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A number of Satellite Laser Ranging (SLR) sites in the southwest United States and Mexico, in operation for over ten years, have been supporting the global laser network measuring tectonic plate motion and providing information for studies of regional crustal deformation. Observations of the Laser Geodetic Satellite (LAGEOS) collected in 1994 by the transportable satellite laser ranging system, TLRS-4, at two sites on the Baja peninsula now provide the means to extend the network of fixed stations at Monument Peak and Otay Mountain in southern California and Mazatlan on mainland Mexico. After the third SLR occupation of Ensenada, it's estimated site motion exhibits nearly the full plate rate predicted by the NNR-NUVEL1A model for a location on the Pacific plate. At the southern tip of the Baja, the motion of Cabo San Lucas has an azimuth that is more westerly than that expected from Pacific modeled motion. This discrepancy in azimuth, in conjunction with the slower SLR recovered velocity for Mazatlan, results in an apparent 6 mm/yr faster spreading rate across the mouth of the Gulf of California than that predicted by the NUVEL-1A model. The velocities of the Monument Peak and Otay Mountain sites show the expected long-term difference from Pacific plate motion, due to their proximity to the San Andreas Fault system. |
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