Seismological and geological settings of San Andreas Fault System (SAFS) in northern California. Color-shaded relief map and seismicity of the California margin from just north of Mendocino Triple Junction (MTJ) to the latitude of just south of Parkfield. Seismicity from 1967 to 2010 from the Northern California Earthquake Data Center (NCEDC 2012) shown as red dots for events smaller than M4 and orange open circles for larger events. A simplified trace of the main San Andreas Fault sensu strictu (SAFss) is shown. The seismicity itself marks the approximate locations of most of the other members of the seismologically active San Andreas Fault System between the Great Valley and the SAFss and active strands to the east and west of it. The fossil trench of the former Farallon : North America subduction system is taken from McCulloch (1987), dashed where interpolated. The strike-parallel and strike-normal purple lines represent the locations of geophysical cross sections corresponding to Figure 6 and Figure 7, respectively.