Horizontal Velocity Field in the San Francisco Bay Area

The horizontal velocity field in the San Francisco Bay area is constrained by continuous GPS (CGPS) and survey-mode GPS (SGPS) measurements. These velocities are almost parallel to the regional faults and decrease from west to east as one approaches the interior of the North American plate. While a gradual transition across the San Andreas Fault indicates that it is locked, the abrupt transition across the southern Hayward fault indicates that it is creeping. This is confirmed by creepmeter measurements across the Hayward fault.