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Seismic P-wave tomography in eastern Tibet: Formation of the rifts

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Chinese Science Bulletin 2011年第23期56卷 2450-2455页

作者： ZHANG Heng ZHAO JunMeng XU Qiang key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085China

为更好学习在裂缝和深结构之间的关系，在东方西藏下面的详细 P 波浪速度结构从由 51 个便携式的车站记录的 169 个 teleseismic 事件用 4767 到达时间被建模。在通过模型的水平片，一个突出的低速度的异例从表面在裂缝下面被检测到 250... 详细信息

为更好学习在裂缝和深结构之间的关系，在东方西藏下面的详细 P 波浪速度结构从由 51 个便携式的车站记录的 169 个 teleseismic 事件用 4767 到达时间被建模。在通过模型的水平片，一个突出的低速度的异例从表面在裂缝下面被检测到 250 km 的深度；这在垂直的片延长到 400 km 的深度。这个低速度的异例作为上面的披风 upwelling 被解释。做的观察为纵贯的 trending 裂缝的形成提供地震证据。低速度的异例的东方，一个清楚的高速度的异例在 40 和 200 km 的深度之间被发现。由于它的浅深度，我们建议它从古老的大陆人闭合而非印度板由材料组成。从 250 ～ 400 km 的深度，一个高速度的异例出现到 Jiali 差错的南方。这个异例可以对应于在喜玛拉雅的块下面从表面分开了的印度板的北边。我们建议印度板 underthrusts 不在东方西藏比 Jiali 差错推进。

关键词： P波速度结构西藏东部层析成像裂谷地震速度异常印度板块水平切片

Pn wave velocity and anisotropy beneath Pamir and its adjacent regions

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Earthquake Science 2012年第5期25卷 485-493页

作者： Biao Feng Shunping Pei key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau ResearchChinese Academy of Sciences University of Chinese Academy of Sciences

As the western end point of continental collision between the Indian and Eurasian plates, Pamir is an ideal place to research uplifting mechanisms in the Tibetan plateau. In this study, 141 644 Pn arrivals were used to obtain seismic wave velocities and anisotropy in the uppermost mantle beneath Pamir and its adjacent regions by performing tomographic inversion of Pn travel times. The data were selected from multiple databases, including ISC/EHB, the Annual Bulletin of Chinese Earthquakes, and regional bulletins of Xinjiang. The tomography results reveal significant features with high resolution and correlate well with geological structures. The main results are as follows：（1） The Pn wave velocities are particularly high in the old stable blocks such as Tarim basin, Indian plate and Tajik basin, while the low Pn velocities always lie in tectonically active regions like the western Tibetan plateau, Pamir, Tianshan and Hindu Kush. （2） Strong Pn anisotropy is found beneath the Indian-Eurasian collision zone; its direction is parallel to the collision are and nearly perpendicular to both the direction of maximum compression stress and relative crustal movement. The result is probably caused by the pure shear deformation in the uppermost mantle of the collision zone. （3） A geodynamic continent-continent collision model is proposed to show anisotropy and collision mechanisms between the Indian plate and the Tarim and Tajik basins.

关键词： Pn wave velocity tomography anisotropy Pamir

Differential surface uplift: Cenozoic paleoelevation history of the Tibetan plateau

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Science China Earth Sciences 2016年第11期59卷 2105-2120页

作者： LIU XiaoHui XU Qiang DING Lin key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences Center for Excellence in Tibetan plateau Earth Science Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences

