CRUSTAL STRAIN NEAR THE BIG BEND OF THE SAN-ANDREAS FAULT - ANALYSIS OF THE LOS-PADRES-TEHACHAPI-TRILATERATION-NETWORKS, CALIFORNIA

In the region of the Los Padres-Tehachapi geodetic network, the San Andreas fault (SAF) changes its orientation by over 30° from N40°W, close to that predicted by plate motion for a transform boundary, to N73°W. The strain orientation near the SAF is consistent with right-lateral shear along the fault, with maximum shear rate of 0.38±0.01μrad/yr at N63°W. In contrast, away from the SAF the strain orientations on both sides of the fault are consistent with the plate motion direction, with maximum shear rate of 0.19±0.01μrad/yr at N44°W. The best fitting Garlock fault model had computed left-lateral slip rate of 11±2mm/yr below 10km. Buried left-lateral slip of 15±6mm/yr on the Big Pine fault, within the Western Transverse Ranges, provides significant reduction in line length residuals; however, deformation there may be more complicated than a single vertical fault. A subhorizontal detachment on the southern side of the SAF cannot be well constrained by these data. -from Authors