Stochastic ground-motion prediction equations for southeastern Australian earthquakes using updated source and attenuation
parameters
Dataset Identification:
Resource Abstract:
Stochastic finite-fault ground-motion prediction equations (GMPEs) are developed for the stable continental region of southeastern
Australia (SEA). The models are based on reinterpreted source and attenuation parameters for small-to-moderate magnitude local
earthquakes and a dataset augmented with ground-motion records from recent well-recorded moderate-magnitude earthquakes relative
to those used in prior studies (Allen et al., 2007). The models are applicable for median horizontal-component ground-motions
for earthquakes 4.0 <= MW <= 7.5 and at rupture distances less than 400 km. Careful analysis of well-constrained Brune stress
drops indicates a dependence on hypocentral depth. It is speculated that this is the effect of an increasing crustal stress
profile with depth. However, rather than a continuous increase, the change in stress drop appears to indicate a discrete step
near 10 km depth. Average Brune stress drops for SEA earthquakes shallower and deeper than 10 km are estimated to be 23 MPa
and 50 MPa, respectively. These stress parameters are subsequently input into the stochastic ground-motion simulations for
the development of two discrete GMPEs for shallow and deep events. The GMPEs developed estimate response spectral accelerations
similar to the Atkinson and Boore (2006) GMPE for eastern North America (ENA) at short rupture distances (less than approximately
100 km). However, owing to higher attenuation observed in the SEA crust (Allen and Atkinson, 2007), the SEA GMPEs estimate
lower ground-motions than ENA models at larger distances. These differences become most obvious at distances greater than
200 km. A correlation between measured near-surface shear-wave velocity (VS30) and the site-dependent diminution term (K0)
was developed from the limited data available to determine the average site condition to which the GMPEs are applicable. Assuming
the correlation holds, a VS30 of approximately 820 m/s is obtained assuming an average path-independent diminution term K0
of 0.006 s from SEA seismic stations. Consequently, the GMPE presented herein can be assumed to be appropriate for rock sites
of B to BC site class in the modified National Earthquake Hazards Reduction Program (Wills et al., 2000; Building Seismic
Safety Council, 2003) site classification scheme. The response spectral models are compared against moderate-magnitude (4.0
<= MW <= 5.3) earthquakes from eastern Australia. Overall the SEA GMPEs show low median residuals across the full range of
spectral period and distance. In contrast, ENA models tend to overestimate response spectra at larger distances. Because of
these differences, the present analysis justifies the need to develop Australian-specific GMPEs where ground-motion hazard
from a distant seismic source may become important.
Citation
Title Stochastic ground-motion prediction equations for southeastern Australian earthquakes using updated source and attenuation
parameters
Metadata standard for this record:
ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
standard version:
1.1
Metadata record identifier:
c12439e0-a255-5972-e044-00144fdd4fa6
Metadata record format is ISO19139-2 XML (MI_Metadata)