Results 41 to 50 of about 204 (113)

Double-Array Stacking of Pcp Waveforms: an Application to the Investigation of Ultra-Low Velocity Zones (ULVZs) in the Southern Hemisphere

, 2023
Electronic Thesis or DissertationUltra-low velocity zones (ULVZs) are one of the most anomalous features in the Earth's interior. Located just above the core-mantle boundary (CMB), ULVZs are generally associated with decreased seismic velocities and ...
Agboola, Kayode Johnson
core   +1 more source

Valence/Spin States of Iron in Peridotite Glass to Megabar Pressure Implications for Dense Iron‐Rich Silicate Melt at the Bottom of the Mantle

Geophysical Research Letters, Volume 52, Issue 7, 16 April 2025.
Abstract We have conducted high‐pressure electrical conductivity and Mössbauer spectroscopic measurements of peridotite glass as an analog of silicate melts. We observed the shoulder feature in the Mössbauer spectra above 60 GPa due to the emergence of the new Fe2+ component, which could be associated with the change of the iron partitioning ...
Izumi Mashino, Takashi Yoshino, Takaya Mitsui, Kosuke Fujiwara, Sayako Inoué, Takeshi Sakai   +5 more
wiley   +1 more source

Quantification of Small-Scale Heterogeneity at the Core–Mantle Boundary Using Sample Entropy of SKS and SPdKS Synthetic Waveforms

, 2022
Qualitative and quantitative analysis of seismic waveforms sensitive to the core–mantle boundary (CMB) region reveal the presence of ultralow-velocity zones (ULVZs) that have a strong decrease in compressional (P) and shear (S) wave velocity, and ...
Tarje Nissen-Meyer, Surya Pachhai, Michael S. Thorne   +2 more
core   +1 more source

Subducted Slab Slipping Underneath the Northern Edge of the Pacific Large Low‐Shear‐Velocity Province in D″

Journal of Geophysical Research: Solid Earth, Volume 130, Issue 4, April 2025.
Abstract We conduct waveform inversion for the 3‐D seismic shear wave (S‐wave) velocity structure in the lowermost mantle near the northern edge of the Pacific large low‐shear‐velocity province (LLSVP). We image a slab‐like high‐velocity anomaly slipping beneath the Pacific LLSVP in the lowermost 200 km of the mantle, extending toward an ultra‐low ...
Keisuke Otsuru, Kenji Kawai, Robert J. Geller   +2 more
wiley   +1 more source

Seismological Structure of the Earth's Lowermost Outer Core (F Layer) Beneath the East‐Central Pacific

Journal of Geophysical Research: Solid Earth, Volume 130, Issue 3, March 2025.
Abstract During the inner core solidification, excess light elements are released into the outer core, which causes outer‐core convection. To understand this process, it is important to determine the velocity structure of the bottom outer core (F layer). In previous studies, we developed an effective method that combines two independent observations to
Toshiki Ohtaki, Satoshi Kaneshima, Taku Tsuchiya   +2 more
wiley   +1 more source

SPdKS analysis of ultralow-velocity zones beneath the western Pacific

, 2013
We collected a new data set of 1354 broadband SPdKS waveforms sampling the western Pacific Ocean region. These data indicate that multiple ultralow-velocity zones (ULVZs) exist in this region.
Rost, S, Jensen, KJ, Thorne, MS
core   +1 more source

Ultra-low velocity zones beneath the Philippine and Tasman Seas revealed by a trans-dimensional Bayesian waveform inversion [PDF]

, 2016
Ultra-low velocity zones (ULVZs) are small-scale structures in the Earth's lowermost mantle inferred from the analysis of seismological observations. These structures exhibit a strong decrease in compressional (P)-wave velocity, shear (S)-wave velocity ...
Dettmer, Jan, Tkalčić, Hrvoje, Pachhai, Surya   +2 more
core   +1 more source

No Temporal Change Seen in High‐Frequency Waves Scattered Near the Core‐Mantle Boundary

Geophysical Research Letters, Volume 51, Issue 23, 16 December 2024.
Abstract The core‐mantle boundary (CMB) and the outermost core are dynamic and heterogeneous regions with time‐dependent flows. We examine two seismic raypaths, diffracted P and PKP precursors—both replete with scattering, with precisely repeating earthquakes.
Ruoyan Wang, John E. Vidale, Wei Wang
wiley   +1 more source

Iron Content‐Dependence of Ferropericlase Elastic Properties Across the Spin Crossover From Novel Experiments and Machine Learning

Geophysical Research Letters, Volume 51, Issue 22, 28 November 2024.
Abstract The iron spin crossover in (Mg1‐xFex)O ferropericlase causes changes to its physical properties that are expected to affect seismic velocities in Earth's lower mantle. We present new time‐resolved pressure‐volume measurements of iron‐rich ferropericlase (xFe = 0.40, 0.59) and combine the results with literature data with xFe = 0.04–0.6 to ...
V. E. Trautner, A. Rijal, C. Plueckthun, N. Satta, E. Koemets, J. Buchen, B. Wang, K. Glazyrin, L. Cobden, H. Marquardt   +9 more
wiley   +1 more source

Structural Evolution of Basaltic Melts in the Deep Earth: Insights From High‐Pressure Sound Velocity of Glass

Journal of Geophysical Research: Solid Earth, Volume 129, Issue 9, September 2024.
Abstract The densification mechanisms of silicate melts under high pressure are of key interest in understanding the evolution of the early Earth and its present‐day internal structure. Here, we report Brillouin spectroscopy‐derived transverse acoustic wave velocities VS $\left({V}_{S}\right)$ from a basaltic glass at high pressures up to 163 GPa and ...
Charlotte Trubowitz, Motohiko Murakami, Sylvain Petitgirard, Christian Liebske, Catherine McCammon   +4 more
wiley   +1 more source