ANALYSIS OF ASYMMETRIC MULTIPATHING WITH A GENERALIZATION OF THE DOUBLE-BEAM METHOD

An array method integrating source and receiver array beamforming is p resented. The method is a generalization of previous work (Kruger et a t, 1993) to independent variation of slowness and azimuth in both the source and the receiver array. Compared to the analysis capabilities o f a single array, the resolution is enhanced, and asymmetric scatterin g configurations and multipathing can be studied. The generalized doub le-beam method (DBM) is applied to a data set consisting of nuclear ex plosions detonated in Eastern Kazakhstan and recorded-at the Yellowkni fe array in Northern Canada. The multipathing found for PcP and PdP is interpreted in terms of lateral inhomogeneity in the lowermost mantle below Severnaya Zemlya. Indications for Rayleigh-to-P-wave scattering observed for the Shagan River and Degelen subsites of the former main test site of the USSR in Eastern Kazakhstan can be related to the str ucture in the vicinity of the two subsites.