Abstract

Since the 1960s, comparing a Rayleigh-wave magnitude Ms to the body-wave magnitude mb (Ms:mb) 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 (Ms:Ms). To calculate the magnitudes, we apply the time-domain magnitude technique called Ms(VMAX), 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 Ms(VMAX) obtained from Love waves is greater than that estimate from Rayleigh waves. Conversely, 79 of 82 nuclear explosions analyzed (96%) had network-averaged Ms(VMAX)-Rayleigh equal to or greater than the Ms(VMAX)-Love. We used logistic regression to examine an forumla 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 forumla versus Ms:mb using common data. We fully expect that forumla will contribute significantly to multivariate event identification.

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