SEARCH

SEARCH BY CITATION

Additional supporting information may be found in the online version of this article.

FilenameFormatSizeDescription
2013GL055689R.fs01.pdfPDF document982KSchematic representation of the phase velocity computation (at station 595). A) The discrete travel times are spatially located at their corresponding stations. B) The travel times are interpolated onto a 50 m X 50 m regular grid and the travel time surface is cropped at the distances where the measurements become too sparse. C) The spatial gradient of the travel time surface is computed to give an estimate of the local phase slowness. D) The discrete amplitude data are interpolated onto the same grid than the travel times and the Laplacian-of-the-amplitude term of Equation 1 is computed and removed from the gradient term to give E) the distribution of local phase velocity as the magnitude of the vectors and F) the distribution of the local direction of wave propagation (black arrows, only every 5th arrows are shown for the clarity of the figure) as the direction of the vectors. The background color of frame F) shows the difference between the local direction of wave propagation and the straight ray approximation between the central station and each point of the grid.
2013GL055689R.fs02.pdfPDF document291KA) 1psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with the Helmholtz equation. B) 1psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with average phase velocities.
2013GL055689R.fs03.pdfPDF document794KA) 3psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with the Helmholtz equation. B) 3psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with average phase velocities.
2013GL055689R.fs04.pdfPDF document348KA) 4psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with the Helmholtz equation. B) 4psi azimuthal anisotropy fast direction and amplitude map at 0.7 s measured with average phase velocities.
2013GL055689R.fs05.pdfPDF document160KAzimuthal distribution of the phase velocity at 0.7 s for the station 1390 measured with average phase velocities. The small blue dots are the average phase velocity measurements. The large red dots with error bars are the average phase velocity averaged over 20 degrees. The thick red curve is the best fits for the mean velocity, 1psi, 2psi, 3psi and 4psi azimuthal parameters for the averaged velocity measurements. The values of the fitted parameters are shown with the subscript ‘av’. For comparison, the gray dots show the Helmholtz tomography measurements, the black dots with error bars are the Helmholtz measurements averaged in 20 degrees bins and the black curve is the best fit for the mean velocity, 1psi, 2psi, 3psi and 4psi azimuthal parameters. The values of the fitted parameters are shown. Note that the phase velocity measurements are less scattered than for the Helmholtz approach. For the average phase velocity method, we need to solve for the initial phase ambiguity. To remove it, we force the linear regression of the measured travel-times vs inter-station distance to pass by the origin point (Distance, time) = (0,0) by removing the y-intercept value.
2013GL055689R.fs06.pdfPDF document94KDistributions of the A, B, C and D parameters (in percent). The number in each frame is the median value of each parameter (note that the C and D values are in average about twice smaller than the A and B parameters).

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.