A suite of 33 Asian earthquakes and 36 Central Asia and Novaya Zemlya underground explosions are used to define the minimum detection levels in terms of surface-wave and body-wave magnitudes and the discrimination thresholds of the M versus m discriminant for the Canadian seismograph network. Under low microseismic noise conditions surface-waves can be observed for earthquakes down to m 4.9 and explosions down to m 5.9 for the region near the central Asia test sites. For events above these magnitudes, the M versus m relationships provide reliable discrimination between earthquakes and explosions. Comparison with an intracontinental study leads to the conclusion that the discrimination threshold is limited by path effects and greater distances to events about m 1.0 larger near the Asian test sites than near the Nevada test site.

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