Empirical transfer functions: Application to determination of outermost core velocity structure using SmKS phases
Article first published online: 30 NOV 2007
Copyright 2007 by the American Geophysical Union.
Geophysical Research Letters
Volume 34, Issue 22, November 2007
How to Cite
2007), Empirical transfer functions: Application to determination of outermost core velocity structure using SmKS phases, Geophys. Res. Lett., 34, L22317, doi:10.1029/2007GL031932., and (
- Issue published online: 30 NOV 2007
- Article first published online: 30 NOV 2007
- Manuscript Accepted: 19 OCT 2007
- Manuscript Revised: 9 OCT 2007
- Manuscript Received: 5 SEP 2007
- outer core;
- whispering gallery mode;
- Wiener deconvolution
 SmKS waves provide good resolution of outer-core velocity structure, but are affected by heterogeneity in the D″ region. We have developed an Empirical Transfer Function (ETF) technique that transforms a reference pulse (here, SmKS) into a target waveform (SKKS) by: (1) time-windowing the respective pulses, (2) applying Wiener deconvolution, and (3) convolving the output with a Gaussian waveform. Common source and path effects are implicitly removed by this process. We combine ETFs from 446 broadband seismograms to produce a global stack, from which S3KS-SKKS differential time can be measured accurately. As a result of stacking, the scatter in our measurements (0.43 s) is much less than the 1.29 s scatter in previous compilations. Although our data do not uniquely constrain outermost core velocities, we show that the fit of most standard models can be improved by perturbing the outermost core velocity. Our best-fitting model is formed using IASP91 with PREM-like velocity at the top of the core.