HR: 0830h
AN: S11D-0331    [PDF]
TI: Shaking Hazard Predictors in the Reno, Nevada Area Basin
AU: * Scott, J B
EM: jscott@seismo.unr.edu
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Clark, M
EM: xv1100mc@aol.com
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Rennie, T W
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Pancha, A
EM: pancha@seismo.unr.edu
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Park, H
EM: hpark@unr.edu
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Purvance, M
EM: mdp@seismo.unr.edu
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AU: Louie, J N
EM: louie@seismo.unr.edu
AF: Nevada Seismological Laboratory, Dept. of Geological Sciences, University of Nevada, Reno, University of Nevada MS 174, Reno, NV 89557 United States
AB: We investigated several known and potential predictors of earthquake hazard in the Reno basin including: 1) refraction microtremor shear velocity averaged over 30 m depth (V30); 2) gravity-depth modeling; 3) surface geology and soil type; and 4) a precarious rock limit on maximum historic shaking. We combined the results of a V30 transect across 16 km of the basin performed in October and November, 2001 with a gravity-depth modeling study reported in 2000 to produce a shear-velocity model applicable to the shallow basin. The shallow shear-velocity transect was completed using our refraction microtremor method. Shallow shear velocity predicts earthquake ground motion amplification and potential hazard in similar alluvium-filled basins, and is the basis of site hazard classification under NEHRP-UBC provisions (BSSC, 1998). A geologic map-based classification of nearly all of our transect line would be NEHRP-D. Our measurements of V30 revealed that, in fact, most (82%) of the transect is classified NEHRP-C. No correlation of V30 with most mapped surface geology or agricultural soil type was found. A precarious rock site on the northwestern side of the basin placed a 0.5 g limit on historic shaking. Anomalous sediments having unusually high V30 were discovered filling a western sub-basin and will be the subject of further study. We conclude that: 1) The Reno basin has stiff Tertiary sediments underlying the surface at shallower depths than do other urban basins such as the Los Angeles basin. Weaker soils appear to occur east of downtown Reno in the broad floodplain of the Truckee River. 2) Surface geology is a poor predictor of V30 in the Reno basin. 3) Very large earthquakes have probably not occurred in the Reno area in geologically recent times.
DE: 7212 Earthquake ground motions and engineering
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting