李伟, 丁志峰, 孙伟家. 2019: 利用地震光照成像法研究青藏高原东南缘岩石圈间断面结构及其动力学意义. 地震学报, 41(5): 549-568. DOI: 10.11939/jass.20190037
引用本文: 李伟, 丁志峰, 孙伟家. 2019: 利用地震光照成像法研究青藏高原东南缘岩石圈间断面结构及其动力学意义. 地震学报, 41(5): 549-568. DOI: 10.11939/jass.20190037
Li Wei, Ding Zhifeng, Sun Weijia. 2019: Structure of lithospheric discontinuities beneath the southeast margin of Tibetan Plateau revealed by seismic daylight imaging and its dynamic significance. Acta Seismologica Sinica, 41(5): 549-568. DOI: 10.11939/jass.20190037
Citation: Li Wei, Ding Zhifeng, Sun Weijia. 2019: Structure of lithospheric discontinuities beneath the southeast margin of Tibetan Plateau revealed by seismic daylight imaging and its dynamic significance. Acta Seismologica Sinica, 41(5): 549-568. DOI: 10.11939/jass.20190037

利用地震光照成像法研究青藏高原东南缘岩石圈间断面结构及其动力学意义

Structure of lithospheric discontinuities beneath the southeast margin of Tibetan Plateau revealed by seismic daylight imaging and its dynamic significance

  • 摘要: 为了进一步认识青藏高原东南缘的构造演化等动力学问题以及该区域的深部孕震机理,本文使用位于该区域内的中国地震科学台阵探测项目的台站所记录到的远震P波波形数据,采用地震光照成像法获取了岩石圈间断面的结构,并讨论了该方法的准确性和稳定性。研究结果显示,青藏高原东南缘的岩石圈西薄东厚,其中:滇缅泰地块腾冲火山附近最薄,约为60 km,其较薄的岩石圈可能是软流圈地幔物质上涌造成的;扬子地块岩石圈厚度从四川盆地向南逐渐减薄,特别是四川盆地下方最厚,可达190 km左右;滇缅泰地块腾冲火山下方150 km深度左右探测到明显的间断面,该间断面可能是腾冲火山原始岩浆源的位置即岩浆源。本研究所得结果 “印支地块与滇缅泰地块结构的连续性” 进一步为印度板块的推挤作用造成腾冲火山低速物质向东溢出的结论提供了地震学证据。此外,研究区域最北端的剖面显示,峨眉山大火成岩省的内带在50—250 km深度范围及其上方地壳内存在明显的局部高速异常,其不均匀分布特征可能与二叠纪火山喷发过程中岩浆底侵及中新生代以来多期次构造活动有关。

     

    Abstract: In order to further understand the dynamic problems such as tectonic evolution and deep seismogenic mechanism of the southeastern margin of the Tibetan Plateau, the structure of the lithospheric discontinuity was obtained by seismic daylight imaging based on teleseismic P-wave waveform data recorded by stations of China Seismological Science Array Exploration Project located in the region, and the accuracy and stability of the method were also discussed. The results show that the lithospheric thickness in the southeastern margin of the Tibetan Plateau is thinner in the west and thicker in the east. The thinnest lithospheric thickness near Tengchong volcano in Yunnan-Myanmar-Thailand block is about 60 km. The thinner lithosphere may be caused by the upwelling of asthenosphere mantle material. The lithospheric thickness of the Yangtze block is gradually thinning from Sichuan basin to the south, especially the thickest beneath the Sichuan basin, whose lithospheric thickness can reach about 190 km. Meanwhile, obvious discontinuities have been detected at a depth of about 150 km beneath Tengchong volcano, which may be the original magma source of volcano. The continuity of the structure of the Indo-China block and the Yunnan-Myanmar-Thailand block further provides seismological evidence for the eastward spillover of low-velocity materials from Tengchong volcano caused by the pushing of the Indian Plate. The northernmost section of the studied area shows that there are obvious local high-velocity variations in the depth range of 50−250 km within the Emeishan Large Igneous Province and the crust above it. The uneven distribution characteristics may be related to the magma bottom intrusion during the Permian volcanic eruption and the multiple tectonic activities since the Mesozoic and Cenozoic.

     

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