EXAMINATION OF A SPECTRAL METHOD FOR MEASURING THE EFFECTS OF ANISOTROPY1

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Abstract
The most diagnostic effect of anisotropy on shear waves is shear‐wave splitting. This phenomenon creates a distinctive signature in the 3D particle motion. Methods to extract the effects of anisotropy from shear‐wave data attempt to measure details of this motion. Many techniques have been published recently which process the shear waves in the time or frequency domain. Here we examine the way in which information on the interference effects between the split shear waves is contained within the frequency domain, and suggest some criteria which may be used in future processing algorithms. The time‐delay between the split shear waves, and the polarization direction of the leading shear wave can be converted into easily measured features from analysis of the Fourier spectrum of the shear‐wave signal on each component of motion. These features arise in the spectral interference patterns which are formed by the interaction between the two closely‐spaced and similar waveforms. The interference patterns are interpreted for synthetic and observed seismogram data.