Faulting and folding of basement rocks together accommodate convergence within continental orogens, forming complex zones of intraplate deformation shaped by the fault interaction. Here we use the river terraces along the Dongda river to examine the tectonic deformation patterns of the hinterland and the foreland of the eastern North Qilian Shan, a zone of crustal shortening located at the northeast margin of the Tibetan Plateau. Five Late Pleistocene–Holocene terraces of Dongda river are displaced by three major reverse faults: Minle-Damaying fault, Huangcheng-Ta'erzhuang fault, and Fengle fault, from south to north. Based on displaced terrace treads, we estimated vertical slip rates along the Minle-Damaying fault as 0.7–0.8 mm/a, and along the Fengle fault as 0.5–0.7 mm/a. Deformed terraces suggest an additional uplift of ∼0.2 mm/a through the folding of the Dahuang Shan anticline. Inhomogeneous uplift of the intermontane basins between the Minle-Damaying fault and the Dahuang Shan anticline indicates a 0.9 ± 0.2 mm/a uplift rate along the Huangcheng-Ta'erzhuang fault. Kinematic modeling of this thrust system shows that deformation propagated northward toward the foreland along a south-dipping 10° décollement rooted into the Haiyuan fault at the depth of ∼20 km. This system accommodates 2.7–3.4 mm/a total crustal shortening rate. We suggest this broad thrust belt and the relatively high rate of shortening within this part of the eastern Qilian Shan is a result of the oblique convergence along a restraining bend of Haiyuan fault system. The elevated shortening rate within this area indicates high potential seismic hazard.

中文翻译：

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东北青藏高原东北祁连前沿变形河流阶地断裂相互作用及应变分区推导


基岩的断层和褶皱共同容纳了大陆造山带内的汇合，形成了由断层相互作用形成的复杂的板内变形带。在这里，我们利用东大河沿岸的河流阶地来研究北祁连山东部腹地和前陆的构造变形模式，祁连山是位于青藏高原东北缘的地壳缩短带。东大江 5 个晚更新世—全新世阶地由南向北依次为民乐—大马营断裂、皇城—塔二庄断裂、丰乐断裂 3 条主要逆断层。根据移位的阶地踏面，我们估计沿 Minle-Damaying 断层的垂直滑移速率为 0.7-0.8 mm/a，沿 Fengle 断层的垂直滑移速率为 0.5-0.7 mm/a。变形的梯田表明，通过大黄山背斜的折叠，额外隆起了 ∼0.2 mm/a。民乐—大马营断裂与大黄山背斜之间山间盆地的不均匀隆升表明，皇城—塔尔庄断裂沿线的隆升速率为 0.9 ± 0.2 mm/a。该逆冲系统的运动学模型显示，变形沿着扎根于 ∼20 km 深度的海源断层的南倾 10° 斜坡向前陆向北传播。该系统可容纳 2.7–3.4 mm/a 的总地壳缩短速率。我们认为，祁连山东部这一部分的宽阔逆冲带和相对较高的缩短速率是沿海源断裂系统限制性弯曲的斜向汇合的结果。该区域内较高的缩短率表明潜在的地震危险很高。