Strain localization along the San Andreas Fault: consequences for loading mechanisms

The orientation of the near-fault strain accumulation associated with the relative motion between the Pacific and North American plates is better predicted by the orientation of the local faulting than by the orientation of the regional plate motion. This observation follows from consideration of shear strain results from geodetic studies ranging from the Imperial Valley to Shelter Cove along the San Andreas fault system. This set of results includes calculations from regions where the faulting and plate motion are considerably oblique to each other. Both the localization of the strain associated with Pacific-North American motion and the orientation of the associated strain can be simply caused by failure of the lithosphere (as opposed to localization of plate driving forces). Two types of models for the rheology and geometry of lithospheric failure are discussed. Models with vertical geometries are favoured. -from Authors