Surface-wave propagation in an ocean basin with an anisotropic upper mantle: numerical modelling

Abstract

Summary. The characteristics of surface-wave propagation in ocean basins are examined numerically for models with two types of anisotropic alignment in the upper mantle: one resulting from glide-plane slip in olivine with horizontal or vertical slip-planes, and the other from syntectonic recrystallization of olivine in a zone of horizontal shear. Glide-plane slip can cause highly anomalous inclined-Rayleigh particle-motion in the third-generalized mode (corresponding to the isotropic second-Rayleigh mode). The amplitude of this anomaly is rather insensitive to details of the structure. Syntectonic recrystallization can cause an anomalous combination of inclined-and tilted-Rayleigh motion in all modes. The variation with period of the amplitude of the anomaly in the fundamental mode can indicate the approximate depth to the anisotropic layer. In both types of alignment, the sense of tilt and the inclination varies with direction of propagation in a manner characteristic of the structural symmetry.