Short-period, vertical-component records at the WWSSN station, Kabul for 13 earthquakes and 8 nuclear explosions occurring within a region of efficient propagation of Lg are examined to explore the possibility of using ratios of amplitudes in different group velocity windows as a discriminant. Each seismogram is divided into 10 windows with boundaries representing Pn and group velocities of 6.0, 5.0, 4.5, 4.0, 3.8, 3.6, 3.4, 3.2, 3.0, and 2.8 km/sec. The first three windows include crustal phases Pn, Pg, and Sn, respectively, whereas the six windows from 4.0 to 2.8 km/sec encompass the expected group velocity of higher mode Rayleigh waves that include Lg. The ratio of the maximum amplitude before the arrival of Sn to the maximum amplitude thereafter is significantly larger for explosions than for earthquakes and provides the largest separation between earthquake and explosion populations. Considerable separation is also shown by amplitude ratios Pn/Lg and Pn/Pg. Amplitude ratios based on earlier- and later-arriving Lg phases and the amplitude ratio Sn/Lg show insignificant discrimination. The ratio (maximum before Sn)/(maximum after Sn) is expected to be a useful regional discriminant for events in the Western USSR.

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