Open AccessCoupling of torsional modes in the Earth
Author(s) -
Tanimoto Toshiro,
Bolt Bruce A.
Publication year - 1983
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1983.tb01871.x
Subject(s) - multiplet , coupling (piping) , eigenfunction , physics , earth (classical element) , range (aeronautics) , geophysics , normal mode , earth model , classical mechanics , computational physics , spectral line , quantum mechanics , materials science , eigenvalues and eigenvectors , mathematical physics , vibration , composite material , metallurgy
Summary. The effect of modal coupling is examined for torsional eigenvibrations of an anelastic earth with oceanic and continental structure. While a coupling effect is hard to observe in the eigenspectrum, some eigenfunctions show significant coupled energy into a secondary neighbouring multiplet. The deeper the heterogeneity, the greater the coupling. Also, stronger coupling is observed in an elastic earth model than in an anelastic model because the poles of the two modes in the complex s ‐plane are closer in the elastic case than in the anelastic case. The scatter of Q values in a multiplet is less than 5 per cent in our examples but, in extreme cases, strong coupling produces Q values that range between the two Q values for the average earth models. The result indicates that caution is needed in determining Q values for modes that interfere. The results strongly suggest that necessity of incorporating coupling effects in the formulation of inversion aimed at resolving heterogeneity in the Earth.