Garnet Hill

Garnet Hill Fault

Garnet Hill trace (Source:

Garnet Hill trace (Source:

The Garnet Hill strand of the San Andreas fault is a north-dipping right lateral strike slip fault that evolves into an oblique reverse fault at the western end, towards the San Gorgonio Pass (Southern California Earthquake Data Center). Fault interactions between the Garnet Hill fault and those west of the Cottonwood Canyon are still obscure (Yule and Sieh 2003).

Both the Garnet fault and the Banning fault have roles to play behind the complex fault behavior of the San Gorgonio Pass. Both faults tend to exhibit more strike slip behavior farther away from the San Gorgonio Fault Zone, but naturally, as they get closer to the heart of the thrust fault, they tend to show more dip slip characteristics. Interestingly, this transition between strike slip and dip slip tendencies lies within the Cottonwood Canyon, an area located right in the middle of the San Gorgonio fault zone (Yule and Sieh 2003). However, because 1) the Garnet Hill strand runs alongside to the Banning fault and 2) both interact with the San Gorgonio thrust fault, the issue of which fault is more active and whether or not there is slip transfer between these faults is raised.

In this study, alternate block models were run, where a block boundary is traced along the San Gorgonio thrust fault and the Garnet Hill fault and another where a block boundary is traced along the San Gorgonio thrust fault and the Banning Fault. This page will focus on solely the Garnet Hill fault and the trials testing the variations among dip, locking depth and strike along this boundary.

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