Earthquake Risk: Two Faults Exposed in Eastern Sierra Nevada

ScienceDaily (Sep. 28, 2011) — Excavated trenches reveal two faults that bound the eastern flank of the Sierra Nevada in Antelope Valley, California and the Carson Range in Reno, Nevada. Observations by researchers at University of Nevada, Reno, suggest new details about the active faulting of the area.

Fault scarps that vertically offset young alluvial fan deposits along the Antelope Valley fault suggest the most recent surface rupture was at least 14 miles (23 km) long. Radiocarbon dating of bulk soil samples suggests the most recent earthquake occurred approximately 1350 years ago and the penultimate earthquake almost 5000 years earlier (or

6250 years before present day). The trench along the Carson Range provides insufficient data to quantify an earthquake event history, though large offsets appear to happen infrequently. The fault dips at a very low angle, which could have significant meaning for the behavior of the fault and the severity of related ground motion.

The article, "Paleoseismic Trenches across the Sierra Nevada and Carson Range Fronts in Antelope Valley, California and Reno, Nevada," is authored by Alexandra Sarmiento, Steven Wesnousky and Jayne Bormann of University of Nevada, Reno.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Seismological Society of America, via EurekAlert!, a service of AAAS.

Seismological Society of America (2011, September 28). Earthquake risk: Two faults exposed in eastern Sierra Nevada. ScienceDaily. Retrieved September 30, 2011, from http://www.sciencedaily.com /releases/2011/09/110928142441.htm