• journal_title：Bulletin of the Seismological Society of America
• Contributor：Matthew D. Purvance ; John G. Anderson
• Publisher：Seismological Society of America
• Date：2003-
• Format：text/html
• Language：en
• Identifier：10.1785/0120020065
• journal_abbrev：Bulletin of the Seismological Society of America
• issn：0037-1106
• volume：93
• issue：2
• firstpage：600
• section：Articles

d="p-1">The Fourier spectra of S waves on strong-motion accelerograms fall off rapidly at the highest frequencies. Anderson and Hough (d="xref-ref-7-1" class="xref-bibr">1984) suggested characterizing the high-frequency fall-off as A(f) ∼ exp(–πκf), defining the observed rate of fall-off, κ, as the spectral decay parameter. It has been proposed that variability in κ results from variable near-surface attenuation and that estimates of κ from small- to moderate-magnitude events apply to the largest earthquakes. No systematic investigation into the behavior of κ over a broad magnitude range has been previously undertaken. The Guerrero Accelerograph Array has recorded enough strong-motion data from earthquakes with magnitudes ranging from under 3.0 to 8.0 to achieve a high level of statistical significance. The records are chosen to minimize the influence of the corner frequency on the spectral shape, and the κ values are estimated from the high-frequency slopes alone. This study finds that the terms in the model κ = κ_site + κ_event reduce the misfit significantly, with the κ_site and κ_event contributing similarly to the total κ value. Evidence suggests that κ_event results primarily from source characteristics as opposed to propagation path effects. The absence of a statistically significant dependence of κ on epicentral distance is observed in the Guerrero region. Measuring κ over the frequency bands from 10 to 30 Hz and 10 to 45 Hz reveals increasing κ_event with magnitude. When κ is measured from 25 to 45 Hz, κ_event is not correlated with magnitude, although its role in error reduction remains significant. κ_event also varies systematically with focal mechanism: of all M ≥5.1 earthquakes with available focal mechanisms, κ_event is on average 4.5 msec less in normal-faulting earthquakes than in thrusting events.