Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Environmental and Engineering Geoscience

This Article Figures Only Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by dePOLO, C. M. Articles by WERLE, J. L. Search for Related Content GeoRef GeoRef Citation

Latest Quaternary Fault Movement along the Las Vegas Valley Fault System, Clark County, Nevada

¹ Nevada Bureau of Mines and Geology, University of Nevada, Reno, NV 89557
² American Geotechnical, 5764 Pacific Center Boulevard, Suite 112, San Diego, CA 92121
³ 2905 Autumn Haze Lane, Las Vegas, NV 89117
⁴ Converse Consultants, 731 Pilot Road, Suite H, Las Vegas, NV 89119

Several faults exposed in a 4- to 8-m-deep excavation in North Las Vegas exhibit evidence for two surface-faulting earthquakes that offset latest Pleistocene deposits and paleo-land surfaces about 2 to 3 m per event. These faults are secondary to a major trace of the Las Vegas Valley fault system. The rupture events, defined here as the most recent and penultimate events in the excavation, are expressed as fault displacements within, and buried by, a latest Pleistocene and Holocene stack of intercalated silt-rich and clay-rich deposits. Rapid, brittle faulting offset soft sediments that had the potential to deform plastically and formed a fault scarp 2 to 3 m high in weakly to moderately consolidated materials. A radiocarbon date from organic-rich soil at the surface offset by the most recent event indicates it occurred after about 14,500 ¹⁴C years before present. The penultimate event likely was a few hundred to a few thousand years before this date, based on our estimate of the time required for intervening sedimentation and lack of soils. Local earthquakes along the Las Vegas Valley fault system likely caused the sudden fault offsets because these are typical features created by earthquakes (e.g., brittle faulting, fault scarps, tectonic colluvium), and the faults are in line with and adjacent to a distinct main fault. The faults are encountered at 2- to 3-m depths, and the events are evident below this. Therefore, exploratory trenches in young sediments within Las Vegas Valley should be deeper than 3 m if the existence of latest Quaternary faulting is to be detected.

Key Words: Faults • Fault Exposure • Earthquakes • Las Vegas