Modeling of the Dec. 22nd 2018 Anak Krakatau volcano lateral collapse and tsunami based on recent field surveys: Comparison with observed tsunami impact
Modeling of the Dec. 22nd 2018 Anak Krakatau volcano lateral collapse and tsunami based on recent field surveys: Comparison with observed tsunami impact
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DOI：
10.1016/j.margeo.2021.106566
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发表时间：
2021-10
期刊：
影响因子：
2.9
通讯作者：
S. Grilli;Cheng Zhang;J. Kirby;A. Grilli;D. Tappin;S. Watt;J. Hunt;A. Novellino;S. Engwell;Muhammad Edo Marshal Nurshal;M. Abdurrachman;M. Cassidy;A. Madden-nadeau;S. Day
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作者：
S. Grilli;Cheng Zhang;J. Kirby;A. Grilli;D. Tappin;S. Watt;J. Hunt;A. Novellino;S. Engwell;Muhammad Edo Marshal Nurshal;M. Abdurrachman;M. Cassidy;A. Madden-nadeau;S. Day
2018年12月22日，印度尼西亚巽他海峡的Anak Krakatau（AK）火山的侧向坍塌将火山碎屑物质排入火山西南部250米深的破火山口，并产生了大海啸，导致近场高达85米，远场高达13.5米，苏门答腊和爪哇附近海岸。海啸造成437人死亡，这是自1883年喀拉喀托火山爆发和1888年里特岛扇形崩塌以来，火山引发的海啸造成的最大死亡人数。100多年来，2018年的AK事件首次提供了一个机会来研究一场造成广泛生命损失和重大破坏的大型火山海啸。在这里，我们使用最先进的数值模型对崩塌和海啸的产生、传播和海岸影响进行了数值模拟，使用了崩塌的新参数化和基于我们2019年实地调查和卫星图像的近场测深数据集。这些陆上和海底的数据集被用来约束滑坡机制的几何形状和规模，这表明，主要的滑坡疤痕平分AK editarian，中央通风口后切割，并删除其陆上体积的50%。主要滑坡体积估计范围为0.175-0.313立方公里，根据不确定性的形状淹没部分的故障面。这一点得到了对原始滑坡存款体积（0.214 ± 0.036 km 3）的独立估计的支持。由于故障体积的不确定性，我们定义了一系列潜在的故障表面，跨越这些值在4个崩溃的情况下，体积范围从0.175到0.313立方公里。这些AK崩溃建模，假设颗粒或粘性流体流变学，连同其相应的海啸的产生和传播。一个单一的海啸，没有后续波的观测结果，是一致的，我们的解释滑坡故障在一个快速的，单一的运动阶段，而不是一个更零碎的过程，产生海啸，在约30分钟内到达附近的海岸线。对于这两个模型流变学，0.224 km 3的崩溃（第二和首选方案）最成功地再现了近场和远场海啸流的深度和运行中观察到的所有事后现场调查结果，验潮仪记录，和目击者的报告，到目前为止，这表明我们估计的滑坡体积范围是适当的。这一事件突出了相对小规模的侧向火山崩塌所造成的重大危险，这种崩塌可能在没有任何意外信号的情况下发生，是一种有效和不可预测的海啸源。我们成功的模拟表明，目前的数值模型可以准确地预测这些事件的海啸灾害。在Anak Krakatau这样的情况下，由于没有紧急警报信号，加上海啸发生后的旅行时间很短，这对减轻海啸对沿海地区的影响构成了重大挑战，因此必须为这类事件开发和安装预警系统。
The Dec. 22, 2018 lateral collapse of the Anak Krakatau (AK) volcano in the Sunda Straits of Indonesia discharged volcaniclastic material into the 250 m deep caldera southwest of the volcano and generated a large tsunami, causing runups of up to 85 m in the near-field, and 13.5 m in the far-field, on the nearby coasts of Sumatra and Java. The tsunami caused 437 fatalities, the greatest number from a volcanically-induced tsunami since the catastrophic explosive caldera-forming eruption of Krakatau in 1883 and the sector collapse of Ritter Island in 1888. For the first time in over 100 years, the 2018 AK event provides an opportunity to study a major volcanically-generated tsunami that caused widespread loss of life and significant damage. Here, we present numerical simulations of the collapse and tsunami generation, propagation, and coastal impact, with state-of the-art numerical models, using both a new parametrization of the collapse and a near-field bathymetric dataset based on our 2019 field surveys and satellite images. These subaerial and submarine data sets are used to constrain the geometry and magnitude of the landslide mechanism, which show that the primary landslide scar bisected the AK edifice, cutting behind the central vent and removing 50% of its subaerial volume. The primary landslide volume is estimated to range from 0.175–0.313 km3, based on uncertainties in the shape of the submerged part of the failure plane. This is supported by an independent estimate of the primary landslide deposit volume of 0.214 ± 0.036 km3. Given uncertainties in the failure volume, we define a range of potential failure surfaces that span these values in 4 collapse scenarios of volume ranging from 0.175 to 0.313 km3. These AK collapses are modeled, assuming either a granular or viscous fluid rheology, together with their corresponding tsunami generation and propagation. Observations of a single tsunami, with no subsequent waves, are consistent with our interpretation of landslide failure in a rapid, single phase of movement rather than a more piecemeal process, generating a tsunami which reached nearby coastlines within ~30 min. For both modeled rheologies, the 0.224 km3collapse (second and preferred scenario) most successfully reproduces the near- and far-field tsunami flow depth and runup observed in all post-event field survey results, tide gauge records, and eyewitness reports to date, suggesting our estimated landslide volume range is appropriate. This event highlights the significant hazard posed by relatively small-scale lateral volcanic collapses, which can occuren-masse, without any precursory signals, and are an efficient and unpredictable tsunami source. Our successful simulations demonstrate that current numerical models can accurately forecast tsunami hazards from these events. In cases such as Anak Krakatau's, the absence of precursory warning signals, together with the short travel time following tsunami initiation present a major challenge for mitigating tsunami coastal impact, stressing the need to develop and install early warning systems for such events.