The spectral compositions (bandwidth 0.4 to 4.5 Hz) of the P codas of 108 explosions and 225 earthquakes recorded at LASA are the basis of a technique by which all earthquakes studied are discriminated successfully from all Semipalatinsk explosions. Such complete separation is not achieved, however, for the full set of presumed Russian explosions. The lack of detectable change in frequency content of P signals in the distance range 30° to 90° suggests a very high Qp value for the central mantle. This result, together with the observed rate of amplitude decay for long-period S waves, implies Qs for the central mantle is high while Qs values for the crust-upper mantle and lower mantle are very low.

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