### 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
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Ru-Shan Wu
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*Inst. of Tectonics, Univ. of California, Santa Cruz, CA 95064
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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.]