Structural Inheritance in active and ancient extensional regimes

构造继承性是受断裂带动态、长期弱化控制的大陆岩石圈变形的特征。许多伸展盆地和大陆边缘显示出在其早期阶段受到先前存在的结构和组构(构造继承)的强烈影响的证据，然后随着盆地边界断层的增长和相互作用以及裂谷作用的成熟而下降。这种重组是如何发生的，其控制机制(S)以及对活动区盆地充填和地震活动模式的影响尚不清楚，这是本博士研究项目的主题。沉积体系中的构造继承被归因于1)先前存在的断层和组构的直接重新激活，2)区域应力场的局部扰动，导致断层以非最佳方向形成或重新激活，(3)基底块体或盆地岩浆扇区对正断层阵列生长的分割和延缓。本项目的目的是利用构造、地球物理和模拟相结合的方法，研究是什么控制了伸展盆地从继承性为主到远场应力为主的变形。具体的焦点将放在代表处于结构重组阶段的系统的例子上，或者在这些例子中，轴线-平行断层和受离轴基底影响的结构叠加，但仍然可见。西格陵兰、坦桑尼亚东非裂谷、中国西北部的鄂尔多斯裂谷和意大利的亚平宁裂谷是主要的研究区域，但这些特征是大多数边缘和盆地所共有的。利用地球物理、大地测量和野外观测得出的数据集，约束活动伸展盆地中基底继承成分的性质。使用现有的地震反射数据建立同裂谷盆地充填的内插，以限制构造重组过程的性质和时间。使用数值模拟研究从地幔岩石圈的结构重组到地壳尺度的控制和地震危害。该项目将使学生有机会获得基于现场的构造地质学、活动构造、地震解释和数值模拟方面的技能。

Structural inheritance is a characteristic of continental lithosphere deformation controlled by dynamic and long-term weakening of fault zones. Many extensional basins and continental margins show evidence for a strong influence by pre-existing structures and fabrics (structural inheritance) during their early phase that then declines as basin boundary faults grow and interact and rifting matures. How this reorganisation occurs, the controlling mechanism(s) and effects on basin fills and seismicity patterns in active regions is not well under understood and is the topic for this PhD research project.Structural inheritance in sedimentary systems has been attributed to 1) direct reactivation of pre-existing faults and fabrics, 2) local perturbations of regional stress fields which causes faults to form or reactivate in non-optimal orientations, (transverse or - off-axial trend faults) and 3) segmentation and retardation of normal fault array growth either by basement blocks or magmatic sectors in basins.The aim of this project is to investigate what controls the transition from inheritance-dominated to far-field stress-dominated deformation in extensional basins using a combined structural, geophysical and modelling approach. The specific focus will be on examples that represent systems in the structural reorganisation phase or where the axis-parallel faults and off-axis basement-influenced structures are superimposed but remain visible. Candidate faults (with off-axis orientations) are located in the West Greenland, East Africa Rift in Tanzania, the Ordos rifts in NW China and the Italian Apennines, which form the main study areas, however these features are common to most margins and basins.The study objectives are to:-1. Constrain the nature of basement inheritance components in active extensional basins using geophysical, geodetic and field-observation derived datasets.2. Build interpolations of syn-rift basin fills using available seismic reflection data to constrain the nature and timing of structural reorganisation processes.3. Investigate the controls and seismic hazard implications from structural reorganisation at mantle lithosphere to crustal scales using numerical simulations.The project will give the student an opportunity to gain skills in field-based structural geology, active tectonics, seismic interpretation and numerical modelling.