| 利用接收函数方法研究西秦岭构造带及其邻区地壳结构 |
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| 引用本文： | 姚志祥,王椿镛,曾融生,楼海,周民都.利用接收函数方法研究西秦岭构造带及其邻区地壳结构[J].地震学报,2014,36(1):1-19. |
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| 作者姓名： | 姚志祥 王椿镛 曾融生 楼海 周民都 |
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| 作者单位： | 1.中国北京 100081 中国地震局地球物理研究所 |
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| 基金项目： | 国家自然科学基金项目(90914005)、 中央级公益性科研院所基本科研业务费专项(DQJB09B05)和国家科技专项“深部探测技术试验与集成(SinoProbe-2)”共同资助. |
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| 摘 要： | 根据西秦岭构造带及其周边地区117个宽频带地震台站的高质量波形数据， 利用远震P波接收函数的H-k叠加方法， 求得地壳厚度和平均波速比. 通过分析地壳厚度、 波速比及其关系和接收函数CCP叠加剖面， 研究了该区域的地壳结构特征. 结果表明, 研究区域内地壳结构差异大， 呈过渡带特征. 地壳厚度总体上呈北北西向分布， 自西南向东北逐渐减小. 羌塘块体地壳厚度为72 km， 渭河盆地附近为39 km. 西秦岭构造带的地壳厚度为42—56 km， 南北向莫霍界面平坦. 研究区域P波与S波波速比平均为1.74， 其中西秦岭构造带平均为1.72. 较低的波速比主要分布在西秦岭构造带、 祁连山块体、 松潘—甘孜地块北部以及香山—天景山断裂区域， 这可能是由于含长英质酸性岩组分的上地壳叠置增厚而导致的. 该区域缺少超高波速比， 表明这一区域发生岩浆底侵或上地壳熔融的可能性很小. 综合分析表明， 西秦岭构造带及邻区的地壳结构主要是由于青藏高原隆升并在向东北向扩张中受到周边块体的阻挡而引起的地壳构造变形所致. 西秦岭构造带的莫霍界面变化和波速比分布与该构造带经历碰撞地壳增厚后的伸展走滑运动有关.
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| 关 键 词： | 西秦岭构造带 接收函数 地壳厚度 波速比 青藏高原 |
| 收稿时间： | 2012-09-10 |
Crustal structure in western Qinling tectonic belt and its adjacent regions deduced from receiver functions |
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| Institution: | 1.Institute of Geophysics, China Earthquake Administration, Beijing 100081, China2.Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China |
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| Abstract: | Seismic waveform data from 117 broadband seismic stations in the western Qinling tectonic belt and its adjacent regions were used to compute crustal thickness and velocity ratio (vP/vS) by the H-k stacking method of receiver functions. Crustal structures were studied by analyzing the crustal thicknesses, velocity ratios and their relationship, as well as the receiver function images calculated with the common conversion point stacking method. The results show strong lateral variations and transitional features of crustal structures in this area. The crust thins from southwest to northeast. The crustal thickness varies from 72 km in the Qiangtang block to 39 km near the Weihe basin. The crustal thickness in western Qinling tectonic belt is 42—56 km, and NS-trending Moho depth shows little change. The average velocity ratio vP/vS is 1.74 in the study area and 1.72 in western Qinling tectonic belt. Lower velocity ratios mainly distribute in western Qinling tectonic belt, Qilian block, northern Songpan--Garze block and Xiangshan--Tianjingshan fault zone. Lower velocity ratios in this area are probably due to the thickened upper crust of the felsic acid rock composition. The lack of ultrahigh velocity ratios indicates that there is little possibility of magma underplating beneath the lower crust and significant partial melting in the upper crust. Crustal structures in the western Qinling tectonic belt and its adjacent regions are mainly caused by the crustal tectonic deformation occurred during continuous uplifting and northeastward spreading of the Tibetan Plateau as blocked by surrounding terrane. The characteristics of Moho interfaces and velocity ratios in the western Qinling tectonic belt are correlated with underwent extension and strike-slip movement after the collision orogeny and crustal thickening. |
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