Stoneley mode splitting function coefficients
Earth's normal modes are split due to the rotation, ellipticity and 3D heterogeneity of the Earth. Observations of this splitting hence place important constraints on the lateral variations of seismic velocities and density.
Making use of a large data set of large magnitude earthquakes over the last few decades, we have focused on the elusive core-mantle boundary (CMB) Stoneley modes (Koelemeijer et al., GRL (2013)), which are confined to the solid-liquid interface of the CMB. The splitting functions of these modes are consistent with the observed patterns in traveltime residual maps of core-diffracted body wave phases. Therefore, they provide important constraints on the velocity and density structure of the lowermost mantle.
Splitting function measurements of fundamental modes 0S15-0S30 have also been obtained. These match independently constrained surface wave phase velocity maps both in amplitude and pattern (Koelemeijer (2014)).
| Download our splitting function measurements here: | |
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| cst-coef.dat: Contains splitting function coefficients of nine Stoneley modes, 16 fundamental modes and nine other mantle modes (format specified at the top of the file). | |
| modes_obs_latlon.zip: Splitting function values at 5x5 degrees spanning (-180,180) longitude and (-90,90) latitude for nine Stoneley modes, 16 fundamental modes and nine other mantle modes. | |
| modes_obs_pics.zip: Plots of splitting function measurements for nine Stoneley modes, 16 fundamental modes and nine other mantle modes. | |
| If you are using the Stoneley mode splitting function data set, please reference: | |
| Koelemeijer, P., Deuss, A. & J. Ritsema (2013). Observations of core-mantle boundary Stoneley modes, Geophysical Research Letters, 40 (11), 2557-2561, doi:10.1002/grl.50514. | |
| Whenever you use the higher order fundamental modes 0S27-0S30, please reference: | |
| Koelemeijer, P. (2014). Normal mode studies of long wavelength structures in Earth's lowermost mantle. PhD Thesis, University of Cambridge. |
Examples of (left) Stoneley mode splitting function observations and (right) predictions for mantle model S20RTS (right), measured up to spherical harmonic degree smax.