J. H. Rosenbaum
1308 Castle Ct., Houston, TX 77006
The assumption that the earth is made up of homogeneous elastic layers, which can exhibit transverse isotropy and moderate constant-Q attenuation, leads to an effective method of modeling the response from a point source into a long spread of seismometer stations [J. H. Rosenbaum, Geophysics 36, 1276--1277 (1971)]. A difficulty experienced by users of such programs is the necessity of furnishing consistent elastic constants and absorption values for the formations. An extension of the long-wavelength-equivalent-medium theory [G. E. Backus, J. Geophys. Res. 67, 4427--4440 (1962)] to the anelastic case has been used to derive default options, which require minimal information from the user, appear reasonable for many earth materials, and reduce to a proper description for the case of isotropy. A very simple earth model demonstrates that parasitic modes are excited and the computations may become unstable when anelastic model parameters violate stability conditions or are inconsistent. [Work done at Shell Development Co.]