The purpose of this study is to obtain a better understanding of the area and the intricate fault interactions of not only the faults comprising the San Gorgonio thrust fault but also of its neighboring faults in connection with the San Gorgonio thrust.Through this study, I hope to construct a narrative of the intricacies of the region’s fault geometry (What combination of fault dip and locking depth best make sense considering our current knowledge of the area? And what combination can best reproduce the GPS data that we have?) and of any possible slip transfer between the faults of the San Gorgonio Pass and the Banning/Garnet Hill faults (Which strand is more active? What could this mean in terms of slip propagation and limitations of such slip during a potential major earthquake in the near future?).
While there are currently many different methods to model such fault interactions, this study incorporates the use of elastic block modeling through MATLAB (Meade and Loveless, 2009). Elastic block modeling consists of breaking up the earth into crustal blocks, with intersecting faults providing the boundaries of these blocks. The method models interseismic GPS velocities as arising from a combination of long-term motion of the blocks and elastic strain accumulation due to locking of faults. Euler poles describe the motion of tectonic bodies on a surface of a sphere depending on the direction of motion and the orientation of the boundary. In this study, GPS data from Dr. Sally McGill’s most recent GPS campaign was incorporated in this project as a measure to best estimate the blocks’ euler pole locations. Models were run with different permutations on the test parameters (fault traces along the Banning fault vs. Garnet Hill fault, strike along a certain fault segment, dip, and locking depth) and then compared to determine which combination of factors best reproduced the GPS velocities.