利用远震接收函数研究华北克拉通北部造山带地壳厚度及泊松比

Crustal thickness and Poisson’s ratio of orogenic belts in northern North China Craton using teleseismic receiver functions

  • 摘要: 对2006年10月—2009年9月华北克拉通北部太行山—燕山造山带及相邻区域115套宽频带流动台和6套甚宽频流动台的接收函数数据,使用预测反褶积方法进行处理,消除沉积层的影响;然后利用谐波校正的H-κ-c叠加方法,得到了华北克拉通北部造山带及邻近区域消除地壳S波方位各向异性及倾斜界面影响的地壳厚度及泊松比。研究结果表明,研究区地壳厚度呈现西厚东薄的整体特征,地壳厚度与地形存在高度相关性,且基本符合艾里(Airy)均衡理论。西部陆块泊松比较低,表明其相对稳定,中部造山带和东部陆块的泊松比分布不均匀,可能遭受过复杂的改造过程。结合前人的研究结果,推测怀来—延庆盆地及唐山南部存在地壳部分熔融和上地幔物质的上侵,石家庄北部存在下地壳拆沉,保定—房山一带下地壳拆沉后,受伸展作用影响遭遇地幔物质底侵。不同区域地壳结构的差异性导致了谐波矫正前后研究区地壳厚度及平均泊松比变化的分布不同。

     

    Abstract: The thickness and Poisson’s ratio of crust of the North China Craton (NCC) are of great significance to the study of lithospheric evolution of the North China Craton. We collected receiver functions from 115 broadband seismic stations and six very broadband seismic stations on the Taihang-Yanshan orogenic belt and its adjacent areas in the northern North China Craton recorded from October 2006 to September 2009. First we used predictive deconvolution method to eliminate the influence of sedimentary on receiver function waveform. Then the effects of S wave azimuthal anisotropy and interfaces dipping were corrected by using H-κ-c stacking method. Finally, the thickness and Poisson’s ratio of research area were obtained. Our results are featured by lateral variation. The crust thickness in the research area is thick in the western block and thin in the eastern block, and is highly correlated to the topography, which is consistence with Airy isostasy. The low Poisson’s ratio of western block represent relative stability of the crust, the distribution of Poisson’s ratio in central orogenic belt and eastern block is inhomogeneous, suggests that the complex transformation process has been suffered in the crust. Combined with the previous research results, we speculate that there existed partial melting and mantle upwelling in the lower crust of Huailai-Yanqing basin and southern Tangshan, and lower crust detachment might have occurred on the north of Shijiazhuang, and the lower crust of Baoding-Fangshan may have been suffered mantle upwelling under the influence of extension after its detachment. The different crust structures of different areas result in the differences of crustal thickness and Poisson’s ratio distribution which are obtained by H-κ-c stacking as well as H-κ stacking.

     

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