Geodetic and Geologic Constraints on the Distribution of Fault Slip-Rates in Southern California

The spatial partitioning of deformation in the continental crust and, in particular, at plate boundary zones is determined by the distribution of fault slip-rates. Analytic and numerical models of strain accumulation in the elastic upper crust have been divided into those that parameterize faulting as localized on a finite length fault system comprised of relatively few fast slip-rate faults, or as distributed throughout a continuum of relatively slow slip-rate faults. We use both geodetic and geologic data to estimate the frequency distribution of fault slip rates, per unit length, between the Pacific and North American Plates in the southern California fault system. Using these empirically constrained scaling relationship we calculate the partitioning of potency accumulation rate, which determines the distribution and magnitude of slip localization. These model describes the kinematics of both micro-plate and continuum deformation models, and predicts that 97% of the deformation in Southern California is accommodated on faults slipping at >1 mm/yr.