Imperial Valley GPS Resurvey

Southern California has a unique geological heritage because it straddles two different tectonic plates, each moving in its own direction. The western portion of California Department of Transportation District 11 is located on the rapidly moving Pacific plate and the eastern portion is on the stable North American plate.

The boundary between these two plates is approximately 100 kilometers wide and consists of a zone of subparallel faults. This area is referred to as the San Andreas Fault Zone. Since GPS technology has become readily available and affordable, it has provided a way to precisely determine the movement of the earth's crust over time.

This map shows the location of precise survey stations and their respective displacement because of plate tectonics. The direction and velocity of displacement was obtained by calculating the difference in station coordinates between time epochs of 1991.35 and 2004.0. Station coordinates were produced from precisely measured baselines constrained to horizontal time dependent positioning.