page_title: Carrizo Plain
section_title: Wallace Creek
hierarchical_section_title: Carrizo Plain / Geography and geology / Wallace Creek
caption_attribution_description: English: This view of the Wallace Creek (offset stream) is of perhaps the most famous feature on the San Andreas Fault. As the stream continues to progressively erode into its channel, right-lateral motion along the San Andreas Fault has moved the downstream portion of the channel northward. Sediments cut by Wallace Creek were radiocarbon dated at about 3,700 years old, and the stream channel has been offset about 430 feet since then (Sieh and Wallace, 1987). Earthquake fault investigations in the Carrizo Plain show that as many streams in the park area display evidence of right-lateral slip. Offset from the 1857 earthquake was in the range of 30 feet; two earlier earthquakes had slip displacements of about 40.6 feet (sometime between 1540 to 1630 A.D.) and 36 feet possibly between 1120 and 1300 A.D. (Sieh and Wallace, 1987). Offset along the fault shows a relative rate of motion in the in the Carrizo Plain (between A.D. 1210 and A.D. 1857) has averaged in the range of about 1.3 inches (34 mm) per year (Liu-Zeng and others, 2006).
context_page_description: The Carrizo Plain across, in southeastern San Luis Obispo County, California, about 100 miles (160 km) northwest of Los Angeles. It contains the 246,812-acre (99,881 ha) Carrizo Plain National Monument, and it is the largest single native grassland remaining in California. It includes Painted Rock in the Carrizo Plain Rock Art Discontiguous District, which is listed on the National Register of Historic Places. In 2012 it was further designated a National Historic Landmark due to its archeological value. The San Andreas Fault occurs along the eastern edge of the Carrizo Plain at the western base of the Temblor Range.
context_section_description: Wallace Creek is a small stream, draining into Soda Lake, that remains dry most of the year.  It drains perpendicular to the San Andreas Fault, and the creek bed is currently offset by 425 ft (130 m) due to the movement of the fault.  About 23 ft (7 m) of the displacement was created during the 1857 Fort Tejon earthquake. The current segment began forming 3,700 years ago.  Sometime between 1540 and 1630 A.D., the creek was offset by about 40.6 feet (12.4 m) feet in an even larger earthquake.
  Two other older creek beds lie 1,560 and 1,310 ft (475 and 399 m) northwest along the San Andreas Fault.  The first creek bed was created around 13,000 years ago when climate change formed the creek on a large active alluvial fan.  The second bed was created about 11,000 years ago.
  The creek has been carefully studied by geologists to find a correlation between the offset and historical events, such as earthquakes, that have occurred along the San Andreas Fault.  Although Wallace Creek is not the only creek that has been offset by the San Andreas Fault, it is the most spectacular.
caption: Wallace Creek offset by the San Andreas Fault, by about 430 feet in the last 3700 years.
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