This image shows all the basin and range faults. You can see the releasing bend in Baja California as the western edge of NA is shifted to the NW. This change may have reactivated extension in the Rockies and in the Rio Grande Rift. The oceanic ridge between the Farallon and Pacific plates was subducted beneath N.A. and the boundary between the Pacific and N.A. plates became right-lateral strike-slip ultimately leading to the formation of the San Andreas fault system and parallel faults across the ~500 km of western N.A. Remnants of the Farallon plate are present off northwest U.S. and southern Mexico. Courtesy of Prof. Burchfiel.