The surface uplift history of the Tibetan plateau has provided a key boundary criterion for various geological, climatic,and environmental events since the Cenozoic. The paleoelevation history of the plateau is organically associated with interactions amongst deep geodynamics, earth surface processes, and climate change. Understanding of plateau uplift history has been advanced by the development of a number of paleoaltimetries and their application to studies of the Tibetan plateau: the paleogeomorphic scenario for the Early Eocene Tibetan plateau is thought to include two high mountains, the ca. 4500 m Gangdese Mountains to the south, and the ca. 5000 m Qiangtang Center Watershed Mountains to the north. Between these ranges, a low-elevation basin(ca. 2500 m) is thought to have been present. The Himalayas in the southern Tibetan plateau was close to sea level at this time,while the Hoh Xil Basin in the north reached an elevation of no more than 1500 m. Thus, the so-called "Roof of the World" Tibetan plateau formed subsequent to the Miocene. Nevertheless,, the uplift histories of the different terranes that comprise this plateau currently remain unclear, which constrains the uplift history reconstruction of the entire Tibetan plateau. Additional paleoelevation data from different areas, obtained using multi-paleoaltimeters, is required to resolve the forms and processes of Tibetan plateau uplift and extension.

关键词： Paleoelevation Differential surface uplift Cenozoic Tibetan plateau

Rupture process of the 2015 Pishan earthquake from joint inversion of InSAR, teleseismic data and GPS

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Science China Earth Sciences 2018年第10期61卷 1467-1481页

作者： Xun WANG Weimin WANG Junmeng ZHAO Zhenxing YAO key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences Institute of Geology and Geophysics Chinese Academy of Sciences

An earthquake of Mw6.4 occurred in Pishan County in Xinjiang Province, northwestern Tibetan plateau, on July 3,2015. The epicenter was located on an active blind thrust system located at the northern margin of the Western Kunlun Mountain Orogenic Belt southwest of the Tarim Basin. We constructed a shovel-shaped fault model based on the layered-crust model with reference to the seismic reflection profile, and obtained the rupture process of the earthquake from the joint inversion of Interferometric Synthetic Aperture Radar(InSAR) measurements, far-field waveform data, and Global Positioning System(GPS) data. The results show that the seismic fault dips southward with a strike of 109°, and the rupture direction was essentially northward. The fault plane rupture distribution is concentrated, with a maximum recorded slip of 73 cm. The main features of the fault are as follows: low inclination angle(25°–10°), thrust slip at a depth of 9–13 km, rupture propagation time of about 12 s, no significant slip in soft or hard sedimentary layers at 0–4 km depth and propagation from the initial rupture point to the surrounding area with no obvious directionality. The InSAR time-series analysis method is used to determine the deformation rate in the source region within 2 years after the earthquake, and the maximum value is ~17 mm yr-1 in the radar line-of-sight direction. Obvious post-earthquake deformation is evident in the hanging wall, with a similar trend to the coseismic displacement field. These results suggest that the Pishan earthquake has not completely released the accumulated energy of the region, given that the multilayer fold structure above the blind fault is still in a process of slow uplift since the earthquake. Post-earthquake adjustment models and aftershock risk analysis require further study using more independent data.

关键词： Pishan earthquake Source process Joint inversion Post-earthquake deformation

Geochemical Characteristics of Volcanic Rocks from ODP Site 794,Yamato Basin:Implications for Deep Mantle Processes of the Japan Sea

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Acta Geologica Sinica(English Edition) 2015年第4期89卷 1189-1212页

作者： CHEN Shuangshuang LIU Jiaqi GUO Zhengfu CHEN Shengsheng SUN Chunqing key laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences University of Chinese Academy of Sciences key laboratory of continental collision and plateau uplift Institute of Tibet Plateau ResearchChinese Academy of Sciences

