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Golden Gate Park on the western edge of the city of San Francisco. This area is underlain by loose dune sand which presents a potential liquefaction, or quicksand hazard during a quake.

Just offshore of Lake Merced is the probable epicenter area for the 1906 Earthquake. Proximity to the epicenter typically means higher values for the intensity of shaking.

The San Andreas goes out to sea at the far left near the bump on the coast at Mussel Rock.

The valley between San Bruno Mountain, on the right, and Sweeney Ridge, on the left, is a dropped fault block which was submerged until relatively recent geologic time.

Buildings in the low lying area are constructed on various softer sediments which are more hazardous during seismic shaking. Structures on the upland slopes have potential landslide problems.

Here the San Andreas cuts through the most heavily built-up area in its 900 mile trail through California.

Skyline College sits near the fault on the west side, or Pacific Plate. It is built mostly on hard volcanic rock.

San Francisco International Airport sits on bay mud on the North American Plate. It is expected to be heavily damaged in any significant quake.

Another branch of the fault splits off at the north end of the reservoir and travels through the San Francisco Jail site.

A linear shutter ridge can be seen near the point of the reservoir where another branch of the fault splits off and again trends northwesterly toward the campus of Skyline College.

San Andreas Lake, an artificial reservoir, is held back by an earth fill dam built in 1860. The 1906 trace of the San Andreas broke through the eastern abutment.

To the west of the fault is Sweeney Ridge, and the site of the discovery of San Francisco Bay in 1769 by the party of Gaspar de Portola. (This was also the year of the first recorded earthquake in California, by the same expedition.)

Building to the right sit on progressively softer materials as one approaches the edge of the bay.

The small branch of the fault which trends to the northwest is the San Mateo Fault, along which the creek has established its flow.

Crystal Springs Dam along San Mateo Creek. This old structure, built in 1890, may be a major problem if it fails during an quake. Some 30,000 people downstream are at risk of flooding.

Interstate 280 closely parallels the fault. A major bridge crosses the outflow of San Mateo Creek near the large dam.

Upper and Lower Crystal Springs Reservoirs separated by Highway 92. The lakes fill natural depressions, or sags, where crystal clear springs and persistent ponds formerly marked the trace of the fault.

Long linear valleys are characteristic of lateral slip faults. In this area there are relatively few structures and the fault is a complex of fractures nearly one-half mile wide.

Surface streams flowing east into the fault zone are frequently deflected to the right by faulting and right lateral ground distortion.

Note the difference in vegetation on the western side of the fault compared to the eastern. This is primarily the result of slight differences in rock types as well as groundwater effects.

The distinctive structure to the left is the two mile long Linear Accelerator at Stanford University. At its west end the town of Woodside is literally cut by the fault.

Photos provided by NASA.

Overview of the dangerous San Andreas Fault from the middle of the San Francisco Peninsula. Scroll up to fly toward San Francisco.

	Golden Gate Park on the western edge of the city of San Francisco. This area is underlain by loose dune sand which presents a potential liquefaction, or quicksand hazard during a quake. Just offshore of Lake Merced is the probable epicenter area for the 1906 Earthquake. Proximity to the epicenter typically means higher values for the intensity of shaking. The San Andreas goes out to sea at the far left near the bump on the coast at Mussel Rock.
	The valley between San Bruno Mountain, on the right, and Sweeney Ridge, on the left, is a dropped fault block which was submerged until relatively recent geologic time. Buildings in the low lying area are constructed on various softer sediments which are more hazardous during seismic shaking. Structures on the upland slopes have potential landslide problems. Here the San Andreas cuts through the most heavily built-up area in its 900 mile trail through California.
	Skyline College sits near the fault on the west side, or Pacific Plate. It is built mostly on hard volcanic rock. San Francisco International Airport sits on bay mud on the North American Plate. It is expected to be heavily damaged in any significant quake. Another branch of the fault splits off at the north end of the reservoir and travels through the San Francisco Jail site.
	A linear shutter ridge can be seen near the point of the reservoir where another branch of the fault splits off and again trends northwesterly toward the campus of Skyline College. San Andreas Lake, an artificial reservoir, is held back by an earth fill dam built in 1860. The 1906 trace of the San Andreas broke through the eastern abutment. To the west of the fault is Sweeney Ridge, and the site of the discovery of San Francisco Bay in 1769 by the party of Gaspar de Portola. (This was also the year of the first recorded earthquake in California, by the same expedition.)
	Building to the right sit on progressively softer materials as one approaches the edge of the bay. The small branch of the fault which trends to the northwest is the San Mateo Fault, along which the creek has established its flow. Crystal Springs Dam along San Mateo Creek. This old structure, built in 1890, may be a major problem if it fails during an quake. Some 30,000 people downstream are at risk of flooding.
	Interstate 280 closely parallels the fault. A major bridge crosses the outflow of San Mateo Creek near the large dam. Upper and Lower Crystal Springs Reservoirs separated by Highway 92. The lakes fill natural depressions, or sags, where crystal clear springs and persistent ponds formerly marked the trace of the fault. Long linear valleys are characteristic of lateral slip faults. In this area there are relatively few structures and the fault is a complex of fractures nearly one-half mile wide.
	Surface streams flowing east into the fault zone are frequently deflected to the right by faulting and right lateral ground distortion. Note the difference in vegetation on the western side of the fault compared to the eastern. This is primarily the result of slight differences in rock types as well as groundwater effects. The distinctive structure to the left is the two mile long Linear Accelerator at Stanford University. At its west end the town of Woodside is literally cut by the fault.
	Photos provided by NASA. Overview of the dangerous San Andreas Fault from the middle of the San Francisco Peninsula. Scroll up to fly toward San Francisco.