ELASTIC BLOCK MODELING OF FAULT SLIP RATES ACROSS SOUTHERN CALIFORNIA USING UPDATED GPS VELOCITY DATA FROM THE SAN BERNARDINO MOUNTAINS AND VICINITY

We present fault slip rate estimates for Southern California based on GPS velocity data from UNAVCO, SCEC, and new campaign GPS velocity data from the San Bernardino Mountains and vicinity. Fault slip-rates were calculated using Tdefnode, a Fortran program used to model elastic deformation within lithospheric blocks and slip on block bounding faults (McCaffrey, 2015). Our block model comprised most major faults within Southern California. Tdefnode produced relatively similar slip rate calculations as compared to other geodetic modeling techniques. The fastest slipping faults are the Imperial fault (37.4±0.1 mm/yr) and the Brawley seismic zone (23.5±0.1 mm/yr). The slip rate of the San Andreas fault decreases northwestward from 18.7±0.2 mm/yr in Coachella Valley to 6.6±0.2 mm/yr along the Banning/Garnet Hill sections, as slip transfers northward into the Eastern California Shear Zone (9.4±0.3 mm/yr on the Camprock-Emerson-Homestead Valley faults and 3.4±0.5 mm/yr on the Calico-Pisgah-Bullion-Mesquite Lake faults). Slip remains slow on the San Gorgonio Pass and San Bernardino Valley sections (5.6±0.2 mm/yr and 4.3±0.2 mm/yr, respectively). North of the junction with the San Jacinto fault (10.5±0.2 mm/yr), the San Andreas fault slip rate increases to 14.2±0.1 mm/yr in the Mojave section. Tdefnode slip rate estimates match well with geologic estimates for SAF (Coachella), SAF (San Gorgonio Pass), San Jacinto, Elsinore, and Whittier faults, but not so well for other faults. Our model improved on those of past SCEC interns and is another step in the use of the Tdefnode program as a viable modeling technique for undergraduate research studies.