Deep mantle processes and the dynamic mechanism of magmatism in the Japan Sea Basin are important processes that have not been studied in detail. In this paper, systematic evaluation of basalt samples from the ocean drilling program Site 794 in the Japan Sea was performed, which included petrography, whole-rock major- and trace-element analysis, Sr-Nd-Pb isotopic composition, and electron microprobe analysis of plagioclase and clinopyroxene. These basalts belong to the tholeiitic series with porphyritic texture and massive Ca-rich plagioclase, clinopyroxene, and minor olivine phenocrysts. The basalts are characterized as flat rare earth elements and high-field-strength elements with remarkably low ratios of （La/Yb）N （0.75-2.51）, significant positive anomalies of Ba, Sr, and Rb and no Eu anomaly （dEn = 0.99-1.36）. The samples showed relatively high 87Sr/86Sr （0.70425- 0.70522）, 207pb/204pb （15.511-15.610）, and 208pb/204pb （38.064-38.557） values and a low 143Nd/144Nd ratio （0.51271-0.51295）. The basalts from Site 794 can be divided into upper, middle, and lower volcanic rocks （UVR, MVR, and LVR） on the basis of their stratigraphic level. The MVR was geochemically derived from the depleted mantle, whereas the UVR and LVR originated from a nondepleted and relatively enriched mantle source with contributions from subducted Pacific plate fluid and sediments. Use of geothermobarometers indicates that the crystallization pressure for the UVR and LVR （6.25-11.19 kbar） was significantly higher than that of the MVR （3.48-5.84 kbar）. The UVR and LVR may have been derived from the low-degree （5%-10%） partial melting of spinel lherzolite, while the MVR originated from a shallower mantle source with a high degree （10%-20%） of partial melting. In addition, the geochemical characteristics of the samples are consistent with a younger age （13-17 Ma） and the depleted composition of the MVR and an older age （17-23 Ma） and slightly enriched composition of the UVR and LVR. Therefore, temp

关键词： Basalt deep mantle process geothermobarometer Yamato Basin

Focal depth estimates of earthquakes in the Himalayan-Tibetan region from teleseismic waveform modeling

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Earthquake Science 2012年第5期25卷 459-468页

作者： Ling Bai Jeroen Ritsema Junmeng Zhao key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau ResearchChinese Academy of Sciences Department of Earth and Environmental Sciences University of Michigan

We estimate the focal depths and fault plane solutions of 46 moderate earthquakes in the Himalayan- Tibetan region by modeling the broadband waveforms of teleseismic P waves. The depths of 38 of these earth- quakes range between 0-40 km, with a peak at -5 km. One earthquake is located within the lower crust of the Indian shield. The remaining eight earthquakes occurred between depths of 80 -120 km and are all located in the Pamir-Hindu Kush and the Indo-Myanmar deep seismic zones. None of the earthquakes outside these deep seismic zones are located in the mantle. Global centroid moment tensor （CMT） solutions indicate that most earthquakes in northern Tibet and northern India had thrust-faulting mechanisms and that normal and strike-slip faulting earthquakes occurred primarily in central Tibet. These mechanisms are consistent with the predominantly NNW-SSE compression in the direction of current Himalayan-Tibetan continental collision.

关键词： continental collision zone Tibetan plateau focal depth strength of the continental lithosphere

Paleoaltimetry reconstructions of the Tibetan plateau:progress and contradictions

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National Science Review 2015年第4期2卷 417-437页

作者： Tao Deng Lin Ding key laboratory of Vertebrate Evolution and Human Origins Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of Sciences CAS Center for Excellence in Tibetan plateau Earth Sciences key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau ResearchChinese Academy of Sciences

Over the last two decades, many quantitative paleoaltimetry reconstructions of the Tibetan plateau have been published, but they are still preliminary and controversial, although several approaches have been combined paleontology and geochemistry, including vertebrate, plant, and pollen fossils as well as oxygen,carbon, and hydrogen isotopes. he Tibetan plateau is the youngest and highest plateau on Earth, and its paleoaltimetry reconstructions are crucial to interpret its geodynamic evolution and to understand the climatic changes in Asia. Uplit histories of the Tibetan plateau based on diferent proxies difer considerably, and two viewpoints are pointedly opposing on the paleoaltimetry estimations of the Tibetan plateau. One viewpoint is that the Tibetan plateau did not strongly uplit to reach its modern elevation until the Late Miocene, but another one, mainly based on stable isotopes, argues that the Tibetan plateau formed early during the Indo-Asian collision and reached its modern elevation in the Paleogene or by the Middle Miocene. With either a geochemical or paleontological approach, the present is used as the key to the ***, there are great diiculties because modern processes of isotopic fractionation and species for creature distribution are not easily precisely determined. In addition, the climatic and environmental backgrounds of past geological times have massive diferences from the present, and associated adjustments are inluenced by many human factors. In the future work, the applications of multidisciplinary comprehensive methods and cross-checks of their results will be productive, and we look forward to achieving more reliable estimates for paleoelevations of the Tibetan plateau.

