Mantle flow models with core-mantle boundary constraints and chemical heterogeneities in the lowermost mantle

2008 ◽  
Vol 113 (B5) ◽  
Author(s):  
B. Steinberger ◽  
R. Holme
Keyword(s):  
Mantle Flow ◽  
Boundary Constraints ◽  
Flow Models ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
Lowermost Mantle

Application of spherical Slepian functions to the inversion of virtual observatory satellite magnetic data into localised regions of flow on the core-mantle boundary

2021 ◽  
Author(s):  
Hannah Rogers ◽  
Ciaran Beggan ◽  
Kathryn Whaler
Keyword(s):  
Spherical Surface ◽  
Surface Flow ◽  
Magnetic Data ◽  
Virtual Observatory ◽  
Core Surface ◽  
Flow Models ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Slepian Functions

<p>Spherical Slepian functions (or ‘Slepian functions’) are mathematical functions which can be used to decompose potential fields, as represented by spherical harmonics, into smaller regions covering part of a spherical surface. This allows a spatio-spectral trade-off between aliasing of the signal at the boundary edges while constraining it within a region of interest. While Slepian functions have previously been applied to geodetic and crustal magnetic data, this work further applies Slepian functions to flows on the core-mantle boundary. There are two main reasons for restricting flow models to certain parts of the core surface. Firstly, we have reason to believe that different dynamics operate in different parts of the core (such as under LLSVPs) while, secondly, the modelled flow is ambiguous over certain parts of the surface (when applying flow assumptions). Spherical Slepian functions retain many of the advantages of our usual flow description, concerning for example the boundary conditions it must satisfy, and allowing easy calculation of the power spectrum, although greater initial computational effort is required.</p><p><br>In this work, we apply Slepian functions to core flow models by directly inverting from satellite virtual observatory magnetic data into regions of interest. We successfully demonstrate the technique and current short comings by showing whole core surface flow models, flow within a chosen region, and its corresponding complement. Unwanted spatial leakage is generated at the region edges in the separated flows but to less of an extent than when using spherical Slepian functions on existing flow models. The limited spectral content we can infer for core flows is responsible for most, if not all, of this leakage. Therefore, we present ongoing investigations into the cause of this leakage, and to highlight considerations when applying Slepian functions to core surface flow modelling.</p>

Investigation of core–mantle boundary topography and lowermost mantle with P4KP waves

2015 ◽  
Vol 204 (2) ◽  
pp. 1060-1071 ◽  
Author(s):  
David Schlaphorst ◽  
Christine Thomas ◽  
Richard Holme ◽  
Rafael Abreu
Keyword(s):  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
Lowermost Mantle

scholarly journals Imaging the lowermost mantle (D″) and the core-mantle boundary withSKKScoda waves

2008 ◽  
Vol 175 (1) ◽  
pp. 103-115 ◽  
Author(s):  
Ping Wang ◽  
Maarten V. de Hoop ◽  
Robert D. van der Hilst
Keyword(s):  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Lowermost Mantle

The origin of short-period precursors to PKP

1975 ◽  
Vol 65 (3) ◽  
pp. 765-786
Author(s):  
C. Wright
Keyword(s):  
Wave Energy ◽  
Wave Train ◽  
Outer Core ◽  
Temporal Changes ◽  
P Wave ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Short Period ◽  
Lowermost Mantle

abstract An investigation of the origin of precursors to short-period PKP phases has been undertaken using 23 earthquakes recorded at the Yellowknife Array at distances between 123° and 143°. In particular, the pattern of slowness and azimuth changes with time has been examined for coherent bursts of energy occurring throughout the precursor wave train. These temporal changes demonstrate that the precursor energy is most satisfactorily explained by scattering from small inhomogeneities at the core-mantle boundary or in the lowermost mantle, both before P-wave energy enters the core and when it re-emerges into the mantle. Moreover, scattering before entry into the core seems to generate the larger amplitudes. The bulk of the data cannot be attributed to reflection or sharp upward refraction from velocity discontinuities within the lower part of the outer core, although there is some ambiguous evidence for a reflecting interface at a depth of about 4850 km.

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