Crust–mantle coupling at the northern edge of the Tibetan plateau: Evidence from focal mechanisms and observations of seismic anisotropy

2013 ◽  
Vol 584 ◽  
pp. 221-229 ◽  
Author(s):  
Vadim Levin ◽  
Guo-chin Dino Huang ◽  
Steven Roecker
Keyword(s):  
Tibetan Plateau ◽  
Seismic Anisotropy ◽  
Focal Mechanisms ◽  
The Tibetan Plateau ◽  
Northern Edge

scholarly journals Characteristics and sources of dissolved organic matter in a glacier in the northern Tibetan Plateau: differences between different snow categories

2018 ◽  
Vol 59 (77) ◽  
pp. 31-40 ◽  
Author(s):  
Lin Feng ◽  
Yanqing An ◽  
Jianzhong Xu ◽  
Shichang Kang
Keyword(s):  
Organic Matter ◽  
Tibetan Plateau ◽  
Dissolved Organic Matter ◽  
Melting Rate ◽  
Ion Cyclotron Resonance ◽  
The Tibetan Plateau ◽  
Mountain Glaciers ◽  
Northern Tibetan Plateau ◽  
Fresh Snow ◽  
Northern Edge

AbstractDissolved organic matter (DOM) in mountain glaciers is an important source of carbon for downstream aquatic systems, and its impact is expected to increase due to the increased melting rate of glaciers. We present a comprehensive study of Laohugou glacier no. 12 (LHG) at the northern edge of the Tibetan Plateau to characterize the DOM composition and sources by analyzing surface fresh snow, granular ice samples, and snow pit samples which covered a whole year cycle of 2014/15. Excitation–emission matrix fluorescence spectroscopy analysis of the DOM with parallel factor analysis (EEM-PARAFAC) identified four components, including a microbially humic-like component (C1), two protein-like components (C2 and C3) and a terrestrial humic-like component (C4). The use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) showed that DOM from all these samples was dominated by CHO and CHON molecular formulas, mainly corresponding to lipids and aliphatic/proteins compounds, reflecting the presence of significant amounts of microbially derived and/or deposited biogenic DOM. The molecular compositions of DOM showed more CHON compounds in granular ice than in fresh snow, likely suggesting newly formed DOM from microbes during snowmelting.

Seismic Anisotropy of Upper Mantle in the Northeastern Margin of the Tibetan Plateau

2008 ◽  
Vol 51 (2) ◽  
pp. 298-306 ◽  
Author(s):  
Li-Jun CHANG ◽  
Chun-Yong WANG ◽  
Zhi-Feng DING ◽  
Min-Du ZHOU ◽  
Jian-Si YANG ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Upper Mantle ◽  
Seismic Anisotropy ◽  
The Tibetan Plateau

Multilayered Crustal Anisotropy in Eastern Tibet Revealed by Receiver Function Data

2020 ◽  
Author(s):  
Shaohua Qi ◽  
Qiyuan Liu ◽  
Jiuhui Chen ◽  
Biao Guo
Keyword(s):  
Tibetan Plateau ◽  
Lower Crust ◽  
Seismic Anisotropy ◽  
Receiver Function ◽  
Azimuthal Anisotropy ◽  
Strain History ◽  
The Tibetan Plateau ◽  
Anisotropy Axis ◽  
Upper Crust ◽  
Western Sichuan

