Changes in Seismic Anisotropy After Volcanic Eruptions: Evidence from Mount Ruapehu V. Miller and M. Savage

Supplementary Material

The method to find used in this study was developed by Silver and Chan (20). The method uses a grid search to find the values of and t between the split phases that best correct the seismogram for the effects of anisotropy and returns the waveform into the linear form expected for an isotropic case. We subjectively grade the events based on the signal-to-noise ratio, the quality of the removal of anisotropy, the fit of the waveform once the t has been removed, the linearity of the particle waveform once the t has been removed compared to the ellipticity of the motion prior to remova,l and the confidence level contours around the best fit.

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Supplemental Figure 1. (A) Example waveform for a shallow event recorded during the 1994 deployment, in the initial N, E, and vertical reference frame. (B) The same waveforms in the horizontal plane, rotated into the initial polarization, i.e., the polarization determined (20) to have been the S-wave polarization before the wave entered the anisotropic medium, and the orthogonal direction. Waveforms are shown before and after correction for the splitting. Predicted S-wave arrival is denoted by Sb, while the window used in the measurement is given by T1 (start) and F (end).

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Supplemental Figure 2, 4, 6, and 8 (A) The waveform rotated into fast and slow directions. (B) This same waveform adjusted for t. (C) The particle motion plot that corresponds to the waveform rotated into fast and slow directions. (D) The particle motion plot that corresponds to the waveform corrected for t. (E) A contour plot showing the confidence level of the result. On this diagram the best fit is marked as a star and the 95% confidence level is highlighted with a double contour.

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Supplemental Figure 3. (A and B) Example waveform for a shallow event recorded during the 1998 deployment. See caption for Web Fig. 1 for notation.

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Supplemental Figure 5. (A and B) Example waveform for a deep event recorded during the 1994 deployment. See caption for Web Fig. 1 for notation.

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Supplemental Figure 7. (A and B) Example waveform for a deep event recorded during the 1998 deployment. See caption for Web Fig. 1 for notation.

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