Rotational motions in homogeneous anisotropic elastic media

Abstract

We study rotational motions in homogeneous anisotropic elastic media under the assumption of plane elastic wave propagation. The main goal is to investigate the possible use of collocated measurements of rotational and translational motions for extracting anisotropic properties. The focus is on P-waves that – theoretically – do not have a rotational component of motion in isotropic media. We develop relations for rotational motions of body waves as a function of propagation direction and elastic parameters using the Kelvin-Christoffel equation and the Thomson parameters, descriptive of the degree of anisotropy. We quantify amplitudes of rotation rates and radiation patterns and conclude that 1) amplitudes of quasi P rotation rates in transverse isotropic media depend on two Thomsen parameters \epsilon and \delta*; 2) for strong local earthquakes and typical reservoir situations quasi P rotation rates induced by anisotropic effects are significant, recordable, and can be used for inverse problems; 3) collocated point measurements of both translational and rotational motions of quasi P waves in transversely isotropic media allow, theoretically, the extraction of anisotropic parameters; and 4) for tele-seismic wave fields anisotropic effects are unlikely to be responsible for the observed rotational energy in the P-coda.

BibTeX
@article{id1406,
  author = {Pham, D. N. and Igel, H. and de la Puente, J. and K\"aser, M. and Schoenberg, M. A.},
  doi = {10.1190/1.3479489},
  journal = {Geophysics},
  language = {en},
  number = {5},
  pages = {D47{\textendash}D56},
  title = {Rotational motions in homogeneous anisotropic elastic media},
  volume = {75},
  year = {2010},
}
EndNote
%O Journal Article
%A Pham, D. N.
%A Igel, H.
%A de la Puente, J.
%A Käser, M.
%A Schoenberg, M. A.
%R 10.1190/1.3479489
%J Geophysics
%G en
%N 5
%P D47–D56
%T Rotational motions in homogeneous anisotropic elastic media
%V 75
%D 2010