DEFORMATION IN THE SANTA-BARBARA CHANNEL FROM GPS MEASUREMENTS 1987-1991

Geodesy is one of the few techniques that can be used to estimate strain rates across the submerged structures in the Santa Barbara Channel. By resolving relative surface velocities, the Global Positioning System (GPS) can be used to infer crustal deformation rates independent of geologic models. GPS measurements from the period 1987-1991 have been used to derive velocities for a 8 station network bounding the channel. These estimates are based on 10 GPS experiments each of several days in length over this 4.5 year period. Precision of individual determinations of intersite vectors range from 3 to 7 mm for the horizontal components and average 20 mm in the vertical. The GPS data indicate high rates of shortening in the eastern channel (6+/-1 mm/yr at N16+/-3E) and low rates of deformation in the western channel. Comparisons with previous geodetic studies suggest that deformation in the region has not been uniform over the last 100 years.