The early stages of continental rifting are accommodated by the growth of upper crustal normal fault systems that are distributed relatively evenly across the rift width. Numerous fault systems define fault arrays, the kinematics of which are poorly understood due to a lack of regional studies drawing on high‐quality subsurface data. Here we investigate the long‐term (~150 Myr) growth of a rift‐related fault array in the East Shetland Basin, northern North Sea, using a regionally extensive subsurface data set comprising 2‐D and 3‐D seismic reflection surveys and 107 boreholes. We show that rift‐related strain during the pre‐Triassic to Middle Triassic was originally distributed across several subbasins. The Middle to Late Triassic saw a decrease in extension rate (~14 m/Myr) as strain localized in the western part of the basin. Early Jurassic strain initially migrated eastward, before becoming more diffuse during the main, Middle‐to‐Late Jurassic rift phase. The highest extension rates (~89 m/Myr) corresponded with the main rift event in the East Shetland Basin, before focusing of strain within the rift axis and ultimate abandonment of the East Shetland Basin in the Early Cretaceous. We also demonstrate marked spatial variations in timing and magnitude of slip along strike of major fault systems during this protracted rift event. Our results imply that strain migration patterns and extension rates during the initial, prebreakup phase of continental rifting may be more complex than previously thought; this reflects temporal and spatial changes in both thermal and mechanical properties of the lithosphere, in addition to varying extension rates.

中文翻译：

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复杂应变划分和非均质延伸率定义的北海北部破裂前延伸

大陆裂谷的早期阶段是由上地壳正断层系统的生长提供的，该断层在裂谷宽度上相对均匀地分布。众多故障系统定义故障阵列，由于缺乏使用高质量地下数据的区域性研究，因此对其运动学的了解甚少。在这里，我们使用包含2D和3D地震反射勘测的区域广泛的地下数据集，以及107个地震，研究了北海北部东设得兰群岛裂谷相关断层阵列的长期（〜150 Myr）增长。钻孔。我们表明，从三叠纪到中三叠纪，与裂谷有关的应变最初分布在几个子盆地。中三叠纪至晚期三叠纪的扩张速率下降（〜14 m / Myr），这是由于该盆地西部的局部应变所致。侏罗纪早期应变最初向东迁移，然后在侏罗纪中晚期至主要裂谷期变得更加分散。最高的扩张速率（〜89 m / Myr）与东设得兰盆地的主要裂谷事件相对应，然后才将应变集中在裂谷轴内，并最终弃绝了白垩纪东设得兰盆地。我们还证明了在这一旷日持久的裂谷事件中，沿主要断层系统走向的时间和滑动幅度的明显空间变化。我们的结果表明，大陆裂谷初始，破裂前阶段的应变迁移模式和扩展速率可能比以前认为的要复杂。除了变化的扩展速率外，这反映了岩石圈热力学性质的时空变化。我们还证明了在这一旷日持久的裂谷事件中，沿主要断层系统走向的时间和滑动幅度的明显空间变化。我们的结果表明，大陆裂谷初始，破裂前阶段的应变迁移模式和扩展速率可能比以前认为的要复杂。除了变化的扩展速率外，这反映了岩石圈热力学性质的时空变化。我们还证明了在这一旷日持久的裂谷事件中，沿主要断层系统走向的时间和滑动幅度的明显空间变化。我们的结果表明，大陆裂谷初始，破裂前阶段的应变迁移模式和扩展速率可能比以前认为的要复杂。除了变化的扩展速率外，这反映了岩石圈热力学性质的时空变化。