Go to Google Earth and search for "south san francisco california." Then pan due west to the ocean, then a bit north to Mussel Rock.
Mussel Rock is on the Pacific plate, and the beach is on the North American plate; between them, in the water, is the San Andreas fault.
The line running southeast is pretty obvious. The long skinny lake is Crystal Springs Reservoir, a subduction lake directly over the fault.
At the very tip end of the lake is the Pulgas Water Temple and the feeder sluce.
John