HR: 1330h
AN: S22B-0459    [PDF]
TI: Frequency Dependent Lg Q Within the Continental United States
AU: * Erickson, D
EM: drericks@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics P.O. Box 3006 University of Wyoming, Laramie, WY 82071-3006 United States
AU: McNamara, D
EM: mcnamara@usgs.gov
AF: United States Geological Survey, 1711 Illinois, Golden, CO 80401
AU: Benz, H
EM: benz@usgs.gov
AF: United States Geological Survey, 1711 Illinois, Golden, CO 80401
AB: A frequency-dependent quality factor, Q(f), is determined for three previously unstudied and four previously studied tectonic regions across the continental United States by inverting Lg time-domain amplitudes. Broadband seismic stations record high frequency (0.5 to 16 Hz) energy to determine regional attenuation for Southern and Northern California, the Basin and Range Province, the Pacific Northwest, the Mountain States, Central United States, and the Northeast United States. The Pacific Northwest, Northern California, and the Mountain States regions are new regions where there are no previous Lg Q results. Lg Q is determined at each of the five full octave bands with center frequencies at 0.75, 1.0, 3.0, 6.0, and 12.0 by assuming a geometrical spreading exponent of 0.5 and inverting for Q and source and receiver terms. The frequency-dependent quality factor is often modeled in the form of $\eta$. A delete-j Jackknife resampling technique is utilized for error analysis. In general, active tectonic regions have a low Qo value and a high frequency dependent variable $\eta$, whereas stable regions have a high Qo term and a low value for $\eta$. Southern and Northern California, the Basin and Range Province, the Pacific Northwest, and the Mountain States are all tectonically active regions and have frequency-dependent functions of Q = 152($\pm$37) f $^{0.72}$ ($\pm$0.16), Q = 105($\pm$26) f $^{0.67}$ ($\pm$0.16), Q = 200($\pm$40) f $^{0.679}$ ($\pm$0.12), Q = 152($\pm$49) f $^{0.76}$ ($\pm$0.18), and Q = 166($\pm$37) f $^{0.61}$ ($\pm$0.14) respectively. The remaining two regions, Central U.S. and Northeastern U.S., fall into the stable tectonic region category and have frequency-dependent functions of Q = 640($\pm$225) f $^{0.344}$ ($\pm$0.22) and Q = 650($\pm$143) f $^{0.36}$ ($\pm$0.14) . Both scattering and intrinsic attenuation mechanisms are likely to play an equal role for the range of frequencies considered in this study.
DE: 7205 Continental crust (1242)
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting