Neotectonic activity along the Shanxi rift system, China
Neotectonic activity along the Shanxi rift system, China
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DOI：
10.1016/0040-1951(93)90180-r
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发表时间：
1993-03
期刊：
影响因子：
2.9
通讯作者：
Xi-wei Xu;Xing‐Da Ma;Q. Deng
中科院分区：
文献类型：
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作者：
Xi-wei Xu;Xing‐Da Ma;Q. Deng
山西裂谷系是我国最突出的上新世-第四纪大陆裂谷系和强震带之一。它是一系列雁列式左阶不对称半地堑盆地，在山西高原上延伸1200多公里。它描述了一个正弦的S形曲线，中间是NNE向的张扭段，两端是NE-ENE向的伸展域。后者以明显的同步高角度正断层活动为特征，可容纳较大的垂直应变和相对较小的侧向应变（3.5-8.5%），形成现代盆山结构。地貌、新构造和地震研究表明，裂谷系目前仍在发展，表现为7-8级历史强震的发生和中段北北东向扭张断裂的大滑动速率。地球物理研究表明，裂谷作用发生在增厚的地壳中，没有令人信服的证据表明地幔中的主要热事件与裂谷作用唯一相关。山西裂谷系的发育与区域右旋剪切带的脆性应变格局和华北亚板块ENE-WSW向挤压、NNW-SSE向伸展的区域应力场相一致。这种构造背景证实了这样一种假设，即变形是对来自西南的喜马拉雅压痕所引起的逃逸构造的响应，同时也是由中间地壳块体的逆时针旋转引起的。这为山西裂谷系的形成提供了模式。
The Shanxi rift system is one of the most outstanding Pliocene-Quaternary continental rift systems and strong earthquake belts in China. It extends as a series of en echelon left-stepping asymmetrical half-graben basins on the Shanxi Highlands over a distance of more than 1200 km. It describes a sinous S-shaped curve with a NNE-trending transtensional segment in the middle, and NE-ENE-trending extensional domains on both terminal segments. The latter are characterized by apparently synchronous, high-angle normal faulting, accommodating large vertical and relatively smaller lateral strains (3.5–8.5%), which produces the modern basin and range structure.The rift system has been intermittently active since the Pliocene. Geomorphological, neotectonic and seismic studies indicate that the rift system is at present still developing, as demonstrated by the occurrence of strong destructive historical earthquakes of magnitudes 7–8 and the large slip rates on the NNE-trending transtensional faults in the middle segment. The slip rates of these faults reached 4.9–6.4 mm per year during the Holocene.Geophysical studies show that the rifting occurred in a thickened crust, and no compelling evidence exists for the major thermal event in the mantle uniquely associated with the rifting. The development of the Shanxi rift system is consistent with the regional brittle strain pattern of a right-lateral shear belt and a regional stress field of ENE-WSW compression and NNW-SSE extension of the North China subplate. This structural setting corroborates the hypothesis that the deformation is in response to the escape tectonics caused by the Himalayan indenter from the southwest, and at the same time by the counter-clockwise rotation of the intervening crustal blocks. This provides the mode of formation of the Shanxi rift system.