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ISSN 2096-7780 CN 10-1665/P

鹤峰断裂带地壳结构横向变化及其构造意义基于远震接收函数的约束

Crustal structural variations around the Hefeng fault: implications from teleseismic receiver function study on the Hefeng seismic station

  • 摘要: 武陵山褶皱带位于华南大陆西部,远离板块边缘,发育了非常典型的冲断-褶皱构造系统,其深部结构与构造特征反映了陆内环境下的地壳缩短和变形过程。本研究利用武陵山褶皱带内的湖北鹤峰地震台记录的三分量远震波形数据,提取接收函数并着重分析了Ps转换震相随远震事件反方位角的变化特征,揭示了鹤峰断裂两侧地壳结的构差异性。结果表明:来自SE方向事件的Ps震相与直达P波到时差约为4.5 s,来自W与NE方向事件的Ps震相与直达P波到时差约为5.5 s。Ps震相到时的显著差异反映了鹤峰断裂是一条可延伸到Moho界面深度的区域性断裂。CCP成像和H-κ扫描分析表明在鹤峰断裂两侧地壳厚度存在突变,由NW侧地壳比SE侧地壳厚~10 km,且鹤峰断裂北西侧地壳内部存在明显的速度间断面。本研究为深入理解武陵山地区陆内变形动力学机制与过程提供了新的地震学约束。

     

    Abstract: The Wuling fold belt, located on the western part of the South China continent, far away from plate margin, developed a very typical fold-and-thrust system, and its deep structural and tectonic features reflect the crustal shortening and deformation processes in the intra-continental environment. This study, using the three-component teleseismic waveform data recorded on the Hefeng seismic station in Hubei province within the Wuling fold belt, we extracted the receiver function and focused on analyzing the characteristics of the change in back azimuth of the Ps converted seismic phases with the teleseismic event, which revealed the differences in crustal structure between the two sides of the Hefeng fault. The key findings are as follows: the difference between the Ps and the direct P arrival time is about 4.5 s for the SE-directed event, while the difference between the Ps and the direct P arrival time is about 5.5 s for the W and NE directed events. The significant difference in the arrival times of the Ps phases reflects that the Hefeng fault is a regional fault that extends to the depth of the Moho. CCP imaging and H-κ scanning analysis show that there is a sharp contrast in the crustal thickness on both sides of the Hefeng fault, which is steeply increased from 30 km on the east side to about more than 40 km on the west side, and there is an obvious velocity discontinuity on the west side of the Hefeng fault. These findings may offer new constraints for a deeper understanding of the dynamic mechanisms and processes of intra-continental deformation in the Wuling Mountains.

     

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