scholarly journals Waveform inversion of SS precursors: An investigation of the northwestern Pacific subduction zones and intraplate volcanoes in China

2016 ◽  
Vol 40 ◽  
pp. 77-90 ◽  
Author(s):  
Ramin M.H. Dokht ◽  
Yu Jeffrey Gu ◽  
Mauricio D. Sacchi
Keyword(s):  
Subduction Zones ◽  
Waveform Inversion ◽  
Northwestern Pacific ◽  
Ss Precursors

Mapping mantle flows underneath the North American and Caribbean Plates

2021 ◽  
Author(s):  
Hejun Zhu
Keyword(s):  
North American ◽  
Subduction Zones ◽  
Current Model ◽  
Waveform Inversion ◽  
Body Waves ◽  
Plate Motion ◽  
Cascadia Subduction Zone ◽  
Fast Axis ◽  
The North ◽  
Short Period

<p>In this talk, I will present a new 3-D azimuthally anisotropic tomographic model, namely US32, for the North American and Caribbean Plates. This model is constrained by using seismic data from USArray and full waveform inversion. The inversion uses data from 180 regional earthquakes recorded by 4,516 seismographic stations, resulting in 586,185 frequency-dependent phase measurements. Three-component short-period body waves and long-period surface waves are combined to simultaneously constrain deep and shallow structures. The current azimuthally anisotropic model US32 is the result of 32 pre-conditioned conjugate-gradient iterations. In the current model, I observe a complex depth-dependent pattern for fast axis directions across the North American and Caribbean Plates.<span>  </span>At shallow depths, these fast axis directions delineate local geological provinces, such as the Snake River Plain, Cascadia subduction zone, Rio Grand Rift, etc. At greater depths, the fast axis directions follow the absolute plate motion trajectories at most places. At depths around 700 km, the fast axis directions are perpendicular to the strikes of the mapped Farallon slab, suggesting the presence of 2-D corner flows induced by this ancient subduction underneath the mantle transition zone. In addition, underneath the Cascadia and Cocos subduction zones at depths from 250 to 500 km, the fast axis directions suggest the presence of toroid-mode mantle flows, following the geometry of fast downwelling materials.</p>

Tracking slabs beneath northwestern Pacific subduction zones

2012 ◽  
Vol 331-332 ◽  
pp. 269-280 ◽  
Author(s):  
Yu Jeffrey Gu ◽  
Ahmet Okeler ◽  
Ryan Schultz
Keyword(s):  
Subduction Zones ◽  
Northwestern Pacific

Constraining the 410-km discontinuity and slab structure in the Kuril subduction zone with triplication waveforms

2021 ◽  
Vol 228 (2) ◽  
pp. 729-743
Author(s):  
Jiaqi Li ◽  
Min Chen ◽  
Jieyuan Ning ◽  
Tiezhao Bao ◽  
Ross Maguire ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Wave Speed ◽  
Waveform Inversion ◽  
Body Waves ◽  
P Wave ◽  
Model Parameters ◽  
Fast Wave ◽  
Mantle Dynamics ◽  
Speed Increase

SUMMARY The detailed structure near the 410-km discontinuity provides key constraints of the dynamic interactions between the upper mantle and the lower mantle through the mantle transition zone (MTZ) via mass and heat exchange. Meanwhile, the temperature of the subducting slab, which can be derived from its fast wave speed perturbation, is critical for understanding the mantle dynamics in subduction zones where the slab enters the MTZ. Multipathing, i.e. triplicated, body waves that bottom near the MTZ carry rich information of the 410-km discontinuity structure and can be used to constrain the discontinuity depth and radial variations of wave speeds across it. In this study, we systematically analysed the trade-off between model parameters in triplication studies using synthetic examples. Specifically, we illustrated the necessity of using array-normalized amplitude. Two 1-D depth profiles of the wave speed below the Tatar Strait of Russia in the Kuril subduction zone are obtained. We have observed triplications due to both the 410-km discontinuity and the slab upper surface. And, seismic structures for these two interfaces are simultaneously inverted. Our derived 410-km discontinuity depths for the northern and southern regions are at 420$\pm $15 and 425$\pm $15 km, respectively, with no observable uplift. The slab upper surface is inverted to be located about 50–70 km below the 410-km discontinuity. This location is between the depths of the 1 and 2 per cent P-wave speed perturbation contours of a regional 3-D full-waveform inversion (FWI) model, but we found twice the wave speed perturbation amplitude. A wave speed increase of 3.9–4.6 per cent within the slab, compared to 2.0–2.4 per cent from the 3-D FWI model, is necessary to fit the waveforms with the shortest period of 2 s, indicating that high-frequency waves are required to accurately resolve the detailed structures near the MTZ.

Petrologic and geochemical role of serpentinite in subduction zones and plate interface domains

2015 ◽  
Vol 37 ◽  
pp. 61-64
Author(s):  
Marco Scambelluri ◽  
Enrico Cannaò ◽  
Mattia Gilio ◽  
Marguerite Godard
Keyword(s):  
Subduction Zones ◽  
Plate Interface

Seasonal migrations of pregnant blue shark Prionace glauca in the northwestern Pacific

2020 ◽  
Author(s):  
Y Fujinami ◽  
K Shiozaki ◽  
Y Hiraoka ◽  
Y Semba ◽  
S Ohshimo ◽  
...  
Keyword(s):  
Northwestern Pacific ◽  
Blue Shark ◽  
Prionace Glauca ◽  
Seasonal Migrations
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