Abstract: Qilian Shan-Hexi Corridor is located in the northeastern margin of the Tibetan plateau, which hosts many active strike-slip and thrust faults as well as folds. Previous study on this area was mostly concerned with large faults at the boundary of the corridor, while rare work on active tectonics in the interior of the corridor. On 25 October 2003, the Minle-Shandan M_S6.1 earthquake occurred in this area, which is related with the Minle-Yongchang fault hidden beneath the south piedmont of the Dahuangshan Mountains. As there is no obvious rupture trace on the surface, the quantitative study of this fault has never been reported so far.
In order to obtain quantitative parameters of this active structure efficiently, the software of ERDAS was used to generate pointscloud data from SPOT6 stereo-pair. Two-meter resolution DEM imagery from point cloud has the line accuracy of height about 1m. Three swath profiles were extracted from the DEM data, which show that high geomorphic surfaces are all uplifted and folded. By differential GPS measurement, the vertical uplift of the thrust-related fold is estimated to be about 2.0m on the T₂, and the strike of the fold deformation is nearly 311°, which is close to the result of the fault parameter determined by aftershocks, and also in agreement with the focal mechanism solutions. Furthermore, the location of fold axial zone is consistent with the actual investigation data. These indicate that there is obvious tectonic deformation in the west part of the Minle-Yongchang fault. It supports the view that this fault is the seismogenic structure of the 2003 Minle-Shandan earthquake. Stereo-pair is of high importance in active tectonics research, which can provide significant guidance for field geologic investigations and determining the location of tectonic deformation, according to this research.

Key words: Concealed Fault, Stereo-pair, DEM, Characteristics of surface deformation

摘要： 为高效获取民乐-永昌断裂西段活动构造研究的定量参数，利用ERDAS软件，基于SPOT6立体像对提取高分辨率点云数据，经过滤波和插值生成2m分辨率的数字高程模型（DEM）；DEM数据线性高程精度达1m。基于DEM数据提取的高地貌面上的3条廊带剖面显示，区域存在明显的褶皱变形，后续通过高精度差分GPS实测河流阶地纵剖面进一步揭示T₂阶地存在高度约2.0m的构造抬升。廊带剖面和河流阶地纵剖面显示断裂-褶皱变形整体走向为311°，与小震精定位反演拟合断层参数和震源机制解结果相近，其位置也与地震应急科考资料显示现场情况吻合。上述结果表明，民乐-永昌隐伏断裂西段民乐—大马营段存在明显的构造变形，支持该断裂为2003年民乐-山丹M_S6.1和5.8级地震发震断层的认识。立体像对对于活动构造研究具有重要的作用，可为室内确定构造变形的空间位置和野外详细考察提供重要指导。

关键词: 隐伏断裂, SPOT6立体像对, DEM, 构造变形特征