scholarly journals A ubiquitous low-velocity layer at the base of the mantle transition zone

2014 ◽  
Vol 41 (3) ◽  
pp. 836-842 ◽  
Author(s):  
Xuzhang Shen ◽  
Xiaohui Yuan ◽  
Xueqing Li
Keyword(s):  
Transition Zone ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
Low Velocity Layer ◽  
Velocity Layer

Detection of a Thick and Weak Low‐Velocity Layer atop the Mantle Transition Zone beneath the Northeastern South China Sea from Triplicated P‐Wave Waveform Modeling

2019 ◽  
Vol 109 (4) ◽  
pp. 1181-1193 ◽  
Author(s):  
Guohui Li ◽  
Yunyue Elita Li ◽  
Heng Zhang ◽  
Ling Bai ◽  
Lin Ding ◽  
...  
Keyword(s):  
South China Sea ◽  
Transition Zone ◽  
South China ◽  
P Wave ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
P Wave Velocity ◽  
Low Velocity Layer ◽  
Northeastern South China Sea ◽  
Velocity Layer

Abstract Triplicated P waveforms related to the 410‐km discontinuity from five intermediate‐depth earthquakes in the central Philippines are clearly recorded by the Chinese Digital Seismic Network, but some branches of the S‐wave triplications are obscure. Matching the observed P‐wave triplications with synthetics through a grid‐search technique, we obtain the best‐fit 1D P‐wave velocity model near the 410‐km discontinuity beneath the northeastern South China Sea. In such a model, a low‐velocity layer (LVL) is found to reside atop the mantle transition zone, and it is characterized by a thickness of 92.5±11.5  km and a P‐wave velocity decrement of 1.5%±0.1% compared with the IASP91 model. The relatively thick and weak LVL is possibly a response of a small amount of remnant hydrous partial melts after plume‐like upwelling.

scholarly journals Pervasive low-velocity layer atop the 410-km discontinuity beneath the northwest Pacific subduction zone: Implications for rheology and geodynamics

2021 ◽  
Vol 554 ◽  
pp. 116642
Author(s):  
Guangjie Han ◽  
Juan Li ◽  
Guangrui Guo ◽  
Walter D. Mooney ◽  
Shun-ichiro Karato ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Northwest Pacific ◽  
Low Velocity ◽  
Low Velocity Layer ◽  
Velocity Layer

Focal mechanisms of earthquakes related to the 29 November 1975 Kalapana, Hawaii, earthquake: The effect of structure models

1981 ◽  
Vol 71 (3) ◽  
pp. 713-729 ◽  
Author(s):  
R. S. Crosson ◽  
E. T. Endo
Keyword(s):  
Main Shock ◽  
Horizontal Layer ◽  
Focal Mechanisms ◽  
Local Network ◽  
The South ◽  
Low Velocity ◽  
Tectonic Model ◽  
Low Velocity Layer ◽  
Using Data ◽  
Velocity Layer

abstract Initial focal mechanism determinations for the 29 November 1975 Kalapana, Hawaii, earthquake indicated discrepancy between the mechanism determined from teleseismic data by Ando and the mechanism determined using data from the local U.S. Geological Survey network surrounding the epicenter region. The resolution of this difference is crucial to correctly understand this earthquake, as well as to understand the tectonics of the south flank of Kilauea volcano. When a model with a low-velocity layer at the base of the crust is used for projection back to the focal sphere for the local network mechanisms, the discrepancy vanishes. To further investigate this result, focal mechanisms were determined using several contrasting models for a set of well-recorded earthquakes. A large number of these earthquakes have mechanisms identical to the main shock when the low-velocity layer model is used. Dispersion of P and T axes is also minimized by use of this model. A low-angle slip direction, favored for the main shock and typical of most other solutions, exhibits remarkable stability normal to the east rift zone of Kilauea. Our results suggest a tectonic model, similar in nature to that proposed by Ando, in which the south flank of Kilauea consists of a mobile block of crust which is relatively free to move laterally on a low-strength zone at about 10 km depth. Forceful injection of magma along the rift zones provides the loading stress which is released by catastrophic failure in the weak, horizontal layer in a cycle of perhaps 100 yr.

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