We present fault slip rate estimates for Southern California based on Global Positioning System (GPS) velocity data from the University NAVSTAR Consortium (UNAVCO), the Southern California Earthquake Center (SCEC), and new campaign GPS velocity data from the San Bernardino Mountains and vicinity. Fault slip-rates were calculated using Tdefnode, a program used to model elastic deformation within lithospheric blocks and slip on block bounding faults [2]. Our block model comprised most major faults within Southern California. Tdefnode produced similar slip rate values as 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) in the SW section of the San Andreas fault (SAF). The slip rate of the SAF 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. 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. We determine that the northwest and Southeast sections of the SAF are slipping fastest with slip being partitioned over several faults in the central model area. In addition, our modeling technique produces similar results to other geodetic studies but deviated from geologic estimates. We conclude that Tdefnode is a viable modeling technique in this context and at the undergraduate level.

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