Antipodal seismic observations of temporal and global variation at Earth's inner-outer core boundary

Abstract

We have found two pairs of earthquake doublets closely located antipodally on one diametral axis between Tonga-Algeria, and several other events on other axes. These doublets show significant correlation, and exhibit seismic phases traversing the Core that cannot be explained by a standard radial Earth model such as PREM. The antipodal waveform data are highly variable between axes. The observed variability of the waveforms indicates global variations in the structure above and below the Inner-Outer Core boundary region. We have found evidence for a regional low-velocity zone at the base of the Outer Core, corresponding with a decadal temporal variation (0.55 s) in seismic energy traversing the top of the Inner Core. We propose an antipodal seismic array to constrain and to provide further progress for the study of the Inner and Outer Core. Copyright © 2010 by the American Geophysical Union.