NSFGEO-NERC Caldera-forming eruption-generated tsunamis

海啸对人口稠密的沿海地区造成重大地质灾害，减轻这种灾害需要了解其产生机制。海啸产生和传播的数值模型用于支持预警系统和制作洪水地图，以便进行危害评估。海啸可归因于地震（即地震和海底滑坡）或非地震源（即火山爆发）。后者在世界各地的一些地区普遍存在（例如，美国西海岸的阿留申弧）。我们对海啸产生机制的理解，如地震、山体滑坡和火山崩塌，主要是由破坏性事件（例如，巴布亚新几内亚，1998年；印度洋，2004年；日本，2011年）造成的，这些事件共造成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（本研究的重点）在很大程度上仍未得到充分研究。在这项多学科研究中，美国/英国团队将进行协作实地和建模研究，以提高我们对火山爆发产生的海啸的理解，特别是那些来自靠近海洋的大容量火山口形成事件的海啸，这是最具破坏性的地质灾害之一。工作重点将放在1883年喀拉喀托火山爆发引发的海啸上，那次海啸在印度尼西亚造成3.3万多人死亡。尽管人们对这次火山喷发进行了充分的研究，但关于海啸产生的机制仍然存在争议。自1883年以来，除了在火山喷发100周年之际引起的兴趣激增外，几乎没有新的数据，而这些数据将成为研究该事件的主要项目的基础。该项目产生的新认识/模型将改进来自这些震源的海啸灾害评估和预警，并可以改进作为非震源海啸预警系统的海啸灾害评估和淹没测绘工作，这对人口安全具有重要意义。项目结果将通过专业会议、同行评议期刊、建立一个广泛的网站（包含项目元数据、新闻、播客/视频和辅助信息）以及通过科学数据的可视化（针对K-12受众）向科学界和更广泛的社区传播。一开始将在印度尼西亚组织一个讲习班，让当地人民和科学家参与（正在寻求牛顿基金的支持）。将与面临类似爆发海啸风险的希腊/加勒比/地中海机构/组织的同事积极合作。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的历史事件（如3500BP的圣托里尼和7500BP的Kikai）的代表，并包括多种海啸产生机制：火山碎屑密度流（PDC）向海洋排放、火山口崩塌和爆炸。从当时的观测来看，它也有异常的喷发和海啸记录。研究的目的是：1)应用改进的火山喷发机制（包括海底沉积物）海啸数值模型，主要是PDC和破火山口崩塌；2)对陆地海啸沉积物进行新的实地调查，以区分个别海啸事件及其影响；3)进行新的PDC现场调查，补充海上试验地震数据库，表明可以识别和绘制单个PDC流动，并估计其波动和体积；4)利用这些估计值来了解PDCs进入海洋后的物理性质；5)利用新的资料（沉积物、PDC）作为应用新的海啸数值模式的基础。海啸模拟将通过将模型输出（淹没极限、累积量、PDC沉积/累积量）与苏门答腊和爪哇沿岸受影响地区的历史文献以及新旧获得的PDC和沉积物沉积实地调查数据进行比较，反复进行。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Tsunamis create major geohazards for populated coastal areas, whose mitigation requires understanding of the generation mechanisms. Numerical models of tsunami generation and propagations are used in support of warning systems and for the creation of inundation maps for hazard assessment. Tsunamis can be attributed to seismic (i.e., earthquakes and submarine landslides) or non-seismic sources (i.e., volcanic eruptions). The latter are prevalent in some areas around the world (e.g., Aleutian arc for US West Coast). Our understanding of tsunami generation from mechanisms such as earthquakes, landslides, and volcanic collapse, has largely resulted from devastating events (e.g., Papua New Guinea, 1998; Indian Ocean, 2004; Japan, 2011), which combined have caused over 300,000 fatalities and US $30B of damage. Due to lack of a major recent event, eruption generated tsunamis (the focus of this study) remain largely under-studied. In this multi-disciplinary study, the US/UK team will perform collaborative field and modeling research, to improve our understanding of tsunamis generated by volcanic eruptions, especially those from large-volume, caldera-forming events close to the sea, which are among the most devastating geohazards. Work will focus on the 1883 Krakatau eruption-generated tsunami, which caused over 33,000 fatalities in Indonesia. Although this eruption was well studied, there is still controversy over the tsunami generation mechanism and, since 1883, apart from a surge of interest during its 100-year anniversary, there has been little new data, which would be a basis for a major project on the event. The new understanding/modeling resulting from this project will improve tsunami hazard assessment and warning from such sources, and could improve operational tsunami hazard assessment and inundation mapping work as tsunami warning systems for non-seismic sources with significant implication in population safety. Project results will be disseminated to the scientific and broader communities at professional conferences, in peer-reviewed journals, by building an extensive website (with project metadata, news, podcasts/videos, and auxiliary information), and through the visualization of scientific data (targeting a K-12 audience). A workshop will be organized in Indonesia at the outset to engage local people and scientists (support from Newton funds is being sought). There will be active collaboration with colleagues at Greek/Caribbean/Mediterranean-based institutions/organizations, facing similar eruption-tsunami risks.As a large-volume, caldera-forming event Krakatau is representative of similar other well studied historical events (e.g., 3500BP Santorini and 7500BP Kikai), and includes diverse tsunami generating mechanisms: pyroclastic density current (PDC) discharges into the sea, caldera collapse, and explosions. It also has an exceptional eruption and tsunami record from observations at the time. The objectives of the study are to: 1) apply improved numerical models of tsunamis from volcanic eruption mechanisms (including seafloor deposits), mainly PDC and caldera collapse; 2) perform new field surveys of on land tsunami sediment deposits, to discriminate individual tsunami events and their impact; 3) perform new PDC field surveys, complementing a pilot offshore seismic database showing that individual PDC flows can be identified and mapped, and their runouts and volumes estimated; 4) use these estimates to understand physical properties of PDCs as they enter the sea; and 5) use the new data (sediment, PDC) as a basis for applying the new numerical tsunami models. Tsunami simulations will be carried out iteratively by comparing model outputs (inundation limits, runups; PDC deposits/runouts) with historical documentation of impacted areas along the coasts of Sumatra and Java, and both old and newly acquired PDC and sediment deposit field survey data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.