Global Compilation of Deep Mantle Anisotropy Observations and Possible Correlation With Low Velocity Provinces

We compile and make publicly available a global digital database of body wave observations of seismic anisotropy in the D′′ layer, grouped using the method used to analyze deep mantle anisotropy. Using this database, we examine the global distribution of seismic anisotropy in the D′′ layer, evaluati...

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Veröffentlicht in:Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2023-10, Vol.24 (10), p.n/a
Hauptverfasser: Wolf, Jonathan, Long, Maureen D., Li, Mingming, Garnero, Edward
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Sprache:eng
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Zusammenfassung:We compile and make publicly available a global digital database of body wave observations of seismic anisotropy in the D′′ layer, grouped using the method used to analyze deep mantle anisotropy. Using this database, we examine the global distribution of seismic anisotropy in the D′′ layer, evaluating the question of whether seismic anisotropy is more likely to be located at the edges of the two large‐low velocity provinces (LLVPs) in Earth's mantle than elsewhere. We show that this hypothesis lacks statistical justification if we consider previously observed lowermost mantle anisotropy, although there are multiple factors that are difficult to account for quantitatively. One such factor is the global lowermost mantle ray coverage for different phases that are commonly used to detect deep mantle anisotropy in shear wave splitting studies. We find that the global ray coverage of the relevant seismic phases is highly uneven, with LLVP edges and their interiors less well‐sampled than the global average. Plain Language Summary Seismic waves caused by earthquakes sometimes travel at different speeds in different directions. This material property, called seismic anisotropy, indicates convective flow and deformation in the mantle and has been detected in the lowermost mantle. We compile a database of lowermost mantle anisotropy locations from the previously published literature. Previous studies have reported strong seismic anisotropy at the edges of large features with lower than average seismic velocities in Earth's mantle, called large‐low velocity provinces. Here, we test whether seismic anisotropy is also more likely at large‐low velocity province edges than elsewhere. Our statistical analysis of our database suggests that this may not be the case. This analysis, however, did not explicitly account for the fact that the number of seismic waves traveling through the lowermost mantle is different from region to region. Key Points We compile a global digital database of seismic anisotropy observations in the D′′ layer We compute the global ray coverage of different methods used to detect deep mantle anisotropy In the context of a global compilation, there is no preferential occurrence of seismic anisotropy at large‐low velocity province edges
ISSN:1525-2027
1525-2027
DOI:10.1029/2023GC011070