Frequencydependent effects on travel times and waveforms of longperiod S waves: implications for the scale of mantle heterogeneity
Igel, H., and O. Gudmundsson (1997),
Frequencydependent effects on travel times and waveforms of longperiod S waves: implications for the scale of mantle heterogeneity,
Phys. Earth Plan. Int., 104(13), 229246.
 Abstract
 The spectral properties of uppermantle velocity perturbations are dominantly determined from regional and global tomographic models. In this paper we study frequencydependent effects of longperiod S and SS waves of SHtype through random uppermantle models with specified spectral properties. In particular, we investigate the information content of the power spectra of travel time perturbations as a function of model spectrum and frequency band. Wave propagation is simulated by a finitedifference (FD) approximation to the axisymmetric wave equation in spherical coordinates. For global models with cylindrical symmetry and constant angular increment Delta theta, the use of spherical coordinates leads to an effective lateral grid spacing (are length) decreasing with depth. This is contrary to the requirements of global models with low velocities at the top of the mantle, which necessitate a dense grid spacing at small depths and a wider grid spacing at the base of the mantle. We introduce a grid with depthdependent lateral grid spacing to overcome this inconsistency. Our main findings are that (1) the properties of spatial power spectra of travel time fluctuations are frequencydependent; (2) power spectra of models obtained from longperiod tomography may underestimate the: power at intermediate scales; (3) frequencydependent effects on the waveform are sensitive to the scales and amplitudes of perturbations present in the upper mantle.
 BibTeX

@article{id327,
author = {H. Igel and O. Gudmundsson},
journal = {Phys. Earth Plan. Int.},
number = {13},
pages = {229246},
title = {{Frequencydependent effects on travel times and waveforms of longperiod S waves: implications for the scale of mantle heterogeneity}},
volume = {104},
year = {1997},
language = {en},
}
 EndNote

%0 Journal Article
%A Igel, H.
%A Gudmundsson, O.
%D 1997
%N 13
%V 104
%J Phys. Earth Plan. Int.
%P 229246
%T Frequencydependent effects on travel times and waveforms of longperiod S waves: implications for the scale of mantle heterogeneity