Relative excitation of surface waves by earthquakes and underground explosions

Abstract

The surface-wave magnitude (Ms) is used as the measure of the relative excitation of long-period waves by underground explosions and earthquakes in five distinct geographical and tectonic regions of the world: the western United States, the Aleutian-Kamchatka area, southern Algeria (presumed explosions), central Asia, and Novaya Zemlya. The Ms-versus-mb data indicate that the underground explosions generated smaller surface waves than earthquakes from the same region of comparable body-wave magnitudes (mb). For the events (mb >5) and regions studied, the most significant result is that it is possible to separate the earthquake and explosion populations on the basis of their surface-wave magnitudes if the events are analyzed on a regional basis. Theoretical considerations of the dimensions of the seismic source in space and time lead to Ms-versus-mb relationships that account for the general trend of the observational data. Further elucidation of the diagnostic capability awaits the extension of such studies to events of lower body-wave magnitudes (mb <4).