Results 1 to 10 of about 102 (81)
Strong ULVZ and Slab Interaction at the Northeastern Edge of the Pacific LLSVP Favors Plume Generation [PDF]
Geochemistry, Geophysics, Geosystems, 2022 Strong waveform complexities, including multipathing of the S diffracted phase and rapid changes in differential ScS‐S times, are observed for multiple deep Fiji earthquakes recorded at the USArray.
Voon Hui Lai +2 more
exaly +4 more sources
P diff Postcursors from the Base of the Hawaiian ULVZ
The Seismic RecordUltra-low velocity zones (ULVZs) are anomalous regions on the core–mantle boundary. In the past decade, several ULVZs, and particularly the Hawaiian ULVZ, have been studied using postcursors to core-diffracted S waves (Sdiff), which constrain their shear-
Sanne Cottaar +2 more
exaly +3 more sources
Kilometer-scale structure on the core–mantle boundary near Hawaii [PDF]
Nature Communications, 2022 A new paper constrains a high-resolution ultra-low velocity zone (ULVZ) structure at the base of the Hawaiian mantle. The authors further propose this to be a chemically distinct ULVZ with increasing iron content towards the core mantle boundary.
Zhi Li +3 more
doaj +2 more sources
Slab control on the mega-sized North Pacific ultra-low velocity zone [PDF]
Nature Communications, 2022 Ultra-low velocity zones (ULVZs) are localized small-scale patches with extreme physical properties at the core-mantle boundary. Here, the authors discover a mega-sized ULVZ (1,500 × 900 km) at the northern edge of the Pacific Large Low Velocity Province.
Jiewen Li, Daoyuan Sun, Dan J. Bower
doaj +2 more sources
A high-resolution map of Hawaiian ULVZ morphology from ScS phases [PDF]
Earth and Planetary Science Letters, 2021 We use core reflected ScS waves sensitive to a broad region of the core-mantle boundary beneath Hawaii to create the first high-resolution map of the Hawaiian ultralow-velocity zone (ULVZ). Positive ScS-S differential times are used to identify regions of strong slow velocity anomalies in the lowermost mantle, and the presence of pre/post-cursors ...
Sima Mousavi, Sanne Cottaar, Zhi Li
exaly +3 more sources
Detection of a ULVZ at the base of the mantle beneath the northwest Pacific [PDF]
Geophysical Research Letters, 2009 We used the Yellowknife seismic array (YKA) to measure the slowness of 1,371 P and Pdiff waves from earthquakes occurring in the circum‐Pacific region. The corresponding anomalies in P‐velocity show a sharp reduction of up to 6% across a patch of the lowermost mantle beneath the Northwest Pacific with lateral dimensions of several hundred kilometers ...
Yan Xu, Keith D. Koper
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Intermittent and lateral varying ULVZ structure at the northeastern margin of the Pacific LLSVP [PDF]
Journal of Geophysical Research: Solid Earth, 2017 AbstractThin patches with ultralow velocities have been proposed to exist at the core‐mantle boundary (CMB). The detection and mapping of ultralow velocity zones (ULVZs) are difficult, in part, because of limited source‐receiver geometries of seismic phases used in ULVZ modeling. Here we develop a new approach that simultaneously utilizes ScS precursor
Shule Yu, Edward Garnero, Mingming Li
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Historical Interstation Pattern Referencing (HIPR): An Application to PcP Waves Recorded in the Antarctic for ULVZ Imaging [PDF]
Journal of Geophysical Research: Solid Earth, 2021 AbstractMuch of our knowledge on deep Earth structure is based on detailed analyses of seismic waveforms that often have small amplitude arrivals on seismograms; therefore, stacking is essential to obtain reliable signals above the noise level. We present a new iterative stacking scheme that incorporates Historical Interstation Pattern Referencing ...
Samantha Hansen +2 more
exaly +3 more sources
An unsually large ULVZ at the base of the mantle near Hawaii
Earth and Planetary Science Letters, 2012 Abstract Previous studies have documented the presence of ultra-low-velocity-zones (ULVZs) at the base of the mantle, through observations of body wave complexities. Geometrically their heights are in the range of ∼ 5 – 30 km , while little is known about their lateral extent beyond about 102 km, due to limitations in sampling.
Barbara Romanowicz, Sanne Cottaar
exaly +2 more sources
Geophysical Journal International, 2023 SUMMARY We present a new data set of nearly 100 earthquakes which show clear evidence of the Hawaiian ultra-low velocity zone (ULVZ) in the S core-diffracted phase (Sdiff), representing the most comprehensive Sdiff data set of a ULVZ to date. Using a Bayesian inversion approach, as outlined in Martin et al., and a subset of the data set,
Thomas Bodin +2 more
exaly +5 more sources