Abstract Well-exposed normal fault networks in the Plio-Quaternary sedimentary series of the Zanjan Depression, Iran, were studied in order to analyse the spatial relationships and evolution of fault and damage zone structures in low-burial (~200 m) conditions. Despite the poorly-consolidated, geologically young nature of sediment, fault networks show several characteristics more typical of faulting in lithified strata. Key controls on the evolution of fault networks are found to be fault interactions, segment linkage, and the mechanical stratigraphy resulting in dip refraction, fault segmentation, the development of fault bends and steps, vertical fault overlap zone breaching, and bed-parallel slip. The data show a decrease of fracture frequency away from the fault cores. The obtained data show that damage zones width increases with fault displacement in a non-linear manner. Furthermore, damage zones appear more deformed and wider in the hanging-wall than in the footwall. A plot of damage zone width versus total fault throw reveals a positive but non-linear correlation, and the best-fit function corresponds better to a power-law relationship. The relationship between displacement and length shows a sub-vertical growth path with large displacement gradients typical of faulting in partially-lithified strata, due to shale ductility accommodating fault tip-related strains. A model for the evolution of the normal fault system is proposed based on spatial distribution of deformation, particularly fault segmentation, segment linkage, and damage zone development, as influenced by initial fault spacing, mechanical stratigraphy and the low burial conditions.

中文翻译：

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Plio-第四纪沉积系列中的正断层网络及其空间关系：以伊朗西北部赞詹坳陷为例

摘要 为了分析低埋藏（~200 m）条件下断层和损伤带结构的空间关系和演化，研究了伊朗赞詹坳陷的上新-第四纪沉积系列中出露良好的正断层网络。尽管沉积物固结差，地质年代较年轻，但断层网络显示出几个在岩化地层中更典型的断层特征。发现断层网络演化的关键控制因素是断层相互作用、段联动和机械地层导致倾角折射、断层分割、断层弯曲和台阶的发展、垂直断层重叠带破裂和平行床滑动。数据显示远离断层核心的断裂频率降低。所得数据表明，损伤带宽度随断层位移呈非线性增加。此外，与下盘相比，上盘中的损坏区域看起来更变形且更宽。损坏区宽度与总断层的关系图显示出正但非线性的相关性，并且最佳拟合函数更符合幂律关系。由于页岩延展性适应断层尖端相关应变，位移和长度之间的关系显示了具有大位移梯度的亚垂直增长路径，这是部分岩化地层中典型的断层作用。根据初始断层间距的影响，基于变形空间分布，特别是断层分割、段连接和损伤带发展，提出了正断层系统演化模型，