NORMAL MODES OF A ROTATING,ELLIPTICAL EARTH .2. NEAR-RESONANCE MULTIPLET COUPLING

Certain of the Earth's poloidal and toroidal elastic‐gravitational normal mode multiplets may be strongly coupled to another multiplet by the Earth's rotation and ellipticity of figure. This paper uses Rayleigh's variational principle to specify the selection rules for strong mode coupling and to examine the nature and effects of this mode coupling. It is found that some of the normal modes of a slowly rotating, slightly elliptical Earth model may consist of about half poloidal type motion and half toroidal type motion. This strong coupling can severely hinder the problem of proper mode identification and measurement of the angular frequencies of oscillation of the Earth's normal modes. Copyright © 1969, Wiley Blackwell. All rights reserved