Supplementary Figure 9

Supplementary Figure 9: Mode-by-mode improvements in fit

We monitor c2/N' for each individual toroidal or spheroidal mode, where N' denotes the number of splitting function coefficients for that mode. The modes are binned into 3 groups of equal size: green modes show the most improvement in fit, yellow modes are average, and red modes show the least improvement. See the supplementary table caption for an explanation of each model.

Supplementary Figure 9A

Illustration of mode-by-mode improvements in fit when going from starting model SKS12WM13 to model S6.

Fundamental spheroidal modes, which are sensitive to shear velocity structure in the mid and upper mantle, consistently show large improvements.

Note that the fit to these modes does not improve very much compared to the spheroidal modes.

Supplementary Figure 9B

Illustration of mode-by-mode improvements in fit when going from S6 to SP6.

Compared to (A), modes with low angular degree improve in fit when lateral variations in P velocity are added to the inversion. These modes, in particular on the fifth overtone branch, are generally more sensitive to P velocity structure.

The fundamental toroidal modes show large improvements in fit when independent lateral variations in P velocity are introduced. In model S6, the S velocity model is forced to accommodate P velocity variations as well as S heterogeneity in order to fit the spheroidal modes (many of which have strong sensitivity to P heterogeneity). On the other hand, model SP6 allows for independent variations in S and P velocity such that P sensitive modes no longer alias P structure into S structure. Hence the S model is available to fit the toroidal modes.

Supplementary Figure 9C

Illustration of mode-by-mode improvements in fit when going from SP6 to SPRD6.

The low degree, higher frequency spheroidal modes are most affected; these are the modes with significant sensitivity to density.

Density heterogeneity does not affect the fit to toroidal modes significantly, which is to be expected.


Supplementary Figure 8

Supplementary Figure 10

Index of Figures


Miaki Ishii, Department of Earth and Planetary Sciences, Harvard University, copyright ©1999, all rights reserved
Last modified: September 7, 1999