Abstract
The attenuation structure of the Earth's inner core, in combination with the velocity structure, provides much insight into its rheological and mineralogical properties. Here, we use a large data set of PKIKP/PKiKP amplitude ratios to derive attenuation models for the upper 100 km of the inner core, incorporating the effects of velocity models calculated using the same data set. We confirm that the upper inner core is hemispherical in attenuation, with stronger attenuation in the east hemisphere. We also observe, for the first time, a low attenuation upper layer of approximately 30 km thickness throughout the top of the inner core. Attenuation increases beneath this layer, and then gradually decreases going deeper into the inner core. Although the data appear to show attenuation anisotropy below 57.5 km depth in the west, we find that this can be explained by the velocity models alone, with no requirement for attenuation anisotropy in the upper inner core.
Original language | English |
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Pages (from-to) | 2005-2015 |
Number of pages | 11 |
Journal | Geophysical Journal International |
Volume | 195 |
Issue number | 3 |
DOIs | |
Publication status | Published - Dec 2013 |
Funding
The research was funded by the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant 204995. AD is also funded by a Leverhulme Prize. LW is funded by a research fellowship from Homerton College, University of Cambridge. We thank two anonymous reviewers for helpful and constructive comments.
Keywords
- Core
- outer core and inner core
- Body waves
- Seismic anisotropy
- Seismic attenuation
- DEPTH-DEPENDENT ATTENUATION
- PKIKP TRAVEL-TIMES
- SEISMIC ATTENUATION
- PKP DATA
- ANISOTROPY
- HETEROGENEITY
- CONSTRAINTS
- BOUNDARY
- TOP
- TRANSITION