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San Mateo Peninsula Segment

The Northern San Andreas Fault


In this view south, the fault runs through these reservoirs and into the Santa Cruz Mountains as it takes a slight curve leftward. (more below)
San Mateo Peninsula Segment
South of Mussel Rock, the fault passes through Daly City and into watershed land. The highway is Interstate 280, a good drive for seeing and contemplating this part of the fault. Three small reservoirs, San Andreas (SAR) and Upper and Lower Crystal Springs (CSR), lie on the fault trace. The stout earthen dams holding back these reservoirs held firm in 1906 and are not considered major hazards. Beyond them, the fault begins to take a slight leftward bend as it runs behind Black Mountain (BM) and through the notch directly beyond. Loma Prieta (LP) gave its name to the 1989 earthquake because the greatest shaking occurred in the wooded highlands to its west.

The bend in the fault results in compression across it as the Pacific plate on the right side moves toward the viewer. This thickens the crust and raises the Santa Cruz Mountains. Similar ranges rise along fault bends in the central segment and the southern segment.

The next view is looking north at this same section from a point to the right of the "BM" mark.

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