scholarly journals Double beam analysis of anomalies in the core-mantle boundary region

1993 ◽  
Vol 20 (14) ◽  
pp. 1475-1478 ◽  
Author(s):  
Frank Krüger ◽  
Michael Weber ◽  
Frank Scherbaum ◽  
Jörg Schlittenhardt
Keyword(s):  
Boundary Region ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Beam Analysis ◽  
Double Beam

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.

The core-mantle boundary region

1995 ◽  
Vol 100 (B4) ◽  
pp. 6397-6420 ◽  
Author(s):  
David E. Loper ◽  
Thorne Lay
Keyword(s):  
Boundary Region ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core

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>

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