New slip rate estimates for the creeping segment of the San Andreas fault, California

Abstract

New continuous and differential global positioning system (GPS) measurements of recent slip rates and 30 yr alignment-array offsets from the central creeping segment of the San Andreas fault yield a maximum right-lateral slip rate of 25 ± 1 mm/yr. This slip rate is 20% slower than the 30 mm/yr slip rate accepted for this segment of the fault and 35% slower than the 39 mm/yr slip rate predicted between the Sierra Nevada–Great Valley block and the Pacific plate. New continuous GPS measurements between pairs of sites that flank the creeping segment at intersite distances of 1.0 km and 70 km give relative fault-parallel slip rates of 28 ± 2 and 30 ± 2 mm/yr, respectively. These observations indicate that right-lateral deformation rates increase with distance from the fault. Possible explanations for the gradient observed in the geodetic data are elastic strain accumulation along the creeping segment or significant distributed deformation on off-fault structures.