P-velocity structure of the core-mantle boundary region inferred from PKP(AB)-PKP(BC) differential travel times

1996 ◽  
Vol 23 (8) ◽  
pp. 853-856 ◽  
Author(s):  
Matthieu Sylvander ◽  
Annie Souriau
Keyword(s):  
Velocity Structure ◽  
Boundary Region ◽  
Travel Times ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core

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

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

Problems related to PcP and the core-mantle boundary illustrated by two nuclear events

1973 ◽  
Vol 63 (6-1) ◽  
pp. 2047-2070 ◽  
Author(s):  
Goetz G. R. Buchbinder ◽  
Georges Poupinet
Keyword(s):  
Inner Core ◽  
Wave Form ◽  
Model Parameters ◽  
Travel Times ◽  
P Waves ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Order Of Magnitude

Abstract Two large nuclear explosions produced a considerable number of PcP phases. Analysis of the P and PcP travel times shows a scatter of ±2 sec. It is pointed out that PcP and P times must be considered together to eliminate gross upper mantle effects on the travel times. On a worldwide basis, the PcP peak-to-peak amplitudes exhibit a scatter of up to one order of magnitude, and, thus, the reflection coefficient of the core-mantle boundary (cmb) may not be determined with any significance from them. Comparing the wave form of PcP and the wave form of P waves convolved with thin-layered models of the cmb suggests that the cmb may be approximated by a thin high-impedance liquid layer of several kilometers in thickness embedded between the mantle and the core. Such a model can explain observed dilatational arrivals and a small decrease in amplitude near Δ ≈ 30°. The data do not permit exact determination of the model parameters because of uncertainty in the data and insensitivity of the method and because the cmb also may be laterally inhomogeneous. The frequency-dependence of the reflection and transmission coefficients of a layered cmb would have serious effects on the determination of inner core parameters.

The velocities in the outer core

1971 ◽  
Vol 61 (4) ◽  
pp. 1051-1059
Author(s):  
A. L. Hales ◽  
J. L. Roberts
Keyword(s):  
Velocity Distribution ◽  
Lower Limit ◽  
Outer Core ◽  
Time Of Arrival ◽  
Travel Times ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Arc Distance ◽  
The Difference

abstract Earlier studies of the velocity distribution in the outer core have been based on the travel times of SKS.SKS arrivals can only be observed satisfactorily for arc distances at the surface greater than 85°. This lower limit of observation of SKS corresponds to an arc distance of 40.2° within the core. Thus the velocities in the outermost 250 km of the core are based upon an extrapolation. We have used observations of the difference in time of arrival of SKKS and SKS to obtain core travel times extending the range of observation down to a Δ within the core of about 14°. The velocity distribution thus found is significantly lower than those of Jeffreys (Bullen, 1963) and Randall (in press) near the core mantle boundary.

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