Publication Date:
2015-08-01
Description:
The traditional M s : m b discrimination method is routinely used for distinguishing between earthquakes and explosions within dense networks, but there is a need to improve discrimination at smaller magnitudes; therefore, we need magnitude scales that can successfully be applied to data from sparse networks. We developed a unified Rayleigh- and Love-wave magnitude scale ( M s U) that is designed to maximize available information from single stations and then combine magnitude estimates into network averages. By combining Love- and Rayleigh-wave amplitudes, we minimize the effect of earthquake radiation patterns from sparse networks, thereby improving discrimination between earthquakes and explosions. M s U is built from M s ( V MAX ) ( Russell, 2006 ) and is calculated from Love and Rayleigh waves that are narrowband filtered and corrected for propagation and source effects at periods between 8 and 25 s to find filter bands of maximum energy propagation. The data are also corrected for censoring effects at the station level, because either Rayleigh or Love waves may be below the signal-to-noise ratio threshold at a given period. We applied M s U to 39 earthquakes (3.21〈 M w 〈5.08) located in the Yellow Sea and Korean Peninsula region, as well as to the three North Korean nuclear tests (4.1〈 m b 〈5.1). By using M s U: m b as a discriminant, there is an increase in the separation of small magnitude earthquakes and explosions in sparse networks and a significant reduction in outliers, as shown in the application from the Korean Peninsula. This research addresses the theory, methods, and capability of M s U as a discriminant. Online Material: Detailed spectral analysis and M s U censoring algorithm, and figures of filter specifications.
Print ISSN:
0037-1106
Electronic ISSN:
1943-3573
Topics:
Geosciences
,
Physics
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