| 青藏高原东北缘地壳S波速度结构及其动力学含义--远震接收函数提供的证据 |
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| 引用本文： | 张洪双, 高锐, 田小波, 滕吉文, 李秋生, 叶卓, 刘震, 司少坤. 青藏高原东北缘地壳S波速度结构及其动力学含义--远震接收函数提供的证据[J]. 地球物理学报, 2015, 58(11): 3982-3992, doi: 10.6038/cjg20151108 |
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| 作者姓名： | 张洪双 高锐 田小波 滕吉文 李秋生 叶卓 刘震 司少坤 |
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| 作者单位： | 1. 中国地质科学院地质研究所, 北京 100037; 2. 国土资源部深部探测与地球动力学重点开放实验室, 北京 100037; 3. 中国科学院地质与地球物理研究所, 北京 100029 |
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| 基金项目： | 国家自然科学基金(41104034,41174081,41274066,41430213,41574094,41574092),国家专项项目"深部探测技术与实验研究"(Sinoprobe-02)和地质调查项目(12120115027101)联合资助. |
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| 摘 要： | 利用青海和甘肃地震台网2007-2009年记录的远震波形资料,提取多频段P波接收函数,反演得到了青藏高原东北缘及相邻地块下方0~100 km深度的地壳和上地幔S波速度结构.结果表明:(1)青藏高原东北缘的上、下地壳之间普遍存在一个S波速度低速层,其深度由南端的约35 km 向北变浅约为20 km,推测该低速层为一壳内滑脱层,表明东北缘地区的上地壳变形与下地壳解耦,从滑脱层的深度分布可以认为青藏高原东北缘的地壳缩短自南向北进行,现阶段以上地壳增厚为主;(2)昆仑-西秦岭造山带的下地壳厚度较北侧的祁连地块薄,一种推测是西秦岭造山带的下地壳抗变形能力更强,也可能这种差异在块体拼合前已经存在;(3)青藏高原东北缘及鄂尔多斯和阿拉善地块的下地壳S波速度随深度的增加而增加,这种正梯度增加的S波速度结构反映较高黏滞性的下地壳,推测青藏高原东北缘的地壳结构不利于下地壳流的发育.
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| 关 键 词： | 青藏高原东北缘 地壳S波速度 接收函数 壳内低速层 滑脱层 |
| 收稿时间： | 2014-03-13 |
| 修稿时间： | 2015-09-18 |
Crustal Swave velocity beneath the northeastern Tibetan plateau inferred from teleseismic Pwave receiver functions |
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| ZHANG Hong-Shuang, GAO Rui, TIAN Xiao-Bo, TENG Ji-Wen, LI Qiu-Sheng, YE Zhuo, LIU Zhen, SI Shao-Kun. Crustal Swave velocity beneath the northeastern Tibetan plateau inferred from teleseismic Pwave receiver functions[J]. Chinese Journal of Geophysics (in Chinese), 2015, 58(11): 3982-3992, doi: 10.6038/cjg20151108 |
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| Authors: | ZHANG Hong-Shuang GAO Rui TIAN Xiao-Bo TENG Ji-Wen LI Qiu-Sheng YE Zhuo LIU Zhen SI Shao-Kun |
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| Affiliation: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; 2. Key laboratory of Eearth Probe and Geodynamics, Ministry of Land and Resources of the People's Republic of China, Beijing 100037, China; 3. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | The northeastern (NE) Tibetan Plateau is an ideal place for investigating the far field effects of collision between the Indian and Eurasian plates. By what ways the Tibetan crust is thickened and extended is a long-term debated issue for absence of convincing evidence for proving the existence of the inner-crustal low velocity zone and its role. Using teleseimic P wave data from the China Seismograph Network in Qinghai and Gansu provinces recorded from 2007 to 2009, the crustal S-wave velocity structure beneath the NE Tibet plateau is resolved.#br#The receiver function waveform inversion technique (PROGRAM330) is used to analyze the crustal S-wave velocity structure below seismic stations. The receiver functions are estimated by a time-domain iterative deconvolution method of Ammon (1991) with four different Gaussian coefficients (α=1.0, 1.5, 2.0 and 2.5). Firstly, receiver functions, which are much similar in waveforms and within a narrow range of back-azimuth (less than 10°) and ray parameter (less than 0.002), are stacked to enhance the main signal characteristics. To maintain the intrinsical details of the receiver functions, they are stacked without normal moveout. Results of Tian et al. (2013) and Li et al. (2006) are used as the constraints in the inversion process to reduce the uncertainty.#br#The results show thata relatively low velocity layer (LVL) exists between the upper and lower crust in the region between the East Kunlun fault and the Haiyuan fault. The depth of the LVL shallows northeastward from ~35 km to ~20 km along the surface movement direction, while the Moho uplifts. The variation in thickness of the upper crust is more obvious than the lower crust. The thickness of the lower crust (15~20 km) beneath the Kunlun-west Qinling orogenic belt is thinner than that beneath the adjacent Qilian block (25~30 km). Beneath the NE Tibetan plateau, as well as the Alashan and Ordos blocks, the S-wave velocity in the lower crust increases with depth.The whole crustal S-wave velocity increases with depth beneath the eastern part of the west Qinling orogenic belt, the Ordos and Alashan blocks.#br# It can be concluded that the observed LVL in the NE Tibetan plateau can act as an intra-crustdecollement/detechment to decouple the deformation between the upper and lower crust. The geometry of the LVL and the Moho indicates that the NE Tibetan crust is growing northeastward, and is predominated by upper-crustal thickening at present.The lower crust of the Kunlun-west Qinling orognic belt may be more rigid than the adjacent Qilian block and thus has experienced less deformation and crustal thickening. The lower crust of the NE Tibetan plateau is normal and possess high viscosity, so that is not conducive to the flow of the lower crust. |
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| Keywords: | Northeastern Tibetan plateau Crustal Swave velocity Receiver functions Intra-crustal lower velocity layer Decollement |
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