Improvements to regional explosion identification using attenuation models of the lithosphere

Regional P/S amplitudes have been recognized as an effective discriminant between earthquakes and explosions. While closely spaced events generally discriminate easily, the application of this technique to broad regions has been hampered by large variations in the amplitude of phases due to the attenuation of the crust and upper mantle. Making use of a recent P‐wave and S‐wave attenuation model of the lithosphere, we have found that correcting the events using our amplitude methodology significantly reduces the scattering in the earthquake population. We demonstrate an application of this technique to station NIL using broad‐area earthquakes and the 1998 Indian nuclear explosion using the Pn/Lg discriminant in the 1–2 Hz passband. We find that the explosion, which is lost in the scatter of the earthquakes in the uncorrected discriminant, clearly separates by correcting for attenuation structure. We see a similar reduction in scatter and separation for the Pn/Sn and Pg/Lg discriminants.