The effect of a general aspherical perturbation on the free oscillations of the Earth

Abstract

summary. The Lagrangian governing the infinitesimal elastic‐gravitational oscillations of a completely general earth model with interior fluid—solid boundaries is given. Rayleigh's principle is then used to derive a formula for calculating the first‐order perturbations in the eigenfrequencies due to an arbitrary slight perturbation of a spherically symmetric, non‐rotating, isotropic starting model. The perturbations considered include rotation, asphericity, elastic anisotropy, and a deviatoric initial stress, as well as a change in the positions of both welded and fluid—solid boundaries. Copyright © 1978, Wiley Blackwell. All rights reserved