<p>It is widely accepted that the ongoing India-Asia collision since approximately 50 Ma ago has resulted in the uplift and eastward expansion of the Tibetan Plateau. Yet the interpretations of its dynamic process and deformation mechanism still remain controversial. Distinct models that emphasize particular aspects of the tectonic features have been proposed, including fault-controlled rigid blocks, continuous deformation of lithosphere and lower crust flow.</p><p>One possible way to reconcile these models is to investigate crustal deformation at multiple depths simultaneously, as well as crust-mantle interaction. Seismic anisotropy is considered as an effective tool to study the geometry and distribution of subsurface deformation, due to its direct connection to the stress state and strain history of anisotropic structures and fabrics. In the eastern margin of Tibetan plateau, previous studies of seismic anisotropy have already provided useful insights into the bulk anisotropic properties of the entire crust or upper mantle, based on shear wave splitting analyses of Moho Ps and XKS phases.</p><p>In this study, we went further to extract anisotropic parameters of multiple crustal layers by waveform inversion of teleseismic receiver function (RF) data from the western-Sichuan temporal seismic array using particle swarm optimization. Instead of directly fitting the backazimuthal stacking of RFs from each station, we translated the RF data into backazimuthal harmonic coefficients using harmonic decomposition technique, which separates the signals (of planar isotropic structure and anisotropy) from the scattering noise generated by non-planar lateral heterogeneity. The constant (k=0) and k=1, 2 terms of backazimuthal harmonic coefficients were used in our inversion. We also fixed the anisotropic model to slow-axis symmetry to avoid ambiguous interpretations.</p><p>Our results show that:</p><p>(1) Anisotropy with a titled anisotropy axis of symmetry is more commonly observed than pure azimuthal anisotropy in our data, which has been also reported by other RF studies across the surrounding areas of Tibetan plateau.</p><p>(2) The trends of slow symmetry axis vary from the upper to lower part of the crust in both Chuandian and Songpan units, indicating the deformation of the upper crust is decoupled from that of the lower crust in these two regions, while the trends are more consistent throughout the crust in the Sichuan basin.</p><p>(3) In the upper crust, the trends show a degree of tendency to lie parallel to the major geological features such as the Xianshuihe and Longmenshan faults, exhibiting a fault-controlled deformation or movement. In the middle and lower crust, the trends are NS or NW-SE in Chuandian unit and NE-SW in Songpan unit, which are coincident with the apparent extension directions of the ductile crustal flow.</p>

scholarly journals Interaction of the Westerlies with the Tibetan Plateau in Determining the Mei-Yu Termination

2020 ◽  
Vol 33 (1) ◽  
pp. 339-363 ◽  
Author(s):  
Wenwen Kong ◽  
John C. H. Chiang
Keyword(s):  
Tibetan Plateau ◽  
Meridional Wind ◽  
Northeastern China ◽  
The Tibetan Plateau ◽  
Stationary Waves ◽  
Diagnostic Analysis ◽  
Model Simulations ◽  
Northern Edge ◽  
Orographic Forcing ◽  
Jet Axis

AbstractThis study explores how the termination of the mei-yu is dynamically linked to the westerlies impinging on the Tibetan Plateau. It is found that the mei-yu stage terminates when the maximum upper-tropospheric westerlies shift beyond the northern edge of the plateau, around 40°N. This termination is accompanied by the disappearance of tropospheric northerlies over northeastern China. The link between the transit of the jet axis across the northern edge of the plateau, the disappearance of northerlies, and termination of the mei-yu holds on a range of time scales from interannual through seasonal and pentad. Diagnostic analysis indicates that the weakening of the meridional moisture contrast and meridional wind convergence, mainly resulting from the disappearance of northerlies, causes the demise of the mei-yu front. The authors propose that the westerlies migrating north of the plateau and consequent weakening of the extratropical northerlies triggers the mei-yu termination. Model simulations are employed to test the causality between the jet and the orographic downstream northerlies by repositioning the northern edge of the plateau. As the plateau edge extends northward, orographic forcing on the westerlies strengthens, leading to persistent strong downstream northerlies and a prolonged mei-yu. Idealized simulations with a dry dynamical core further demonstrate the dynamical link between the weakening of orographically forced downstream northerlies with the positioning of the jet from south to north of the plateau. Changes in the magnitude of orographically forced stationary waves are proposed to explain why the downstream northerlies disappear when the jet axis migrates beyond the northern edge of the plateau.

scholarly journals Antigorite‐induced seismic anisotropy and implications for deformation in subduction zones and the Tibetan Plateau

2014 ◽  
Vol 119 (3) ◽  
pp. 2068-2099 ◽  
Author(s):  
Tongbin Shao ◽  
Shaocheng Ji ◽  
Yosuke Kondo ◽  
Katsuyoshi Michibayashi ◽  
Qian Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
The Tibetan Plateau

Mesozoic and Cenozoic tectonics of the northern edge of the Tibetan plateau: fission-track constraints

2001 ◽  
Vol 343 (1-2) ◽  
pp. 111-134 ◽  
Author(s):  
M Jolivet ◽  
M Brunel ◽  
D Seward ◽  
Z Xu ◽  
J Yang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Fission Track ◽  
The Tibetan Plateau ◽  
Cenozoic Tectonics ◽  
Northern Edge
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