Polarization properties of near‐field waves in homogeneous isotropic and anisotropic media: numerical modelling

Abstract

The paper deals with the polarization properties of complete body waves propagating in elastic, homogeneous, unbounded, isotropic and anisotropic media. The waves excited by a point dipole source and by a line dipole source in an isotropic medium are computed by the numerical integration of Green's function. The waves excited by a line dipole source in an anisotropic medium are modelled by the finite‐difference method. It is shown that complete radiation patterns of P‐ and S‐waves of the dipole source in isotropic as well as anisotropic media do not generally have nodal lines, and that P‐ and S‐waves are not generally polarized linearly, but quasi‐elliptically. The degree of ellipticity decreases with increasing ratio r/λ and depends on the azimuth. A significant value of ellipticity was observed in the vicinity of the far‐field nodal lines even for ratios r/λ≅ 10 and more. For an anisotropic medium in the vicinity of the source a difference was detected between the predominant polarization direction of complete waves and the far‐field polarization direction. Copyright © 1992, Wiley Blackwell. All rights reserved