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Updated Procedures to MLa Estimation for Australian Earthquakes

Created 09/01/2026

Updated 09/01/2026

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The principal magnitude type calculated by Geoscience Australia’s National Earthquake Alerts Centre (NEAC) in real-time monitoring of Australian earthquakes is the Australian local magnitude (MLa). However, successive changes to seismic analysis systems and methods of pre-processing seismic waveforms over the years have led to changes in how MLa has been calculated. These changes in MLa estimation have led to biases for the Australian earthquake catalogue. The waveforms of 862 confirmed earthquakes between August 2023 – August 2024 were prefiltered to three high-pass corner frequencies (0.10 Hz, 0.50 Hz, and 0.75 Hz) from which the MLa was recalculated. Quality selection criteria were applied targeting signal-to-noise ratios, minimum number contributing stations and the maximum distance of stations.

The number of network MLa estimates that met the quality selection criteria increased with increasing high-pass corner filtering (445 earthquakes for the unfiltered MLa versus 695 for MLa filtered to 0.75 Hz), which is attributed to the improvement of the SNR where prefiltering dampens background noise. The removal of background noise also resulted in a predominant decrease in magnitude estimates. Although this study does not consider potential MLa biases due to the measurement of large amplitude Rg phases, the study does provide recommendations for waveform pre-processing for magnitude estimates in the future. The recommendations provide more robust and consistent MLa estimates that will be ingested into the national earthquake catalogue. This will yield improved earthquake rate estimates for seismic hazard assessments in Australia.

Presented at the 2025 Australian Earthquake Engineering Society (AEES) National Conference

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Additional Info

Field Value
Title Updated Procedures to MLa Estimation for Australian Earthquakes
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/f1455f86-eb9b-4261-9274-83395344d0ed
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 24/11/2025
Geospatial Coverage
Map data © OpenStreetMap contributors
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Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Updated Procedures to MLa Estimation for Australian Earthquakes". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/updated-procedures-to-mla-estimation-for-australian-earthquakes