NSFGEO-NERC: Tsunamis from large volume eruptions

历史上由火山喷发引发的海啸造成的最大生命损失发生在1883年印度尼西亚喀拉喀托火山爆发时。在这次大规模的火山口形成事件中，火山引发的多次海啸袭击了爪哇岛和苏门答腊岛的邻近海岸，造成大约3.3万人死亡。提出的海啸产生机制包括火山碎屑密度流产生的崩塌喷发柱，爆炸，火山口崩塌和横向爆炸。然而，尽管发表了许多关于这些机制对海啸的相对贡献的论文，但它们仍然没有被清楚地识别或定义，并且在130多年来一直是猜测和争议的来源。在这项多学科的研究中，对喀拉喀托火山的研究将提高我们对火山爆发引起的海啸的理解，特别是那些来自大容量火山口形成事件的海啸，因为它们靠近海洋，有可能产生毁灭性的海啸。作为一个大体积的火山口形成事件，喀拉喀托火山是其他类似例子的代表，如3500 BP的圣托里尼（爱琴海南部）和7500 BP的Kikai（日本）。像这些更古老的史前事件一样，喀拉喀托火山爆发包括多种海啸产生机制，包括火山碎屑密度流（PDC）向海洋排放、火山口崩塌和爆炸。将喀拉喀托火山列为最值得研究的事件的一个关键方面是Verbeek在火山爆发后立即进行的事后调查，该调查描述了火山爆发以及火山爆发和海啸的影响。这些描述为新的海啸数值模拟提供了验证，这是任何其他类似事件所没有的。这项研究的更广泛背景是，对其他机制（如地震、山体滑坡和火山崩塌）引发海啸的新认识，在很大程度上源于最近的破坏性事件，如1998年的巴布亚新几内亚、2004年的印度洋和2011年的日本。这些事件已造成30多万人死亡和300亿美元的损失。由于缺乏近期的重大事件，火山喷发引发的海啸在很大程度上仍未得到研究。因此，这个多学科项目将解决海啸产生的非地震机制方面的一个主要知识缺口——火山爆发引发的海啸。确定喷发机制及其在海啸产生中的相对贡献对于开发可靠的海啸数值模型至关重要。因此，第一个挑战是确定最可能的海啸机制。尽管这些机制存在不确定性，但最有可能的是火山口崩塌和火山碎屑密度流（PDCs）进入海洋。要确定支撑海啸模型的机制，还有许多其他挑战。火山PDC沉积和火山口崩塌将在喀拉喀托岛周围的海洋调查中绘制出来。将会有新的数值模拟火山碎屑密度流是如何进入海洋的，以及火山碎屑密度流和火山口崩塌产生海啸的新数值模型。海啸数值模型将通过实地工作来验证，以研究海啸淹没海岸时沉积的沉积物。

The greatest loss of life from any historic volcanic eruption-generated tsunami was in 1883 when the Krakatau volcano in Indonesia erupted. During this large-volume, caldera-forming event, multiple, volcanically-triggered tsunamis were generated which, on striking the adjacent coasts of Java and Sumatra, killed approximately 33,000 people. The proposed tsunami generation mechanisms include pyroclastic density flows produced from collapsing eruption columns, explosions, caldera collapse and a lateral blast. Yet, despite numerous published papers on the relative contributions to the tsunami from these mechanisms, they are still not clearly identified or defined, and have been a source of speculation and controversy for over 130 years. In this multi-disciplinary study, the research on the Krakatau will improve our understanding of tsunamis generated by volcanic eruptions, especially those from large-volume, caldera-forming events which, because of their proximity to the sea, have the potential to generate devastating tsunamis. As a large-volume, caldera-forming event Krakatau is representative of other, similar examples, such as Santorini (southern Aegean) in 3500 BP and Kikai (Japan) in 7500 BP. Like these older, prehistoric events, the Krakatau eruption includes diverse tsunami generating mechanisms including pyroclastic density current (PDC) discharges into the sea, caldera collapse, and explosions. One of the critical aspects of Krakatau, which single it out as the best event to study is the post event survey carried out immediately after the eruption by Verbeek, which describes the eruption and the impact of the eruption and tsunami. These descriptions provide validation of the new numerical tsunami modelling, which is not available from any other analogous event. The broader background to the research is that new understandings of tsunami generation from other mechanisms, such as earthquakes, landslides, and volcanic collapse, has largely resulted from recent devastating events, such as Papua New Guinea, 1998, the Indian Ocean, 2004, and Japan, 2011. These events have caused over 300,000 fatalities and US$30 billion of damage. Due to the lack of a major recent event, eruption generated tsunamis remain largely unresearched. This multidisciplinary project therefore, will address a major knowledge gap in non-seismic mechanisms of tsunami generation - tsunamis from volcanic eruptions. Defining eruption mechanisms and their relative contributions in tsunami generation is essential to the development of robust numerical tsunami models. The first challenge, therefore is to identify the most likely tsunami mechanisms. Although, there is uncertainty over these mechanisms, the most likely are caldera collapse and the entry into the sea of pyroclastic density currents (PDCs). To identify the mechanisms that underpin the tsunami models there are number of additional challenges. The volcanic PDC deposits and the caldera collapse will be mapped out during a marine survey around Krakatau Island. There will be new numerical modelling of how pyroclastic density currents enter the sea and new numerical models of tsunami generation from pyroclastic density flows and caldera collapse. The numerical tsunami models will be validated by field work to research sediments deposited as the tsunami flooded the coast.