Determination of Love- and Rayleigh-Wave Magnitudes for Earthquakes and Explosions and Other Studies
Final rept. 12 Jun 2009-30 Sep 2012
WESTON GEOPHYSICAL CORP LEXINGTON MA
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Since the 1960s, comparing a Rayleigh-wave magnitude, Ms, to the body-wave magnitude, mb, e.g., Msmb has been a robust tool for the discrimination of earthquakes and explosions. In this article, we apply a Rayleigh-wave formula as is to Love waves and examine the possibilities for discrimination using only surface wave magnitudes e.g., MsMs. To calculate the magnitudes we apply the time-domain magnitude technique called MsVMAX developed by Russell 2006 to Rayleigh and Love waves from explosions and earthquakes. Our results indicate that for the majority of the earthquakes studied 75, the MsVMAX obtained from Love waves is greater than the estimate from Rayleigh waves. Conversely, 79 of 82 nuclear explosions analyzed 96 had network-averaged MsVMAX-Rayleigh equal to or greater than the MsVMAX-Love. We used logistic regression to examine an MsRayleighMsLove discriminant. Cross-validation analysis of the new discriminant correctly identifies 57 of 82 explosions and 246 of 264 earthquakes while misidentifying 22 explosions as earthquakes and 11 earthquakes as explosions. Further comparative research is planned for MsRayleighMsLove versus Msmb using common data. We fully expect that MsRayleighMsLove will contribute significantly to multivariate event identification.
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