This site hosts the current collection of "best estimate" structure coefficients
, cst, for mantle sensitive modes.
These coefficients are described in Masters et al.
(2000).
Unlike body wave travel time data, free oscillation frequency shifts are sensitive
to variations in density within the Earth and hence are important seismic data
to help us understand the dynamics of the Earth.
Structure coefficients are the coefficients of a
spherical harmonic expansion and describe the lateral variations in observed
shifts on the mean frequency of a mode. The map representation of structure
coefficients is a splitting function, F.
We use fully normalized spherical harmonics (Edmonds, 1960).
Fortran source code
to read the files, select a mode, and make a
5x5 degree map of the corresponding splitting function
References
Edmonds, A.R., 1960,
Angular Momentum in Quantum Mechanics, Princeton Univ. Press.
Masters, G., Laske, G. and Gilbert, F., 2000, Matrix autoregressive analysis of
free-oscillation coupling and splitting, Geophys. J. Int., 143, 478-489.
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Gabi Laske ( glaske@ucsd.edu)
example plots for spheroidal modes
postscript file
example plots for toroidal modes
postscript file