GEODETIC MEASUREMENT OF TECTONIC DEFORMATION IN THE SANTA MARIA FOLD-AND-THRUST BELT, CALIFORNIA

We have analyzed geodetic observations to resolve tectonic deformation across the Santa Maria Fold and Thrust Belt, northwest of Santa Barbara, California. The maximum compressive strain is oriented N17°E ± 5°E, and the compressive strain rate in this direction is 0.13 ± 0.03 μ strain/yr. Under the assumption that the unresolved rotational component of the velocity field is zero, we estimate that the integrated rate of deformation across the basin is 7 ± 1 mm/yr oriented at N03°E ± 13°. This vector can be decomposed into 6 ± 2 mm/yr of crustal shortening on the general structural trend of N30°E and 3 ± 1 mm/yr of right-lateral shear across this axis. On the basis of these values and earthquake focal mechanisms in the area, we infer that the deformation occurs on northwest trending folds and thrusts within the belt. These results are consistent with the rate and direction of deformation across the central California Coast Ranges. -from Authors