华北地区深部地幔剪切波速度结构研究

本文分析了华北地区近50个台站下方800 km深度内的剪切波速度结构.结果发现华北地区不同构造单元之间速度结构差异很大，稳定地块速度随深度稳定增加，构造带内速度结构复杂，而且即使在同一构造单元内，不同区段之间速度结构也明显不同，如太行山构造带，反映了不同构造单元或各区段经历了各自不同的地质演化历史.环渤海地区及相关区域多个台站的速度结构显示，华北东部地区地幔软流层埋深浅、厚度大、速度低，反映了地幔上涌的特点；而在软流层或更深层次的地幔中没有发现埋深或厚度比较统一的高速或低速体，因此可能没有岩石圈或下地壳介质曾经拆沉进入地幔，这为东部岩石圈减薄的动力学机制提供了一定的深部地球物理约束.

Study on mantle shear wave velocity structures in North China

In this paper, the shear wave velocity structures beneath nearly 50 stations in North China were analyzed down to a depth of 800 kin. The results show that there exist large differences among different tectonic units. The velocity increases steadily with depth in stable blocks, but the velocity structures become complicated beneath tectonic belts. Even in the same tectonic unit, the structure is apparently dissimilar at different segment, such as the Taihangshan tectonic belt, which reflects that different tectonic units and segments experienced their respective geological evolutional histories. The structures beneath the area around Bohai Bay and its neighboring indicate that the mantle asthenosphere in eastern China is shallow, thick and with low velocity values, which illustrates the character of up-welling mantle. But, no uniform high velocity or low velocity bodies in similar depth or with similar thickness were found in the asthenosphere or in much deeper mantle under the stations in eastern China, so probably, no any lithosphere or lower crust had been detached into the mantle, which provides a deep geophysical constraint on the dynamic mechanism of the lithospheric thinning in eastern North China.