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Empirical site response and comparison with measured site conditions at ANSS sites in the Reno area

PANCHA, A., pancha@seismo.unr.edu; ANDERSON,J. G., jga@seismo.unr.edu; BIASI, G. glenn@seismo.unr.edu; ANOOSHEPOR, A., rasool@seismo.unr.edu; LOUIE, J. N., louie@seismo.unr.edu; Nevada Seismological Laboratory, University of Nevada, Reno, NV, 89557

The Advanced National Seismic System (ANSS) is an effort to modernize, expand, and integrate earthquake monitoring and notification in the United States. Key goals of ANSS include dense instrumentation in high risk urban areas to monitor and improve predictability of strong ground shaking, to provide emergency response personnel with real-time earthquake information, and to provide engineers data on the response of buildings and other structures. Western Nevada is one of the locations targeted by this effort. The cities of Reno and Sparks, Nevada, are located in a fault-controlled basin that is about 13 km wide and 21 km long. The small basin size and the growing Advanced National Seismic System (ANSS) accelerograph network within it makes this an ideal location for investigating the relationship between basin structure, near-surface geology, and ground motions. We evaluate site conditions at each of the ANSS strong motion stations in the Reno-Sparks area. Ground motions from local earthquakes are used to ascertain empirical site amplification effects within the basin using the soil to rock spectral ratio technique. A rock site, RFNV, located near the basin edge, is used as a reference site. The site response functions within the basin are mainly flat, but do show relative amplification, with some sites showing resonant peaks. These empirical site effects are compared with site conditions evaluated using average shallow shear wave velocities, measured using the refraction microtremor (ReMi) technique (Louie, 2001), in addition to local geological classifications. While the geology rock group has a lower mean amplification, the separation with those of the sedimentary groups not large. The Vs30 groups have distinct means that are well separated, indicating that velocity is a useful predictor of amplification.

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Last Modified: 2011 Aug 10

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