Determination of Love- and Rayleigh-Wave Magnitudes for Earthquakes and Explosions

Abstract

Since the 1960s, comparing a Rayleigh-wave magnitude M s to the body-wave magnitude m b ( M s: m b) 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 ( M s: M s). To calculate the magnitudes, we apply the time-domain magnitude technique called M s(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 M s(VMAX) obtained from Love waves is greater than that estimate from Rayleigh waves. Conversely, 79 of 82 nuclear explosions analyzed (96%) had network-averaged M s(VMAX)-Rayleigh equal to or greater than the M s(VMAX)-Love. We used logistic regression to examine an ![Graphic][1] 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 ![Graphic][2] versus M s: m b using common data. We fully expect that ![Graphic][3] will contribute significantly to multivariate event identification. [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif [3]: /embed/inline-graphic-3.gif