San Andreas Transform Fault Zone

By Irene K.Nester

April 25, 2008

ES 767 Global Tectonics, Spring 2008

Image Gallery: Surface Features of the San Andreas Fault Zone

The images in this gallery depict some of the major features of the San Andreas fault zone that are visible at the Earth's surface, but is not all inclusive. The photographs are ordered from south to north along the fault zone. Click on the individual photos to enlarge.

Photograph by I. K. NesterPalmdale Road Cut

This road cut through the San Andreas fault zone is located on the eastern side of the Antelope Valley Freeway just north of Avenue S in Palmdale, California. It is oriented roughly perpendicular to the strike of the fault and exposes many features of the zone where the surface rupture occurred during the 1857 Fort Tejon earthquake. At this location the fault zone, which includes the main rupture and many smaller subparallel ruptures, is approximately 1.6 km wide.

Photograph by I. K. NesterSouthern End of Palmdale Road Cut

This is southern end of the road cut not visible in the previous photograph. The darker rock on the left is gypsiferous clay shale and the lighter rock on the right is arkosic sandstone, both of the Pliocene Anaverde formation. The two lithologies are seperated by a major fault (center of frame) subparallel to the main rupture. The main trace of the San Andreas fault zone runs between the southern end of the roadcut (at right) and the Palmdale reservoir (background). The reservoir is a sag pond that was enlarged by man after the 1857 rupture.

Photograph by I. K. NesterCentral Section of Palmdale Road Cut

Complex folds in layers of gypsiferous shale (dark) and interbedded gypsum (light) of the Anaverde formation are exposed in the central portion of the road cut. This area is at the axis of the assymetrical syncline exposed in the cut. The folds are crossed by a major fault (right center of frame) and several minor faults.

Radar Topography Images of Fault Zone

These perspective images were created using data from the NASA Shuttle Radar Topography Mission (SRTM). The fault zone is the linear feature in the center of both images. The first image is looking northwest along the fault trace in the vicinity of Palmdale, California. The body of water in center of the image is the Palmdale Reservior. The city of Palmdale is visible at the left center of the image. The second image is a view farther to the northwest along the fault zone. Visit the NASA Visible Earth web site (first image, second image) for a more detailed description.

Photograph by I. K. Nester Lake Elizabeth Sag Pond

Lake Elizabeth, a sag pond along the Mojave segment of the San Andreas fault zone approximately 32 km northwest of Palmdale, California. Sag ponds occur along the fault zone in areas where the surface has subsided due to divergence of the two sides of the strike slip fault. The fault zone runs through this valley from right (southeast) to left (northwest) in the photograph. Note houses on the surrounding hills for scale.

Photograph by I. K. Nester
Lake Hughes Sag Pond

Lake Hughes, a smaller sag pond located along the fault zone approximately 3 km northwest of Lake Elizabeth. The fault zone runs from right (southeast) to left (northwest). Note houses on the northeastern shore for scale.

Photograph by Robert E. Wallace, USGS
The San Andreas Fault on the Carrizo Plain

The Carrizo Plain is approximately 90 to 130 km southeast of Parkfield, near the center of the fault zone. Many offset stream channels cut though the scarp along the fault and are well preserved due to the plain's arid climate. One of the best known is Wallace Creek, where about 130 m of horizontal offset can be readily observed. This includes 9 m of offset resulting from the 1857 Fort Tejon earthquake. Visit this USGS web site for a virtual tour and additional photos of the Wallace Creek area.

Photograph by Herb Lingl, Aerial Archives
Crystal Springs Reservoir, San Francisco

The trace of the northern San Andreas fault zone is clearly visible in the center of this aerial photograph looking northwest across the San Francisco Bay Area. The Crystal Springs Reservoir (foreground) fills the linear valley along the fault zone. Point Reyes is visible in the background. Stock photograph from Aerial Archives, used with permission.

References | San Andreas Transform Fault Main Page

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