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Unless otherwise noted, NS paths are used in this paper to mean those paths whose ray directions in the inner core are nearly parallel to (within 30°) Earth's spin axis, and EW paths are those whose ray directions in the inner core are nearly parallel (within 50°) to the equatorial plane.
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Here we assume that the attenuation anisotropy (with higher attenuation along NS paths) persists to great depth of the inner core, which also shows strong anisotropy in velocity (15). It is possible that the attenuation anisotropy changes with depth. Of the few models with strongest depth-dependent attenuation in the inner core [D. J. Doornbos, Geophys. J. R. Astron. Soc. 38, 397, (1974); G. L. Choy and V. F. Cormier, ibid. 72, 1 (1983)] we examined, we cannot account for the anomalous broadening at 151° and, at the same time, the lack of broadening at 173°.
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we examined, we cannot account for the anomalous broadening at 151° and, at the same time, the lack of broadening at 173°
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Here we assume that the attenuation anisotropy (with higher attenuation along NS paths) persists to great depth of the inner core, which also shows strong anisotropy in velocity (15). It is possible that the attenuation anisotropy changes with depth. Of the few models with strongest depth-dependent attenuation in the inner core [D. J. Doornbos, Geophys. J. R. Astron. Soc. 38, 397, (1974); G. L. Choy and V. F. Cormier, ibid. 72, 1 (1983)] we examined, we cannot account for the anomalous broadening at 151° and, at the same time, the lack of broadening at 173°.
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One example is an event in SSI on 26 December 1984 recorded at COL in Alaska [Fig. 4 in (17)].
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Supported by the National Science Foundation. This work would not be possible without open access to the IRIS Data Management Center and the German GEOFONE Data Center. We thank X. M. Ding, J. Cassidy, S. Malone, and R. Lester for assistance in data collection. Comments from two anonymous reviewers greatly improved the manuscript.
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