eprintid: 1357 rev_number: 14 eprint_status: archive userid: 2 dir: disk0/00/00/13/57 datestamp: 2015-02-23 10:44:56 lastmod: 2017-02-08 12:21:31 status_changed: 2015-04-27 12:10:45 type: article metadata_visibility: show creators_name: Allen, T. I. creators_name: Cummins, P. R. creators_name: Dhu, T. creators_name: Schneider, J. F. creators_id: tallen@usgs.gov creators_id: creators_id: creators_id: corp_creators: Geologic Hazards Team, U.S. Geological Survey, Golden, Colorado 80401 title: Attenuation of Ground-Motion Spectral Amplitudes in Southeastern Australia ispublished: pub subjects: MP3_2 divisions: EPOS-P full_text_status: none abstract: A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for south- eastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 <= M <= 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low- frequency spectral amplitudes can be approximated by the coefficient of R^(-1.3) (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypo- central distance range, geometrical spreading is approximately R^0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source–receiver distance, having a geometrical spreading coefficient of R^(-1.6). The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)^2 + 0.058 (log f)^3 for frequencies 0.78 <= f <= 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations developed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations for earthquake hazard and risk assessment in SEA. date: 2007-08 date_type: published publication: Bulletin of the Seismological Society of America volume: 97 number: 4 publisher: Seismological Society of America pagerange: 1279-1292 id_number: doi:10.1785/0120060172 refereed: TRUE issn: 0037-1106 official_url: http://dx.doi.org/10.1785/0120060172 access_IS-EPOS: limited owner: Publisher citation: Allen, T. I. and Cummins, P. R. and Dhu, T. and Schneider, J. F. (2007) Attenuation of Ground-Motion Spectral Amplitudes in Southeastern Australia. Bulletin of the Seismological Society of America, 97 (4). pp. 1279-1292. DOI: https://doi.org/10.1785/0120060172