heavily dependent on strike-slip faulting are not fully supported by field observations of fault kinematics and have been adjusted by later observations and tectonic reconstructions that show the necessity of dip-slip faulting. This is especially apparent along rotation boundaries where differential rotation is observed between rotated and nonrotated areas. I propose here that dip-slip faulting with variable amounts of displacement along strike is the dominant process by which rotation is accommodated in the brittle crust and that strike-slip faults do not contribute to differential rotation and do not define rotation boundaries. I synthesize new and previously published paleomagnetic and structural data from southern California that support this hypothesis. This ongoing refinement of rotation kinematics is crucial to our understanding of the tectonic development of southern California and the San Andreas fault system.