Accuracy of computed shear -wave polarizations and time delays in anisotropic sedimentary rock

Observations of shear-wave splitting in sedimentary rocks result from wave propagation through combinations of finely stratified layers and stress-aligned fluid-filled cracks/pores (Bush and Crampin, 1991). To interprete such observations, a theory which simulates the elastic properties of finely-layered cracked rock is required. Hudson (1991) proposes a theory whereby the overall properties of a finely-layered material containing cracks can be found by attributing the fine-layer anisotropy to a hypothetical distribution of cracks. In developing this theory, Hudson includes all 1st- and 2nd-order pertubation terms due to the crack and crack-crack interactions, and consistently omits higher-order terms in crack density. However, when combining crack- and fine-layer anisotropies, alternative expressions can be formulated without omitting the higher-order terms at this later stage.