The Tehacchapi trilateration network spans the intersection of the San Andreas nd Garlock faults in southern California in the ''Big Bend'' region of the San Andreas fault. Analysis of data from 1973-1983 shows strain differences between the northwest and southeast regions of the network and slip at depth on both faults. The Palmdale network, spanning the San Andreas fault entirely within the Tehachapi network, showed increases of about 1 μstrain in both east-west and north-south extension in late 1979. The Tehachapi strains also jumped at this time, but the magnitude of the increase was only about one third that of Palmdale. The principal strain rates for Tehachapi over the time interval 1973-1983 are &egr;˙1=0.08¿0.01 μstrain/yr and &egr;˙2=-0.12¿0.01 μstrain/yr, with the 1 axis directed N76¿E. Strains were also computed for two subregions. The principal strain rates for the southeast Tehachapi region are &egr;˙1=0.14¿0.02 μstrain/yr and &egr;˙2=-0.16¿0.02 μstrain/yr, with the 1 axis directed N73''E. This result differs significantly from the principal strain rates at Palmdale (&egr;˙1=0.21¿0.02 μstrain/yr &egr;˙2=0.17¿0.01 μstrain/yr, with the 1 axis directed N71¿E). For the northwest Tehachapi region, &egr;˙1=0.11¿0.02 μstrain/yr and &egr;˙2=-0.06¿0.02 μstrain/yr, with the 1 axis directed N93¿E. |