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A pragmatic approach to adjusting early instrumental local magnitudes for seismic hazard assessments in Australia  


Authors / CoAuthors

Allen, T.I.

Abstract

Prior to the development of Australian-specific magnitude formulae, the 1935 magnitude corrections by Charles Richter – originally developed for southern California – was almost exclusively used to calculate earthquake magnitudes throughout Australia prior to the 1990s. Due to the difference in ground-motion attenuation between southern California and much of Australia, many historical earthquake magnitudes are likely to be overestimated in the Australian earthquake catalogue. A method has been developed that corrects local magnitudes using the difference between the original (inappropriate) magnitude corrections and the Australian-specific corrections at a distance determined by the nearest recording station likely to have recorded the earthquake. These corrections have reduced the rates of local magnitudes of 4.5 in the historical catalogue by about 30% since 1900, while the number of magnitude 5.0 earthquakes has reduced by about 60% in the same time period. The reduction in the number of moderate-to-large-magnitude earthquakes over the instrumental period yields long-term earthquake rates that are more consistent with present-day rates, since the development of Australian-specific magnitude formulae. The adjustment of historical earthquake magnitudes is important for seismic hazard assessments, which assume a Poisson distribution of earthquakes in space and time.

Product Type

document

eCat Id

140159

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Commonwealth of Australia (Geoscience Australia)  
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Keywords

theme.ANZRC Fields of Research.rdf
  • Seismology and Seismic ExplorationEarthquake EngineeringEARTH SCIENCESNatural Hazards
  • Published_External

Publication Date

2021-06-01T05:08:39

Creation Date

Security Constraints

Australian Government Security ClassificationSystem    

Classification - unclassified

Legal Constraints

Creative Commons Attribution 4.0 International Licence    

Access - license

Use - license

Status

completed

Purpose

External Publication

Maintenance Information

notPlanned

Topic Category

geoscientificInformation

Series Information

Journal of Seismology

Lineage

Not supplied.

Parent Information

Extents

[-44.00, -9.00, 112.00, 154.00]

Reference System

Spatial Resolution

Service Information

Associations

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