We investigate the use of intermediate-period surface-wave magnitude, Ms, and high-frequency body-wave magnitude, mb, from regional mining explosions for event discrimination by using techniques originally intended for separating earthquakes from explosions with teleseismic observations. The actual values of Ms and mb suggest that the surface waves generated by long-duration mining explosions can make them appear earthquakelike. The data from the single anomalous shot indicate that if a significant part of the total explosives is simultaneously detonated the event will move into the explosion population.
Data for this study are taken from a portable broadband deployment in Wyoming recording mining explosions in the Powder River Basin and a broadband network currently deployed in northeast China. The magnitudes, Ms (vmax) and mb were estimated for five, kiloton-size mining explosions, four in Wyoming and one in QianAn, China.
The resulting network Ms:mb data were compared with data from a previous study that included earthquakes and contained single-fired explosions (Stevens and Day, 1985; Bonner et al., 2003). Although the previous studies mostly examined events larger than those in this study, the Wyoming and China mining events plot in the earthquake population. Data from the anomalous Wyoming event, a blast in which a failure of the timing system caused a large portion of the blast pattern to simultaneously detonate, plot in the explosion population with mb 4.4. The simultaneous detonation of a large portion of blast array increased the body-wave magnitude but had little effect on surface-wave magnitude.