On the plate boundary forces that drive and resist Baja California motion

Abstract

The driving forces of microplate transport remain one of the major unknowns in plate tectonics. Our hypothesis postulates that the Baja California microplate is transported along the North America–Pacific plate boundary by partial coupling to the Pacific plate and low coupling to the North America plate. To test this idea, we use numerical modeling to examine the interplate coupling on a multiple-earthquake-cycle time scale along the Baja California–Pacific plate boundary and compare the modeled velocity field with the observed geodetic motion of the Baja California microplate. We find that when the strain can localize along a weak structure surrounding microplate (faults), high interplate coupling, produced by frictional tectonic stresses, can reproduce the observed kinematics of the Baja California microplate as seen from geodetic rigid-plate motions. We also find that the northward motion of Baja California can influence the fault slip partitioning of the major faults in the North America–Pacific plate boundary region north of Baja California.