San Andreas Fault Bends Bridge in Calif.
The San Andreas Fault bends the ParkfieldCoalinga Road Bridge over... News Photo 157917781Bending,Bridge,California,Creek,Fault,Road,Science and Technology,Small,USA,VerticalPhotographer Gary AveyCollection: Moment Copyright 2004 Gary D. AveyThe San Andreas Fault bends the Parkfield-Coalinga Road Bridge over Little Cholame Creek (Bridge No. 44C-0141)in Parkfield, California. This is a photo of the Parkfield-Coalinga Road Bridge over Little Cholame Creek (Bridge No. 44C-0141) just outside of the tiny town of Parkfield, California, the self professed 'earthquake capital of the world'. The bridge was built to cross Little Cholame Creek, but also happens to straddle the San Andreas Fault. Movement of the San Andreas Fault has caused the bridge to bend as demonstrated by the curve in the guard rail. This photo was taken about two weeks after the 6.0 Magnitude Parkfield Earthquake that occurred on September 28, 2004. Though the bridge had been retrofitted, you can see evidence in the curve of the guardrail and the angle of the bridge deck that the fault had displaced (bent) the bridge a total of about 8-12 inches. Measurements taken by numerous agencies indicated that the 2004 quake caused only about 1/2-inch to 1-inch of the surface displacement here, so the balance occurred due to fault creep (slow movement) before and/or after the quake. The San Andreas Fault passes under the bridge, perpendicular to the alignment of this southwesterly directed photo. The land on the near (east) side of the bridge is on the North American tectonic plate. The land on the opposite (west) side of the bridge is on the Pacific tectonic plate. The San Andreas is classified as a right-lateral strike-slip fault. The tectonic plate on the opposite side of the fault moves to the right in relation to the viewer as demonstrated by the movement of the guardrail and bridge deck on the opposite side of the fault in this photo.