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View South from Los Trancos Ridge

The Northern San Andreas Fault


The fault runs from near left to far right through Stevens Creek valley and other gaps in the Santa Cruz Mountains. (more below)
The little bend begins
Photo (c) 2007 Andrew Alden, licensed to About.com (fair use policy)
At this spot, the San Andreas fault begins to enter the "little bend" section as it enters the Santa Cruz Mountains. The flank of Black Mountain, whose wooded slopes overlook the Silicon Valley, is on the left edge. At center is the valley of Stevens Creek. On the left horizon is a cluster of peaks that loom over the city of San Jose: Mount Umunhum on the left and Loma Prieta on the right have structures on their tips that are visible in the full-size view.

The fault takes a subtle bend to the left through these mountains. In that orientation, the transcurrent motion along the fault exerts compression across it that has raised these mountains. In a right-lateral fault like the San Andreas, a left-stepping bend is known as a locking bend and a right-stepping bend is a releasing bend, which results in downdrop basins like the Carrizo Plain in the central segment and the Coachella Valley in the southern segment.

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