Investigators at GNS Science Discuss Findings in Geology (A Depth-dependent Local Magnitude Scale for New Zealand Earthquakes Consistent With Moment Magnitude)

2021 APR 30 (NewsRx) -- By a News Reporter-Staff News Editor at NewsRx Science Daily -- Current study results on Geology have been published. According to news reporting originating in Lower Hutt, New Zealand, by NewsRx journalists, research stated, “A new reference attenuation model for calculating local magnitude (M-L) for New Zealand earthquakes is derived. An earlier reference model, denoted NZ16, was developed in 2016 as a possible alternative to the classical reference model used by GeoNet for earthquakes located by the SeisComP processing system since January 2012.”

Financial support for this research came from Strategic Science Investment Fund.

The news reporters obtained a quote from the research from GNS Science, “It aimed to provide a logA(0) attenuation relation of the amplitude with the hypocentral distance applicable to the New Zealand region and to make ML more consistent with moment magnitude (M-w). For the present update, denoted NZ20, a much larger set of regional moment tensor solutions and corresponding station amplitudes is available. Residual analysis is used to screen the individual station amplitude readings and then to exclude observations from periods of time when the station residuals were consistently anomalous. Effects of other possible sources of bias on the attenuation relation are also examined, including unreliable locations of earthquakes with large azimuthal gaps and the saturation of ML in large earthquakes. An extra explanatory variable is added to the attenuation relation to account for dependence on hypocentral depth, so the updated local magnitude is consistent with M-w across the full range of depths at which earthquakes occur in New Zealand. Furthermore, to counteract possible sources of bias, the data set for analysis is restricted.”

According to the news reporters, the research concluded: “Earthquakes above the approximate amplitude saturation threshold of M-w 6.6, as well as those with azimuthal gaps greater than 270 degrees, are excluded.”

This research has been peer-reviewed.

For more information on this research see: A Depth-dependent Local Magnitude Scale for New Zealand Earthquakes Consistent With Moment Magnitude. Bulletin of the Seismological Society of America, 2021;111(2):1056-1066. Bulletin of the Seismological Society of America can be contacted at: Seismological Soc Amer, 400 Evelyn Ave, Suite 201, Albany, CA 94706-1375, USA.

Our news correspondents report that additional information may be obtained by contacting David A. Rhoades, GNS Science, Lower Hutt, New Zealand. Additional authors for this research include Annemarie Christophersen, Sandra Bourguignon, John Ristau and Jerome Salichon.

The direct object identifier (DOI) for that additional information is: https://doi.org/10.1785/0120200252. This DOI is a link to an online electronic document that is either free or for purchase, and can be your direct source for a journal article and its citation.

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