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Earthquake duration magnitudes in southeast Australia, accounting for site, seismograph and source

Created 16/10/2025

Updated 16/10/2025

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A new expression with superior consistency in the calculation of magnitude from earthquake coda duration has been developed. The need to take into consideration the site, the seismograph characteristics and the source has been investigated. The expression is valid for distances up to 1000 km in southeast Australia except where the source is located on some other major geological foundation, for example the Australian shield or the Tasman Sea. The expression takes the form: MD = p1 + p2(log(SDD))P3 + p4Re-p5R . MD is duration magnitude, and the parameters in the above expression are determined by regression based on local magnitude ML. Duration, D, is in seconds, R is the hypocentral distance in kilometres, and pn are parameters. Parameter p1 zeroes the function to give values similar to ML and accounts for the definition of duration; p2 and p3 give the shape of the variation with duration; and p4 and p5 give the variation with distance. SD is the duration site correction factor , which varies from site to site and can be easily determined by comparing particular site durations with average durations. If the network data are electronically recorded, the value of SD for all sites can be continually monitored and updated. Because of the different methods of estimating D for the analogue and digital seismographs, a value of the parameter p1 for each seismograph type is necessary. analogue MD = - 0.46 + 0.45(log(SDD))2.4 + 0.0045Re-0.002R . digital MD = - 0.20 + 0.45(log(SDD))2.4 + 0.0045Re-0.002R . The above expressions present the relationship between MD, D (measured to double the background level) and R in southeast Australia for magnitudes between MD 0 and 5 and for distances from a few km to 1000 km.

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Field Value
Title Earthquake duration magnitudes in southeast Australia, accounting for site, seismograph and source
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/640f4fe8-9571-4ec1-ab1e-b721b9ee91af
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        140.5,
        -40.0
      ],
      [
        150.0,
        -40.0
      ],
      [
        150.0,
        -34.0
      ],
      [
        140.5,
        -34.0
      ],
      [
        140.5,
        -40.0
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Earthquake duration magnitudes in southeast Australia, accounting for site, seismograph and source". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/earthquake-duration-magnitudes-in-southeast-australia-accounting-for-site-seismograph-and-sourc