Power-law Distribution of Fault Slip-rates in Southern California

Abstract

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 demonstrate that in the southern California fault system, between the Pacific and North American plates, both geologically and geodetically constrained fault slip-rate catalogs obey a power-law frequency distribution. Using this empirically constrained scaling relationship we derive an analytic expression for the partitioning of potency accumulation rate, which determines the distribution and magnitude of slip localization. This 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 which is consistent with models of continental deformation which explicitly represent a large though finite number of deforming structures.