Three-dimensional modelling convection in the earth's mantle: Influence of the core-mantle boundary

1990 ◽  
Vol 34 (3) ◽  
pp. 278-283 ◽  
Author(s):  
O. Čadek ◽  
C. Matyska
Keyword(s):  
Three Dimensional ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Earth’S Mantle

scholarly journals Sequencing seismograms: A panoptic view of scattering in the core-mantle boundary region

Science ◽  
2020 ◽  
Vol 368 (6496) ◽  
pp. 1223-1228 ◽  
Author(s):  
D. Kim ◽  
V. Lekić ◽  
B. Ménard ◽  
D. Baron ◽  
M. Taghizadeh-Popp
Keyword(s):  
Seismic Waves ◽  
Learning Algorithm ◽  
Three Dimensional ◽  
Boundary Region ◽  
Marquesas Islands ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
Subsurface Structures ◽  
The Core ◽  
The Pacific

Scattering of seismic waves can reveal subsurface structures but usually in a piecemeal way focused on specific target areas. We used a manifold learning algorithm called “the Sequencer” to simultaneously analyze thousands of seismograms of waves diffracting along the core-mantle boundary and obtain a panoptic view of scattering across the Pacific region. In nearly half of the diffracting waveforms, we detected seismic waves scattered by three-dimensional structures near the core-mantle boundary. The prevalence of these scattered arrivals shows that the region hosts pervasive lateral heterogeneity. Our analysis revealed loud signals due to a plume root beneath Hawaii and a previously unrecognized ultralow-velocity zone beneath the Marquesas Islands. These observations illustrate how approaches flexible enough to detect robust patterns with little to no user supervision can reveal distinctive insights into the deep Earth.

Improving Stoneley-mode constraints on the structures near the core-mantle boundary

2020 ◽  
Author(s):  
Harry Matchette-Downes ◽  
Robert D. van der Hilst ◽  
Jingchen Ye ◽  
Jia Shi ◽  
Jiayuan Han ◽  
...  
Keyword(s):  
Material Properties ◽  
Three Dimensional ◽  
Normal Modes ◽  
Shear Velocity ◽  
Boundary Region ◽  
Earth Model ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Special Cases

<p>Although observations of seismic normal modes provide constraints on the structure of the entire Earth, the core-mantle boundary region remains poorly understood. Stoneley modes should offer better constraints, because they are confined near to the fluid-solid interface, but this property also makes them difficult to detect. In this study, we use recently-developed finite-element approach to show that Stoneley modes can be excited and detected, but only in certain special cases. We first investigate the physical explanation for these cases. Next, we describe how they could be detected in seismic data, and the sensitivity of these data to the material properties. We illustrate this sensitivity by calculating the modes of a three-dimensional Earth model containing a large low-shear-velocity province (LLSVP). Finally, we present some preliminary observations. We hope that this new understanding will lead to new constraints on the material properties and morphology of the core-mantle boundary region. In turn, this information, especially the constraints on density, should help to answer questions about the Earth, for example in mantle convection (are LLSVPs thermally or chemically buoyant? Primordial or slab graveyards? Passive or active?) and core convection (does the outermost core have a stable stratification?).</p>

scholarly journals Synthetic seismic anisotropy models within a slab impinging on the core–mantle boundary

2014 ◽  
Vol 199 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Sanne Cottaar ◽  
Mingming Li ◽  
Allen K. McNamara ◽  
Barbara Romanowicz ◽  
Hans-Rudolf Wenk
Keyword(s):  
Seismic Anisotropy ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core

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>

Multiple inner core reflections from a Novaya Zemlya explosion

1972 ◽  
Vol 62 (4) ◽  
pp. 1063-1071 ◽  
Author(s):  
R. D. Adams
Keyword(s):  
Lower Bound ◽  
Inner Core ◽  
Nuclear Explosion ◽  
Outer Core ◽  
Low Velocity ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
Novaya Zemlya ◽  
The Core ◽  
Velocity Channel

Abstract The phases P2KP, P3KP, and P4KP are well recorded from the Novaya Zemlya nuclear explosion of October 14, 1970, with the branch AB at distances of up to 20° beyond the theoretical end point A. This extension is attributed to diffraction around the core-mantle boundary. A slowness dT/dΔ = 4.56±0.02 sec/deg is determined for the AB branch of P4KP, in excellent agreement with recent determinations of the slowness of diffracted P. This slowness implies a velocity of 13.29±0.06 km/sec at the base of the mantle, and confirms recent suggestions of a low-velocity channel above the core-mantle boundary. There is evidence that arrivals recorded before the AB branch of P2KP may lie on two branches, with different slownesses. The ratio of amplitudes of successive orders of multiple inner core reflections gives a lower bound of about 2200 for Q in the outer core.

The thermal signature of subducted lithospheric slabs at the core–mantle boundary

1998 ◽  
Vol 160 (3-4) ◽  
pp. 551-562 ◽  
Author(s):  
Catherine Mériaux ◽  
Amotz Agnon ◽  
John R. Lister
Keyword(s):  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Thermal Signature
Sign in / Sign up

Export Citation Format

Share Document