关键词： Tibetan plateau Cenozoic paleoelevation paleontology stable isotope

Dynamics of unstable continental subduction:Insights from numerical modeling

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Science China Earth Sciences 2017年第2期60卷 218-234页

作者： HUANGFU PengPeng WANG YueJun FAN WeiMing LI ZhongHai ZHOU YongZhi School of Earth Science and Geological Engineering Sun Yat-sen University key laboratory of Computational Geodynamics College of Earth SciencesUniversity of Chinese Academy of Sciences CAS Center for Excellence in Tibetan plateau Earth Sciences Key Laboratory of Continental Collision and Plateau UpliftInstitute of Tibetan Plateau ResearchChinese Academy of Sciences

Numerical experiments are used in this study to systematically investigate the effects of convergence rate,crustal rheological strength,and lithospheric thermal structure on the dynamics of continental *** study focuses on the types,conditions and processes of unstable continental *** results suggest that the development of unstable continental subduction can be promoted by conditions that tend to decrease rheological strength of the lithosphere,such as low crustal rheological strength,"hot"thermal structure of the lithosphere,or low convergence *** subduction mode can be further categorized into three types:(1)multi-stage slab breakoff,(2)continuously"flowing"of fluid-like slab into the upper mantle,and(3)large-scale detachment of the thickened orogenic *** three types of unstable continental subduction are respectively associated with(1)a low convergence rate,(2)"hot"thermal structure of the lithosphere with a high convergence rate,and(3)moderate-high crustal rheological strength with a low convergence *** is also revealed that the evolution of crustal melting is dominated by the deformation pattern of continental collision,which is mainly controlled by crustal rheological *** modelling results have important implications for understanding of continental subduction mode selection under specific geodynamic conditions.

关键词： Unstable continental subduction Stable continental subduction Slab breakoff Detachment Partial melting

Origin of middle Miocene leucogranites and rhyolites on the Tibetan plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary

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Chinese Science Bulletin 2012年第5期57卷 511-524页

作者： ZHANG LiYun DING Lin YANG Di XU Qiang CAI FuLong LIU DeLiang key laboratory of continental collision and plateau uplift Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100085China Graduate University of Chinese Academy of Sciences Beijing 100049China

Leucogranites 玩在理解外壳的变厚的一个重要角色，融化在大陆人 collisional 带，和高原以内高举。地调查证明来自霍·克西尔·莱克区域的中新世的火的岩石主要由二云母的 leucogranites 和流纹岩组成。我们学习了由锆石 U-Pb，白云母... 详细信息

Leucogranites 玩在理解外壳的变厚的一个重要角色，融化在大陆人 collisional 带，和高原以内高举。地调查证明来自霍·克西尔·莱克区域的中新世的火的岩石主要由二云母的 leucogranites 和流纹岩组成。我们学习了由锆石 U-Pb，白云母和 sanidine 40Ar/39Ar 地球年代学的 Bukadaban 二云母的 leucogranites 和凯考·莱克， Malanshan 和 Hudongliang 流纹岩，和整个岩石的 geochemical 和 Sr-Nd 同位素的分析。结果为 9.7 的 Bukadaban leucogranites 产出结晶化和冷却年龄 ????? ‰ ?????? 椠湯獯桰牥捩吗？？

关键词：淡色花岗岩时间约束地壳增厚青藏高原中中新世流纹岩自然科学基金会边界