Tsunamigenic mass flows at Stromboli Volcano- analysis and modelling after the 3rd of July events

由大规模物质流（在这种情况下称为海啸）产生的海啸，如大型滑坡和火山碎屑密度流（PDC），在火山地区构成严重危害。2018年12月印度尼西亚Anak Krakatau火山爆发引发的侧翼坍塌引发的海啸清楚地证明了这一点，导致数百人死亡。尽管如此，这些现象仍然不为人所知，因为它们是不寻常和复杂的事件。此外，海啸监测系统通常被放置在地震风险高的地区，而不是沿着不稳定的海岸，因此，可能产生海啸的不稳定性在很大程度上是不可预测的，难以评估，往往制约不佳，斯特龙博利是世界上最活跃的火山之一，并已在过去几十年中进行了广泛的监测和研究。发生了许多海啸滑坡（空中和/或海底）;在过去的150年中至少发生了7次，在中世纪晚期，一次毁灭性的滑坡已经到达那不勒斯海岸200多公里。由于火山活动自那时以来一直保持类似，需要考虑更大规模的喷发、不稳定和海啸，而且由于其潜在的破坏性影响，有必要努力减轻这些灾难。特别是，2002年12月30日，滑坡引发的高达10米的海啸波对海岸造成了广泛的破坏，提高了人们对这一本来基本上被忽视的危险的认识。与2019年7月3日的喷发有关，该喷发造成了广泛的破坏和一人死亡，沿着Sciara del Fuoco斜坡（位于火山西侧的一个高度不稳定的侧翼）至少引发了三次质量流，两次陆上PDC和一次海底滑坡。同时，不同地点的三个浮标记录了海啸波的高度，即1.5米，Sciara del Fuoco附近0.5米，Ginostra村附近0.2米。本项目旨在收集有关这些物质流的数据，以准确评估引发海啸的过程。特别是，我们将收集样本，以根据岩土性质对动员材料进行鉴定，并将为边坡的陆上和水下部分建立详细的DTM。这将使我们能够将记录的波的大小与不稳定性的类型、流动体积和质量流的材料相关联。即使这里研究的海啸波比可能对生活在这一地区的人口构成威胁的海啸波要小，但如果本项目得到资助，它们所代表的事件可以构成一个自然实验室的例子，帮助我们更好地了解这些现象所涉及的过程。我们将利用这一经过充分研究和表征的事件进行精确的反分析，以表征海啸物质流的物质和行为，即了解沉积物和海啸波的最终和实际特征，我们能够确定它们是在何种条件下产生的。从这些结果开始，我们将能够对可能的不稳定情况进行大量的数值模拟。探索不同的潜在类型的质量流，将使我们能够确定其特性和海啸的规模之间的经验关系。评估这些经验法则是改进预警系统和减少与这些不可预测但极其危险的现象有关的风险的关键投入数据。

Tsunamis generated by large mass flows (described in this case then as tsunamigenic), like large landslides and pyroclastic density currents (PDCs), constitute a serious hazard in volcanic areas. This has been clearly demonstrated by the tsunami triggered by the Anak Krakatau eruption-induced flank collapse in December 2018 in Indonesia, which resulted in hundreds of fatalities. Nevertheless, these phenomena are still poorly understood as they are unusual and complex events. In addition, tsunami monitoring systems are typically placed in areas of high seismic risk rather than along unstable coasts, consequently instabilities that could produce tsunamis are largely unpredictable, difficult to assess and often poorly constrained.Stromboli is one of the most active volcanoes in the world, and has been extensively monitored and studied in the last few decades. Many tsunamigenic landslides (sub-aerial and/or submarine) have taken place; at least seven occurred in the last 150 years and during the late middle ages, a devastating one has reached the coast of Naples at more than 200 km distance. Because the activity of the volcano has remained similar ever since, larger eruptions, instabilities and tsunamis need to be considered and efforts to mitigate such catastrophes are necessary owing to their potential destructive impact. In particular, the 30 December 2002 a landslide-induced tsunami wave of up to 10 metres caused extensive damage to the coast and has increased awareness around this otherwise largely disregarded hazard. Associated with the 3rd July 2019 eruption, which caused extensive damage and one fatality, at least three mass flows were triggered along the Sciara del Fuoco slope (a highly unstable flank situated on the western side of the volcano), two subaerial PDCs and a submarine landslide. Simultaneously, three buoys in different locations registered the height of a tsunami wave, i.e. 1.5 m, 0.5 m close to the Sciara del Fuoco and 0.2 m near the village of Ginostra. The present project aims to collect data about these mass flows to accurately assess the process that triggered the tsunami. In particular, we will collect samples to characterise the mobilized material in terms of the geotechnical properties and we will build a detailed DTM of both the subaerial and submarine part of the slope. This will allow us to correlate the magnitude of the registered wave with the type of instability, the mobilized volume and the material of the mass flows. Even if the tsunami waves studied here are smaller than the one that could constitute a threat for the population living in this area, they represent an event that, if the present project is funded, could constitute a natural laboratory example that will help us to characterise and better understand the process involved in these phenomena.In addition, we will use this well studied and characterized event to run accurate back analysis to characterize the material and the behaviour of the tsunamigenic mass flow, i.e. knowing the final and actual characteristics of the deposits and of the tsunami wave, we are able to identify under which type of conditions they have been generated. Starting from these results, we will then be able to run a larger number of numerical simulations of possible instability scenarios. Exploring the different potential types of mass flows, will allow us to identify empirical relationships between their characteristics and the magnitude of the tsunami generated. Assessing these empirical laws constitutes crucial input data to improve the early warning system and to reduce the risk related to these unpredictable but extremely dangerous phenomena.