| 山西断陷带上地幔顶部Pn波速度结构与各向异性成像 |
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| 引用本文： | 殷伟伟,雷建设,黄金刚,张娜,张广伟,张冰.山西断陷带上地幔顶部Pn波速度结构与各向异性成像[J].地球物理学报,1954,63(12):4382-4395. |
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| 作者姓名： | 殷伟伟 雷建设 黄金刚 张娜 张广伟 张冰 |
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| 作者单位： | 1. 山西省地震局, 太原 030021;2. 应急管理部国家自然灾害防治研究院(地壳动力学重点实验室), 北京 100085 |
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| 基金项目： | 中国科学院战略性先导科技专项（B类）（XDB18000000），国家自然基金项目（41674901，U1939206，41530212），山西省科技厅面上青年基金项目（201801D221044）、山西太原大陆裂谷动力学国家野外科学观测研究站项目（NORSTY20-13）和山西省地震局青年项目（SBK-2023，SBK-1922，SBK-1825）联合资助. |
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| 摘 要： | 本研究拾取了中国数字测震台网固定台站记录的2008—2019年期间发生在山西断陷带及邻区2级以上天然地震事件及陕西神木、府谷等3级以上非天然地震事件共25304条高质量Pn到时数据，反演了山西断陷带及邻区上地幔顶部高分辨率Pn波速度结构与各向异性.研究结果显示，山西断陷带及邻区Pn波速度结构差异较大，大同火山及以南区域、忻定盆地、太行山造山带、华北盆地南部和吕梁山局部地区表现为显著的低波速异常，而运城盆地、临汾盆地北部、太原盆地、大同盆地北部、华北盆地北部和鄂尔多斯块体呈现明显的高波速异常.大同火山下方上地幔顶部的低波速异常与Pn快波方向呈现以火山为中心的近发散状结构特征，结合已有的远震上地幔成像结果，暗示大同火山岩浆可能来源于地幔深部，岩浆的底侵或热侵蚀作用造成了该地区岩石圈的破坏以及整个华北克拉通的"活化"，这一推论符合克拉通的热-化学侵蚀破坏模型.山西断陷带上地幔顶部速度异常形态较好的对应了研究区的地质构造，Pn快波速方向与地质构造的展布方向和SKS波各向异性的特征基本一致，说明变形形式以简单剪切为主，表明其形成和演化过程与上地幔物质运移过程有密切关系.
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| 关 键 词： | 山西断陷带 上地幔顶部 Pn波成像 速度结构 各向异性 |
| 收稿时间： | 2020-06-11 |
Pn velocity and anisotropic uppermost-mantle tomography in and around the Shanxi rift zone |
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| YIN WeiWei,LEI JianShe,HUANG JinGang,ZHANG Na,ZHANG GuangWei,ZHANG Bing.Pn velocity and anisotropic uppermost-mantle tomography in and around the Shanxi rift zone[J].Chinese Journal of Geophysics,1954,63(12):4382-4395. |
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| Authors: | YIN WeiWei LEI JianShe HUANG JinGang ZHANG Na ZHANG GuangWei ZHANG Bing |
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| Institution: | 1. Earthquake Administration of Shanxi Province, Taiyuan 030021, China;2. Key Laboratory of Crustal Dynamics, National Institute of Natural Hazards, MEMC, Beijing 100085, China |
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| Abstract: | In this study we manually pick 25304 high-quality Pn arrival-time data from seismograms of natural earthquakes with magnitudes greater than 2.0 in and around the Shanxi rift zone and non-natural earthquakes that occurred in Shenmu and Fugu counties, Shaanxi Province with magnitudes greater than 3.0, recorded at the Chinese digital permanent seismic stations during 2008 to 2019. Through the inversion of these arrival times, we establish a high-resolution Pn velocity and anisotropy model of the uppermost mantle beneath the Shanxi rift zone and adjacent areas. Our results show the existence of strong lateral heterogeneities in the study region. Prominent low Pn velocities are observed under the Datong volcano and Xinding basin, Taihangshan orogen belt, southern parts of North China Basin and parts of Lüliangshan orogen belt, whereas obvious high velocities are imaged under the Taiyuan, northern Yuncheng, Linfen, Datong, and North China Basins and the Ordos block. The low Pn velocities and fast direction of the uppermost mantle beneath the Datong volcano generally present a scattered structure centered on the volcano, combined with the imaging results of teleseismic events, suggesting that the magma of the Datong volcano may be related to the mantle upwelling, magmatic underplating or thermal erosion could lead to the lithosphere destruction and the activation of the North China Craton. This inference is consistent with the thermal-chemical erosion model of North China Craton destruction. The Pn velocity model of the uppermost mantle beneath the Shanxi rift zone is closely related to surface geology, and the fast directions of Pn anisotropy are consistent with the trend of the geological structure and the fast directions of SKS anisotropy. These results suggest that the deformation of the Shanxi rift is dominated by simple shear, and its formation and evolution process are closely related to the movement of the upper mantle materials. |
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| Keywords: | Shanxi rift zone Uppermost mantle Pn tomography Velocity Anisotropy |
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