We present crustal scale physical analogue models of multiphase rifting to provide new constraints on the role exerted by faults formed during early extension on structures developed during later episodes of rifting. Our laboratory experiments (sand mixture is used to simulate the upper crust and PDMS-Corundum mixture is used to simulate the lower crust) are inspired by the Turkana depression in the East African Rift System, a natural case of rift zone developed through multiple extensional phases. The models reproduce a first rifting phase with NE-SW extension direction followed by a phase of W-E trending extension. In the experiments, we varied the amount of extension during the initial phase, which caused variations in the development and prominence of sets NW-SE normal faults, representing pre-existing faults to be potentially reactivated during the later rifting phase. Our model results indicate that the amount of extension in the early phase is critical in controlling the reactivation: the greater the amount of extension in the 1st-phase, the more important early faults are, and the easier these 1st-phase normal faults are reactivated during the 2nd-phase. At a local scale, fault reactivation may result in faults with a typical zigzag pattern, whose importance increases with the increase in the amount of extension during the early phase. Extrapolation of model results to the Turkana depression suggests that large-scale fault reactivation is unlikely to have occurred in the region, possibly implying that the Cretaceous-Early Paleogene extension was limited in the central part of Turkana depression. Results have been also extrapolated to other regions interested by multiphase rifting, such as basins in the North Sea rift.

我们提出多阶段裂谷的地壳尺度物理模拟模型，以提供对在早期裂谷后期发展的构造上早期伸展形成的断层所施加的作用的新约束。我们的实验室实验（砂混合物用于模拟上地壳，PDMS-刚玉混合物用于模拟下地壳）受到东非裂谷系统中图尔卡纳洼地的启发，东非裂谷系统是裂谷带经过多个伸展阶段而形成的自然情况。这些模型再现了NE-SW扩展方向的第一个裂谷阶段，随后是WE趋势扩展的阶段。在实验中，我们改变了初始阶段的扩展量，这导致了NW-SE组正常断层的发育和突出程度的变化，表示先前存在的断层可能在随后的裂谷阶段被重新激活。我们的模型结果表明，早期阶段的扩展量对于控制重新激活至关重要：第一阶段的扩展量越大，早期故障越重要，并且这些第一阶段的正常故障越容易被重新激活。在第二阶段。在局部范围内，断层重新激活可能会导致断层呈典型的锯齿形，其重要性随着早期阶段扩展量的增加而增加。将模型结果外推到图尔卡纳depression陷表明该地区不太可能发生大规模断层再活化，这可能意味着在图尔卡纳depression陷的中部白垩纪-早期古近纪扩展受到限制。