Open AccessWide‐band coupling of Earth's normal modes due to anisotropic inner core structure
Author(s) -
Irving J. C. E.,
Deuss A.,
Andrews J.
Publication year - 2008
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2008.03824.x
Subject(s) - seismogram , inner core , anisotropy , coupling (piping) , normal mode , core (optical fiber) , physics , mode (computer interface) , observable , mode coupling , quality (philosophy) , computational physics , geology , geophysics , optics , seismology , materials science , quantum mechanics , computer science , metallurgy , vibration , operating system
SUMMARY We investigate the importance of wide‐band coupling of normal modes due to inner core anisotropy. We compare four different seismic models of inner core anisotropy, which were obtained by others using the splitting of Earth's normal modes. These models have been developed using a self‐coupling (SC) approximation, which assumes that coupling between nearby modes through anisotropic inner core structure is negligible. We test the SC approximation by comparing the frequencies and quality factors of 90 inner core sensitive modes, computed for these models using either the SC approximation or full‐coupling (FC) among large groups of modes. We find significant shifts in the quality factors and frequencies for some modes. Groups of modes which significantly couple together are constructed for six target modes. These groups are model dependent and in some cases contain large numbers of modes. Synthetic seismograms are calculated to show that the difference between SC and FC is observable on the scale of seismograms and of the same order of magnitude as the difference between synthetic and observed seismograms. Thus, future models of inner core anisotropy should take cross‐coupling between large groups of modes into account.