scholarly journals Receiver function imaging of the mantle transition zone beneath the S outh C hina B lock

2015 ◽  
Vol 16 (10) ◽  
pp. 3666-3678 ◽  
Author(s):  
Haibo Huang ◽  
Nicola Tosi ◽  
Sung‐Joon Chang ◽  
Shaohong Xia ◽  
Xuelin Qiu
Keyword(s):  
Transition Zone ◽  
Receiver Function ◽  
Mantle Transition Zone

Foundered lithospheric segments dropped into the mantle transition zone beneath southern California, USA

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 200-204
Author(s):  
Youqiang Yu ◽  
Stephen S. Gao ◽  
Kelly H. Liu ◽  
Dapeng Zhao
Keyword(s):  
Transition Zone ◽  
Sierra Nevada ◽  
Southern California ◽  
Receiver Function ◽  
Active Tectonics ◽  
Mantle Transition Zone ◽  
Diverse Range ◽  
Transverse Ranges ◽  
The Pacific ◽  
Lateral Variations

Abstract The diverse range of active tectonics occurring in southern California, USA, offers an opportunity to explore processes of continental deformation and modification in response to the instability of the Pacific and Farallon plates. Here, we present a high-resolution receiver-function image of the mantle transition zone (MTZ). Our result reveals significant lateral heterogeneities in the deep mantle beneath southern California. Both seismic tomography and MTZ discontinuity deflections reveal foundered lithospheric segments that have dropped into the MTZ beneath the western Transverse Ranges, the Peninsular Ranges, and part of the southern Sierra Nevada. Water dehydrated from these foundered materials may contribute to the observed MTZ thickening. Our observations, combined with previous tomography and geochemical results, indicate that lithospheric foundering of fossil arc roots provides a way for geochemical heterogeneities to be recycled into the underlying mantle, and suggest that the foundered materials can play a significant role in inducing lateral variations of MTZ structure.

scholarly journals Common reflection point mapping of the mantle transition zone using recorded and 3-D synthetic ScS reverberations

2019 ◽  
Vol 220 (1) ◽  
pp. 724-736
Author(s):  
Samuel M Haugland ◽  
Jeroen Ritsema ◽  
Daoyuan Sun ◽  
Jeannot Trampert ◽  
Maria Koroni
Keyword(s):  
Transition Zone ◽  
Large Scale ◽  
Receiver Function ◽  
Wave Theory ◽  
Shear Velocity ◽  
Velocity Model ◽  
Reflection Point ◽  
Mantle Transition Zone ◽  
Point Mapping ◽  
Continental Scale

SUMMARY The method of ScS reverberation migration is based on a ‘common reflection point’ analysis of multiple ScS reflections in the mantle transition zone (MTZ). We examine whether ray-theoretical traveltimes, slownesses and reflection points are sufficiently accurate for estimating the thickness H of the MTZ, defined by the distance between the 410- and 660-km phase transitions. First, we analyse ScS reverberations generated by 35 earthquakes and recorded at hundreds of seismic stations from the combined Arrays in China, Hi-NET in Japan and the Global Seismic Network. This analysis suggests that H varies by about 30 km and therefore that dynamic processes have modified the large-scale structure of the MTZ in eastern Asia and the western Pacific region. Second, we apply the same procedure to spectral-element synthetics for PREM and two 3-D models. One 3-D model incorporates degree-20 topography on the 410 and 660 discontinuities, otherwise preserving the PREM velocity model. The other model incorporates the degree-20 velocity heterogeneity of S20RTS and leaves the 410 and 660 flat. To optimize reflection point coverage, our synthetics were computed assuming a homogeneous grid of stations using 16 events, four of which are fictional. The resolved image using PREM synthetics resembles the PREM structure and indicates that the migration approach is correct. However, ScS reverberations are not as strongly sensitive to H as predicted ray-theoretically because the migration of synthetics for a model with degree-20 topography on the 410 and 660: H varies by less than 5 km in the resolved image but 10 km in the original model. In addition, the relatively strong influence of whole-mantle shear-velocity heterogeneity is evident from the migration of synthetics for the S20RTS velocity model and the broad sensitivity kernels of ScS reverberations at a period of 15 s. A ray-theoretical approach to modelling long-period ScS traveltimes appears inaccurate, at least for continental-scale regions with relatively sparse earthquake coverage. Additional modelling and comparisons with SS precursor and receiver function results should rely on 3-D waveform simulations for a variety of structures and ultimately the implementation of full wave theory.

scholarly journals Receiver function imaging of mantle transition zone discontinuities and the origin of volcanism beneath Libya

2019 ◽  
Vol 124 ◽  
pp. 93-103 ◽  
Author(s):  
Awad A. Lemnifi ◽  
John Browning ◽  
Abdelsalam Elshaafi ◽  
Nassib S. Aouad ◽  
Y. Yu
Keyword(s):  
Transition Zone ◽  
Receiver Function ◽  
Mantle Transition Zone
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