3D Numerical Modelling of Large, Rapid, Violent Geologic Processes

陨石撞击、大型长期滑坡、火山崩塌、海底滑坡以及此类事件在海洋环境中发生时产生的海啸，是一系列大型、快速、剧烈的地质过程的一部分，可能会造成灾难性后果。公众对这些现象的认识很高，但我们对它们的基本认识还远远不够。这在很大程度上是因为这样的高能过程是不可能在实验室规模上模拟的，而且到目前为止，它们的数值模拟既困难又昂贵。拟议研究的目的是开发一种先进的3D数值模型，用于模拟撞击和其他剧烈的地质过程，并使用该模型来调查知之甚少的陨石撞击、大型空中和海底滑坡以及撞击和崩塌产生的海啸等自然灾害，预测它们的行为，并最终帮助减轻它们的破坏性后果。近年来，撞击坑已经成为影响地球和生命进化的一个重要过程。现在人们认为，撞击至少造成了一次大灭绝，形成了月球，并可能为原始生命创造了栖息地，并通过近地表岩石的高速喷射，导致生命在太阳系内的转移。撞击坑在地球历史上的灾难性作用及其深远的后果，使我们迫切需要了解撞击及其所造成的危害。然而，我们对撞击过程的了解仍然存在根本性的差距。我们目前的理解绝大多数来自模型和实验，其中目标材料是均匀的，撞击器垂直于目标表面。实际上，这样的事件在地球上是极不可能发生的；斜向撞击比近垂直撞击要常见得多，而且地球上几乎没有一个地方的近地下是均匀的（例如，地球表面的70%被水覆盖）。对于撞击器轨迹与目标表面的角度以及目标表面成分和强度的变化对撞击过程的影响，人们知之甚少。实验室实验和初步的建模工作表明，这两个因素可能会大大改变陨石坑的大小和形状，以及在撞击过程中形成的危险的热蒸发岩石的数量，但需要复杂的3D建模来完全量化影响。在这项工作中，将进行必要的撞击模拟，以确定任何大小的小行星或彗星以任何速度和角度撞击地球的环境后果，并进入任何类型的目标表面。另外两个鲜为人知的地质过程，要么是撞击的直接后果，要么涉及类似的物理过程，是由滑坡或撞击引起的大型岩石雪崩和海啸。大型岩石雪崩在水平方向上移动的距离很大，而垂直方向上的高度下降幅度相对较小。它们的迅速移动和广泛传播使它们成为一种重大的自然灾害，尽管它们很少发生。然而，它们高流动性的物理解释尚未被确定，因此没有可靠的模型来预测它们的行为。水下滑坡和海洋撞击事件可能引发一种局部海啸，具有高上升率和潜在的破坏性后果。然而，这些波浪的产生、传播和破裂尚不清楚，这导致了对这类海啸所造成的危害的截然不同的看法。作为这项研究的一部分开发的模型也将用于模拟这些过程。这些模型将用于研究大型岩石雪崩为何能比小型雪崩移动得更远，并重新评估滑坡和海啸的危害。

Meteorite impacts, large long-runout landslides, volcanic collapse, submarine landslip, and the tsunamis generated when such events occur in a marine environment, are part of a family of large, rapid, violent geologic processes that have potentially catastrophic consequences. Public awareness of these phenomena is high, but our fundamental understanding of them is far from complete. This is in large part because such high-energy processes are impossible to simulate on the laboratory scale and they have been difficult and expensive to simulate numerically until now. The aim of the proposed research is to develop an advanced, 3D numerical model for simulating impacts and other violent geologic processes, and to use this model to investigate the poorly understood natural hazards of meteorite impact, large sub-aerial and sub-marine landslip, and impact- and collapse-generated tsunamis, to predict their behaviour, and ultimately to help mitigate their destructive consequences. In recent times, impact cratering has emerged as an influential process in the evolution of the Earth and life as it exists today. It is now believed that impacts caused at least one mass-extinction, the formation of the moon, and possibly created habitats for primitive life and caused the transfer of life across the solar system, via the high-speed ejection of near-surface rocks. The catastrophic role of impact cratering in Earth history and its far-reaching consequences make imperative the need to understand impacts and the hazard that they pose. However, fundamental gaps remain in our knowledge of the impact process. The vast majority of our current understanding is derived from models and experiments where the target material is uniform and the impactor strikes perpendicular to the target surface. In reality, such events are extremely unlikely to occur on Earth; oblique impacts are far more common than near-vertical impacts, and almost nowhere on the Earth can its near-subsurface be considered uniform (for example, 70% of the Earth's surface is covered by water). The effect on the cratering process of the angle of the impactor's trajectory to the target surface, and variations in the composition and strength of the target surface, are poorly understood. Laboratory experiments and preliminary modelling work suggest that both these factors may change substantially the size and shape of the crater, and the amount of hazardous, hot vaporised rock formed during an impact, but sophisticated 3D modelling is required to fully quantify the effects. In this work the necessary impact simulations will be performed to determine the environmental consequences of impacts on Earth for any size asteroid or comet, at any velocity and angle and into any type of target surface. Two other poorly understood geologic processes that are either an immediate consequence of impacts, or involve similar physical processes, are large rock avalanches and tsunamis generated by landslides or impacts. Large rock avalanches travel vast horizontal distances with only a comparatively small vertical drop in height. Their rapid movement and extensive reach makes them a significant natural hazard, despite the rarity of their occurrence. However, the physical explanation for their high mobility has not yet been ascertained, and hence no reliable model exists for predicting their behaviour. Underwater landslides and oceanic impact events can trigger a type of local tsunami with high run-up and potentially devastating consequences. However, the generation, propagation and breaking of these waves are not yet understood, which has led to wildly differing views on the hazard that these types of tsunamis pose. The model developed as part of this research will also be adapted to simulate these processes. The models will be used to investigate how large rock avalanches can travel so much further than small ones, and to reassess the landslide- and impact-tsunami hazard.