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The Russell surface-wave magnitude formula, developed in Part I of this two-part article, and the M s (VMAX) measurement technique, discussed in this article, provide a new method for estimating variable-period surface-wave magnitudes at regional and teleseismic distances. The M s (VMAX) measurement method consists of applying Butterworth bandpass filters to data at center periods between 8 and 25 sec. The filters are designed to help remove the effects of nondispersed Airy phases at regional and teleseismic distances. We search for the maximum amplitude in all of the variable-period bands and then use the Russell formula to calculate a surface-wave magnitude.In this companion article, we demonstrate the capabilities of the method by using applications to three different datasets. The first application utilizes a dataset that consists of large earthquakes in the Mediterranean region. The results indicate that the M s (VMAX) technique provides regional and teleseismic surface-wave magnitude estimates that are in general agreement except for a small distance dependence of ‫200.0מ‬ magnitude units per degree. We also find that the M s (VMAX) estimates are less than 0.1 magnitude unit different than those from other formulas applied at teleseismic distances such as Rezapour and Pearce (1998) and Vanȇk et al. (1962).In the second and third applications of the method, we demonstrate that measurements of M s (VMAX) versus m b provide adequate separation of the explosion and earthquake populations at the Nevada and Lop Nor Test Sites. At the Nevada Test Site, our technique resulted in the misclassification of two earthquakes in the explosion population. We also determined that the new technique reduces the scatter in the magnitude estimates by 25% when compared with our previous studies using a calibrated regional magnitude formula. For the Lop Nor Test Site, we had no misclassified explosions or earthquakes; however, the data were less comprehensive.A preliminary analysis of Eurasian earthquake and explosion data suggest that similar slopes are obtained for observed M s (VMAX) versus m b data with m b Ͻ5. Thus the data are not converging at lower magnitudes. These results suggest that the discrimination of explosions from earthquakes can be achieved at lower magnitudes using the Russell (2006) formula and the M s (VMAX) measurement technique.

Surface waves were generated by the North Korean nuclear explosion of 9 October 2006 and were recorded at epicentral distances up to 34°, from which we estimated a surface wave magnitude (M s ) of 2.94 with an interstation standard deviation of 0.17 magnitude units. The International Data Center estimated a body-wave magnitude (m b ) of 4.1. This is the only explosion we have analyzed that was not easily screened as an explosion based on the differences between the M s and m b estimates. Additionally, this M s predicts a yield, based on empirical M s =yield relationships, that is almost an order of magnitude larger than the 0.5-1 kt reported for this explosion. We investigate how emplacement medium effects on surface wave moment and magnitude may have contributed to the yield discrepancy.

Surface wave magnitude (M s ) estimation for small events recorded at near-regional distances will often require a magnitude scale designed for Rayleigh waves with periods less than 10 sec. We have examined the performance of applying two previously published M s scales on 7-sec Rayleigh waves recorded at distances less than 500 km. First, we modified the Marshall and Basham (1972) M s scale, originally defined for periods greater than 10 sec, to estimate surface wave magnitudes for short-period Rayleigh waves from earthquakes and explosions on or near the Nevada Test Site. We refer to this modification as , and we have useds short-period, high-quality dispersion curves to determine empirical path corrections for the 7-sec Rayleigh waves. We have also examined the performance of the Rezapour and Pearce (1998) formula, developed using theoretical distance corrections and surface wave observations with periods greater than 10 sec, for 7-sec Rayleigh s is possible to employ a near-regional single-station or sparse network to estimate surface wave magnitudes, thus allowing quantification of the size of both small earthquakes and explosions. Finally, we used a jackknife technique to determine the falsealarm rates for the -m b discriminant for this region and found that the prob-s ability of misclassifying an earthquake as an explosion is 10%, while the probability of classifying an explosion as an earthquake was determined to be 1.2%. The misclassification probabilities are slightly higher for the estimates. Our future R‫ם‬P M (7) s research will be aimed at examining the transportability of these methods.