Tomographic investigation of the upper crustal structure and seismotectonic environments in Yunnan Province
Tomographic investigation of the upper crustal structure and seismotectonic environments in Yunnan Province
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DOI：
10.1007/s11589-003-0015-8
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发表时间：
2003-03
影响因子：
--
通讯作者：
Z. Bai;Chun-yong Wang
中科院分区：
文献类型：
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作者：
Z. Bai;Chun-yong Wang
利用云南省四条地震剖面丰富的地震测深资料，对云南省上地壳结构和地震构造环境进行了研究。导出的速度模型与出露盆地、隆起和断层有良好的对应关系。同时也揭示了与火山相对应的低速异常。云南地区上地壳存在明显的横向不均匀性。结晶基底的深度一般为0 ~ 5 km，有些地方碎屑岩直接出露于地面，但沉积盖层的厚度也可达8 km，有些大型凹陷甚至可达12 km。昌宁-双江断裂虽然是两个一级构造单元的分界线，但其在地壳内的切割深度可能较浅。另一方面，被称为板块接缝的红河断裂有明显的延伸到中下地壳的证据。地质时代火山的广泛活动与现今地震的发生有着密切的关系。尽管地表某些地方的火山活动已停止，但中下地壳物质仍处于活动状态，仍存在着强烈的向上应力。由于地表火山活动的停止，来自下地壳和上地幔的能量大部分不能释放，因此在适当的构造位置聚集。此外，盆地水的饱和、其它流体的作用以及外部应力的影响也是云南地区强震发生的另一个直接原因。
Investigation has been made for the upper crust structure and seismotectonic environments in Yunnan Province using the plentiful DSS data of the four profiles. The derived velocity model has a good relationship with the exposed basins, uplifts and faults. The low velocity anomaly corresponding to the volcano also has been revealed. There exits a prominent lateral inhomogeneity within the upper crust of Yunnan region. The depth of crystalline basement generally ranges from 0 km to 5 km, and the bedrocks are exposed on the ground directly in some places, nevertheless the thickness of sedimentary cover also can reach to 8 km or even 12 km at some large depressions. Although the Changning-Shuangjiang fault is a boundary between two first class tectonic units, its incision depth within the crust maybe shallow. On the other hand, known as the plates’ seam, the Honghe fault has a distinct evidence of extending into the mid-lower crust. The widely spread activity of the volcanoes in the geological era has a close relationship with the earthquake’s occurrence nowadays. Despite of the ceasing of the volcanoes in some places on the ground, the material in the mid-lower crust is still active, and there still exists strong upward stress. As the ceasing of the volcanoes on the surface, most parts of the power from the lower crust and the upper mantle cannot be released; therefore it accumulates at some appropriate tectonic locations. Moreover, the saturation of the water from the basin, the action of other fluids, and the effects of the outer stress maybe another direct reason account for the strong earthquakes’ occurrence in Yunnan region.