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榆木山北缘断裂位于祁连山逆冲断裂带中部,是榆木山隆起与河西走廊之间的分界断裂。探究榆木山北缘断裂的构造活动,有助于进一步了解祁连山向N的扩展过程以及青藏高原向NE方向推挤的机制。文中主要从断层滑动速率、古地震活动习性和构造变形3个方面总结了榆木山地区近20多年以来的研究成果。通过遥感影像解译、野外地质调查、断错位移测量及地貌面年龄测定等方法和手段,估算了榆木山北缘断裂典型位错点的逆冲滑动速率为(0.55±0.15)mm/a;左旋滑动速率为(0.95±0.11)mm/a。认为前人提出的“骆驼城陡坎”并非断层活动的产物,而是古代引水工程或水利灌溉工程的遗迹,也就是说它不是公元180年表氏地震的地表破裂。通过DEM剖面所反映的山体形态,结合断裂各项特征,认为榆木山隆起是祁连山向N推挤的结果,断裂活动目前仍集中在榆木山北侧,山体的形态受断层扩展控制,山脉的扩展是1个垂向和侧向的过程,晚新生代以来榆木山持续隆升。
The northern margin of Elm Mountain is located in the middle part of Qilian thrust belt and is the boundary fault between Elm hill uplift and Hexi corridor. Studying the tectonic movement of faults along the northern margin of Elm Mountain helps to further understand the extension process of N to Q in Qilian Mountains and the thrust mechanism of Qinghai-Xizang plateau toward NE direction. This paper summarizes the research results of Elm mountain area since recent 20 years from three aspects: fault slip rate, paleoseismic activity habit and tectonic deformation. Through the methods of remote sensing image interpretation, field geological survey, fault dislocation measurement and geomorphologic age determination, the thrust slip rate of the typical dislocation point on the northern margin of Elm Mountain is estimated to be (0.55 ± 0.15) mm / a. The left-lateral slip rate was (0.95 ± 0.11) mm / a. It is thought that the “camel steep ridge” proposed by the predecessor is not the product of the fault activity but the remnant of the ancient diversion project or irrigation and irrigation project, that is, it is not the rupture of the surface earthquakes in AD 180. Based on the mountain morphology reflected by the DEM profile and combining the characteristics of the faults, it is considered that the Yumugu uplift is the result of Qilian thrusting toward N, and the fault activity is still concentrated on the north side of Yumu Mountain. The shape of the mountain body is controlled by the expansion of the fault and extension of the mountain range Is a vertical and lateral process, since the late Cenozoic Yushan continued uplift.