HR: 12:05h
AN: S22B-07    [Abstracts]
TI: Evidence for Variability in the Shape, not Just the Level, in the High Frequency Spectrum of Strong Ground Motions
AU: * Anderson, J G
EM: jga@seismo.unr.edu
AF: Nevada Seismological Laboratory, Nevada Seismological Laboratory/174 University of Nevada, Reno, NV 89557 United States
AU: Biasi, G
EM: glenn@seismo.unr.edu
AF: Nevada Seismological Laboratory, Nevada Seismological Laboratory/174 University of Nevada, Reno, NV 89557 United States
AU: Brune, J N
EM: brune@seismo.unr.edu
AF: Nevada Seismological Laboratory, Nevada Seismological Laboratory/174 University of Nevada, Reno, NV 89557 United States
AU: Purvance, M D
EM: mdp@seismo.unr.edu
AF: Nevada Seismological Laboratory, Nevada Seismological Laboratory/174 University of Nevada, Reno, NV 89557 United States
AU: Kilb, D
EM: dkilb@epicenter.ucsd.edu
AF: Scripps Institution of Oceanography, IGPP 0225 UCSD, La Jolla, CA 92093-0225 United States
AB: The high-frequency spectrum of ground motions in Guerrero, Mexico and in Nevada and California has been examined from the perspective of the parameter "kappa". The main feature of the high frequency spectrum (i.e. above the corner frequency) can be approximated as proportional to exp(-pi*kappa*f). Based on a distance dependence, Anderson and Hough (1984) considered that kappa is a path effect related to Q. An alternative explanation is that it is predominantly affected by the seismic source. More recent studies indicate that both explanations are partially correct. In Mexico, Purvance and Anderson (2003) found that source and site terms have similar effectiveness in explaining and reducing the variability for multiple measurements. Similarly, in southern Nevada, the variability in kappa is reduced nearly as far as possible by a model with only site and event terms. The source contribution is an interesting phenomenon. In the simple omega-squared source model, the acceleration spectrum is flat above the corner frequency, although the level depends on stress drop. These results indicate that the shape also is variable. At least some of the shape variations above the corner depend systematically on event location and/or mechanism.
DE: 7223 Seismic hazard assessment and prediction
DE: 7203 Body wave propagation
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting