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Abstract

Earth’s rotation affects wave propagation to first order in the rotation through the Coriolisforce. The imprint of rotation on wave motion has been accounted for in normal mode theory.By extending the theory to propagating surface waves we account for the imprint of rotation asa function of propagation distance. We describe the change in phase velocity and polarization,and the mode conversion of surface waves by Earth’s rotation by extending the formalism ofKennett for surface wave mode conversion due to lateral heterogeneity to include the Coriolisforce. The wavenumber of Rayleigh waves is changed by Earth’s rotation and Rayleigh wavesacquire a transverse component. The wavenumber of Love waves in not affected by Earth’srotation, but Love waves acquire a small additional Rayleigh wave polarization. In contrast todifferent Rayleigh wave modes, different Love wave modes are not coupled by Earth’s rotation.We show that the backscattering of surface waves by Earth’s rotation is weak. The couplingbetween Rayleigh waves and Love waves is strong when the phase velocities of these modesare close. In that regime ofresonant coupling, Earth’s rotation causes the difference betweenthe Rayleigh wave and Love wave phase velocities that are coupled to increase through theprocess of level-repulsion.