Citation

Allen, T.I., 2012. Stochastic ground-motion prediction equations for southeastern Australian earthquakes using updated source and attenuation parameters. Record  2012/069. Geoscience Australia, Canberra.

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.
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Product Type/Sub Type

nonGeographicDataset - GA Publication - Record

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2012

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Record
geohazards
earthquakes
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

docx
pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

c12439e0-a255-5972-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2012-05-29

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays