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Assessing the accuracy of combined DEM-based lineament mapping and the normalised SL-index as a tool for active fault mapping
Tectonophysics ( IF 2.7 ) Pub Date : 2021-05-24 , DOI: 10.1016/j.tecto.2021.228942
Willem Viveen , Patrice Baby , Christian Hurtado Enriquez

Satellite image-based lineament mapping in combination with the normalised Stream Length Gradient Index (SL/K-index) is one of the most widely used methods to identify active faults in areas where other verification methods, such as faulted strata, geophysical subsurface data, or seismic activity in the upper crust, are unavailable, and to classify their degree of activity. The accuracy of this approach, however, has not yet been assessed rigorously. We assess its accuracy by comparing the results against 27 thrust fault segments that were identified from six seismic reflection profiles with a total length of 340 km. Over 106,000 SL/K points were calculated from 815 river profiles on basis of the SRTM v.3.0 DEM. Standard deviations (SD) of < -2SD (class 1) to > +2SD (class 5) were calculated from the lognormalised SL/K data and five SL/K classes were made and assigned to the nearby lineaments. A comparison with the fault segments from the seismic profiles showed a good coincidence between the presence of knickpoints, SL/K classes 4 and 5 and to a lesser extent class 3. Lineaments with SL/K classes 1 and 2 never corresponded to actual faults. We identified seven master thrusts of which three are very active to highly active, likely older, structures with important amounts of accumulated slip. The other thrusts are probably younger faults with relatively little accumulated slip, yet they are also active to highly active faults. Minor strike-slip faults were identified as very active to highly active structures. Published slip rates shows that at least some of the SL/K class 4 faults experience slip rates of ~1 to ~4 mm a−1 and the SL/K class 5 strike-slip faults may experience slip rates as high as one metre over the course of several months. Most active faults occur where the basal evaporite layer is abnormally thick.



中文翻译:

评估组合基于 DEM 的线性映射和归一化 SL 指数作为活动断层映射工具的准确性

基于卫星图像的线条映射结合归一化的河流长度梯度指数 (SL/K-index) 是在其他验证方法(如断层地层、地球物理地下数据)的地区识别活动断层的最广泛使用的方法之一。或上地壳的地震活动,不可用,并对其活动程度进行分类。然而,这种方法的准确性尚未得到严格评估。我们通过将结果与从 6 个总长 340 公里的地震反射剖面中识别出的 27 个逆冲断层段进行比较来评估其准确性。根据 SRTM v.3.0 DEM,从 815 条河流剖面计算了超过 106,000 个 SL/K 点。< -2SD(第 1 类)到 > 的标准偏差 (SD) +2SD(第 5 类)是从对数归一化 SL/K 数据计算出来的,并且制作了五个 SL/K 类并分配给附近的线条。与来自地震剖面的断层段的比较表明,存在的 SL/K 等级 4 和 5 以及较小程度的等级 3 之间存在良好的一致性。具有 SL/K 等级 1 和 2 的线条从未对应于实际断层。我们确定了七个主推力,其中三个从非常活跃到高度活跃,可能是较旧的结构,具有大量累积滑移。其他逆冲断层可能是较年轻的断层,累积滑移相对较少,但它们对高度活跃的断层也很活跃。小的走滑断层被确定为非常活跃到高度活跃的结构。-1和 SL/K 5 级走滑断层在几个月的过程中可能会经历高达一米的滑移率。最活跃的断层发生在基底蒸发岩层异常厚的地方。

更新日期:2021-05-28
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