Abstract Segmentation, propagation, and linkage of normal faults often occur in regions of active extension, and observations of the distribution and structural properties of segment boundaries can provide important insights for seismic hazard assessment. In this study, we carry out quantitative geomorphological analysis to evaluate the relative tectonic activity along the Langshan Piedmont Fault (LPF), which bounds the NW margin of the Hetao Graben, North China. On the basis of obtained morphometric indices (HI, BS, Smf, VF, SLK, and χ), tectonic knickpoint heights, footwall topography, and small unmanned aerial vehicles (sUAV)-based field observations, we demonstrate that: (i) The Langshan landscape is in a state of disequilibrium in response to active rock uplift and channel incision; (ii) The LPF consists of two major fault segments with lengths of 65 and 95 km, respectively, which likely have been linked with each other; (iii) Rupturing of the whole of one segment can generate an earthquake of M w ~7.3–7.5, and earthquake magnitude may reach M w ~7.8 if the entire fault trace of ~160 km is ruptured, posing a significant seismic risk in the western Hetao Graben. These findings would further our understanding of normal fault evolution through space and time in actively extending regions.

中文翻译：

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华北狼山活动正断层演化的地貌特征

摘要 正断层的分段、传播和连接往往发生在活动伸展区域，对分段边界的分布和结构特性的观察可以为地震危险性评估提供重要的见解。在这项研究中，我们进行了定量地貌分析，以评估沿华北河套地堑西北边缘的狼山山前断裂（LPF）的相对构造活动。根据获得的形态测量指数（HI、BS、Smf、VF、SLK 和 χ）、构造裂点高度、下盘地形和基于小型无人机 (sUAV) 的现场观测，我们证明：狼山景观因岩体活动隆起和河道下切而处于不平衡状态；(ii) LPF 由两个主要断层段组成，长度分别为 65 和 95 公里，很可能已相互连接；(iii) 整个一段断裂可产生 M w ~7.3-7.5 的地震，如果 ~160 km 的整个断层轨迹破裂，地震震级可能达到 M w ~7.8，在该地区构成重大地震风险。河套地堑西部。这些发现将进一步加深我们对活动延伸区域中正断层随空间和时间演化的理解。