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Variable-period surface-wave magnitudes: A rapid and robust estimator of seismic moments

Bulletin of the Seismological Society of America

By:
, , and
DOI: 10.1785/0120090388

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Abstract

We demonstrate that surface-wave magnitudes (Ms), measured at local, regional, and teleseismic distances, can be used as a rapid and robust estimator of seismic moment magnitude (Mw). We used the Russell (2006) variable-period surface-wave magnitude formula, henceforth called Ms(VMAX), to estimate the Ms for 165 North American events with 3.2 <Mw < 6.5 at distances ranging from 48 to 5268 km. Of the 7370 event-station pairs, more than half (4051) of the measurements were at distances less than 1000 km. Mw estimated from broadband waveform modeling (Herrmann et al., 2008) were regressed against Ms(VMAX). Mw can be estimated from Ms (VMAX) using the relationship: Mw = 1.91 + 0.66Msx (VMAX) for 2 <Ms < 6. The observed scatter of the Mw[Ms(VMAX)] with respect to Mw[Waveform Modeling] was approximately ??0.2 magnitude units (m.u). The residuals between Mw [Ms(VMAX)] and Mw [Waveform Modeling] show a significant focal mechanism effect, especially when strike-slip events are compared with other mechanisms. Validation testing of this method suggests that Ms(VMAX)-predicted Mw's can be estimated within minutes after the origin of an event and are typically within ??0.2 m.u. of the final Mw[Waveform Modeling]. While Mw estimated from Ms(VMAX) has a slightly higher variance than waveform modeling results, it can be measured on the first short-period surface-wave observed at a local or near-regional distance seismic station after a preliminary epicentral location has been formed. Therefore, it may be used to make rapid measurements of Mw, which are needed by government agencies for early warning systems.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Variable-period surface-wave magnitudes: A rapid and robust estimator of seismic moments
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/0120090388
Volume
100
Issue:
5 A
Year Published:
2010
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of the Seismological Society of America
First page:
2301
Last page:
2309
Number of Pages:
9