| 远震P波接收函数揭示的张家口(怀来)—中蒙边境(巴音温多尔)剖面地壳厚度与泊松比 |
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| 引用本文： | 龚辰,李秋生,叶卓,张洪双,李文辉,贺传松,李英康.远震P波接收函数揭示的张家口(怀来)—中蒙边境(巴音温多尔)剖面地壳厚度与泊松比[J].地球物理学报,2016,59(3):897-911. |
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| 作者姓名： | 龚辰 李秋生 叶卓 张洪双 李文辉 贺传松 李英康 |
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| 作者单位： | 1. 中国地质科学院地质研究所, 国土资源部"深部探测与地球动力学"重点实验室, 北京 100037;2. 中国地震局地球物理研究所, 北京 100081;3. 国土资源实物地质资料中心, 河北 燕郊 065201 |
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| 基金项目： | 国家自然科学基金(41174081)和"深部探测技术与实验研究"专项(Sinoprobe-02-03,公益科研专项项目编号201311156)联合资助. |
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| 摘 要： | 本文使用时间域迭代反褶积算法,从张家口(怀来)—巴音温多尔一线布设的41个宽频地震台站、1年期间记录的连续三分量数据中提取到高质量的P波接收函数1844个.用H-κ扫描方法获得了测线下方Moho深度与波速比值(VP/VS)进而计算出泊松比,用共转换点(CCP)叠加方法获得了沿测线Moho面起伏图像.结果显示:(1)测线下方Moho深度平均40km,仅各块体边界处出现Moho深度小尺度急剧变化.整体上,Moho面产状相对于索伦缝合带大致对称,在缝合带南侧的温都尔庙带和白乃庙带下方呈南倾趋势,在缝合带北侧的宝力道带、贺根山杂岩带下方呈北倾趋势.(2)华北克拉通北缘泊松比总体较高,兴蒙造山带整体较低;各次级块体内部泊松比分布相对稳定,块体分界带附近往往存在泊松比值的升降扰动.(3)整条测线地壳厚度和泊松比之间存在弱的负相关关系,表明存在构造作用的影响.(4)整条测线泊松比呈现以索伦缝合带南缘为对称轴的非线性分布.本文所获得的地壳上地幔结构以及泊松比分布特征,支持古亚洲(索伦)洋(南北)双向俯冲,最终沿林西断裂闭合的动力学模式.
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| 关 键 词： | 兴蒙造山带 古亚洲洋 接收函数 地壳上地幔结构 泊松比 |
| 收稿时间： | 2015-02-05 |
Crustal thickness and Poisson ratio beneath the Huailai-Bayinonder profile derived from teleseismic receiver functions |
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| GONG Chen,LI Qiu-Sheng,YE Zhuo,ZHANG Hong-Shuang,LI Wen-Hui,HE Chuan-Song,LI Ying-Kang.Crustal thickness and Poisson ratio beneath the Huailai-Bayinonder profile derived from teleseismic receiver functions[J].Chinese Journal of Geophysics,2016,59(3):897-911. |
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| Authors: | GONG Chen LI Qiu-Sheng YE Zhuo ZHANG Hong-Shuang LI Wen-Hui HE Chuan-Song LI Ying-Kang |
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| Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Key Laboratory of Earthprobe and Geodynamics, Ministry of Land and Resource, Beijing 100037, China;2. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;3. Core and Samples Center of Land and Resources, Hebei Yanjiao 065201, China |
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| Abstract: | The Central Asian Orogenic Belt(CAOB) between the Siberia paleo-continent and the North China paleo-continent has a close relationship with the evolution of the Paleo-Asian Ocean. The Xing'an-Mongolia Orogenic Belt(XMOB) as eastern part of the CAOB is located in North China. It is generally considered that the closure of the Paleo-Asian Ocean resulted in the formation of the XMOB, but there remain some disputes about the tectonic attribute of the northern margin of the North China Craton and where the Paleo-Asian Ocean finally closed and how it behaves due to complex evolution process, extensive coverage of Cenozoic sediments and the lack of high resolution deep exploration data. Structures and some major discontinuities beneath stations can be imaged by the receiver function method. In recent years, this method has become a mature and effective tool for studying the velocity structure of the crust and upper mantle. By the H-κ stacking method, the P-to-S converted waves at the Moho discontinuity and their multiple reflections are used to calculate crust thickness and VP/VS ratio, which provide a way to study the rock composition of the crust and stress condition under stations.Funded by National Natural Science Foundation of China, Institute of Geology, Chinese Academy of Geological Sciences deployed 41 portable broadband seismic stations from Huailai county in northern North China to Bayinondor town near the China-Mongolia border. The profile extends along the reflection and refraction profile funded by Sinoprobe project, crossing the Yinshan-Yanshan orogenic belt, the Inner Mongolia paleo-uplift, the Bainaimiao arc, the Ondor sum subduction accretion complex, the Solonker suture zone(the Solonder suture zone, located between the North China plate and Siberia plate, representing the closure of the Paleo-Asian Ocean), the Baolidao arc accretion complex, the Hegenshan ophiolite arc accretion complex and the Uliastai active continental margin from south to north. Recorders were set to the continuous recording mode and the sampling frequency was set to 50 Hz. The average distance between two neighbouring stations is 15 km and the length of the profile is about 650 km. Up to December 2014, we got 421 GB raw data in total. First, we select 746 teleseismic events of mb>5 from 30 to 95 degrees and obtain their P waveforms from-20 s to 100 s with respect to the first P arrival time. Then, 3-component waveform data with high signal-noise ratio are pre-processed(including mean removal and linear removal) and pre-filtering at 0.02~2 Hz and then rotated Z-N-E to the Z-R-T coordinate system. Finally we obtain 1844 P-wave receiver functions by the time domain iterative deconvolution method. After that we obtain the crustal thicknesses, VP/VS ratios and Poisson ratios beneath the profile by the H-κ stacking method and image extension of the Moho interface by the Common Coversion Point(CCP) stacking method. The results are as follows:(1) The Moho depth on average is 40 km along the profile. The crust thickness changes little across different tectonic blocks but shows evident variation at the boundaries between the blocks. The Moho dips southward beneath the Ondor sum belt and the Bainaimiao belt, while dips northward beneath the Baolidao belt and the Hegenshan belt. The Linxi fault seems to be as the boundary dividing the northern margin of North China Craton(NCC) and the southern CAOB.(2) The Poisson ratio shows a correlation with the tectonic unit along the profile. The averaged Poisson ratio in the northern margin of NCC is larger than the southern part of CAOB. The Poisson ratio changes little within the blocks except nearby the boundaries of different blocks.(3) There is a negative correlation between the crust thickness and the Poisson ratio that indicates the lateral heterogeneities of the crust structure resulted from the tectonic deformation.(4) Poisson ratio of the crust along the profile presents an approximately nonlinear symmetric shape relating to the south margin of Solonker suture zone. The characteristics of the crust and mantle structure and distribution of Poisson ratio along the profile support the geodynamic model that the Paleo-Asian Ocean subducted and closed at the southern margin of the Solon suture zone(along the Linxi fault). |
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| Keywords: | Xing'an Mongolia Orogenic Belt Paleo-Asian Ocean Receiver function Crust and upper mantle structure Poisson ratio |
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