Spherical-wave AVO modeling in elastic and anelastic media
Arnim B. Haase, Charles P. Ursenbach
The AVO-response of two-layer isotropic models for AVO-Classes 1 and 3 is investigated for P-waves and converted waves. Zoeppritz reflection coefflcients and the Weyl/ Sommerfeld-integral are utilized for the computations. Spherical wave results for RPP and RPS are compared with plane wave reflectivity. Depth dependence of spherical wave AVO is found to be strongest near critical angles of Class 1. There is some similarity between RPP and RPS for Class 1. Normalized Class 3 responses show no depth dependence. There is no similarity between RPP and RPS for Class 3.
Anelasticity modifies the AVO-response of two-layer isotropic models. When reflection amplitude losses due to attenuation are compensated for by unit reflectivity scaling, AVO-characteristics similar to the elastic situation are found. Q-factor dependence of spherical wave AVO is found to be strongest near critical angles of Class 1. This Q-dependence, to some degree, mimics depth dependence of elastic comparisons. Normalized spherical wave Class 3 responses show a mild Q-factor dependence for the highest attenuation levels modelled at QP1 = 100. Wavelet stretch of converted wave AVO reflection traces is observed in addition to a phase rotation of all anelastic trace examples when compared to the elastic situation.