Attenuation of Ground-Motion Spectral Amplitudes in Southeastern Australia

• DOI: 10.1785/0120060172
• Publication Date: 2007-08-01T16:12:52Z
• Authors: T. I. Allen; P. R. Cummins; T. Dhu; J. F. Schneider
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (sea). Events were recorded 1993 2004 range in size moment magnitude 2.0 ≤ M 4.7. The decay of vertical-component Fourier spectral amplitudes modeled by trilinear geometrical spreading. low- frequency can be approximated the coefficient R −1.3 (where hypocentral distance) within 90 km seismic source. From approximately 160 km, we observe transition zone which coda are affected postcritical reflections midcrustal Moho discontinuities. In this distance range, spreading +0.1 . Beyond low-frequency energy attenuates rapidly with source–receiver distance, having −1.6 associated seismic-quality factor expressed polynomial: log Q ( f ) = 3.66 − 1.44 + 0.768 (log 2 0.058 3 frequencies 0.78 19.9 Hz. amplitudes, corrected anelastic attenuation, regressed obtain quadratic source scaling coefficients. Modeled displacement spectra fit observed data well. Amplitude residuals are, on average, relatively small do not vary distance. Predicted (i.e., at 1 km) consistent eastern North American (ena) models low less than Hz) indicating that magnitudes calculated sea scales used ena over range. presented represent first prediction equations developed Australian region. This work provides useful framework development relations earthquake hazard risk assessment sea.