ASA 127th Meeting M.I.T. 1994 June 6-10

1aSA1. Scattering and attenuation of elastic wave by a viscoelastic cylinder. I. P-wave incident.

Yin-Bin Liu

Ru-Shan Wu

Inst. of Tectonics, Univ. of California, Santa Cruz, CA 95064

The analytical expressions for scattered and transmitted fields from a circular elastic cylinder with and without intrinsic attenuation caused by a normally incident plane P wave or a normally incident cylindrical P wave are derived. The corresponding acoustic cases are also given by letting the shear modulus either inside or outside the cylinder be equal to zero. In the Rayleigh wave scattering regime, the solution agrees with standard approximate solutions. Resonance scattering, radiation pattern, scattering cross section, and synthetic seismogram are calculated. For a given mode number m in some discrete frequencies, either scattered compressional or scattered shear waves vanish for a nonabsorbing cylinder, and the amplitudes of scattered compressional and shear waves are always nonzero for an absorbing cylinder. The sawtooth shapes of a scattering cross section that appear in a low-velocity nonabsorbing cylinder will disappear in the absorbing cylinder. The scattered fields are the superposition of the geometrically reflected waves and a series of surface waves that circumnavigate the cylinder azimuthally, the amplitudes of scattered compressional waves are much greater than those of scattered shear waves (ka>>1). [Work supported by NSF.]