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

Lead Research Organisation: University of Plymouth
Department Name: Sch of Geog Earth & Environ Sciences

Abstract

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.

Planned Impact

The Aeolian Islands host a population of more than 15000 permanent residents; this reaches peaks of hundreds of thousands during the high touristic season. Tourism is also the main source of income for the population living in Stromboli where visitors are mainly attracted by the opportunity to see an active volcano from close by. While in general the population is used and prepared to low or moderate explosive activity, little is known about the landslide induced tsunamis and the related risks. In 2002 after a tsunami of this type caused extensive damage, efforts have been made by the scientific community to increase our understanding of these phenomena. Since then early warning systems have been put in place. Larger and more devastating events though have been recorded in the past during the late middle ages and their extent reached the coast of Naples (around 250 km away). Because the activity of the volcano has remained similar ever since, larger eruptions and potential tsunami need to be considered. Therefore, efforts to mitigate such catastrophes are necessary owing to the potential impact on the population in Stromboli, on the surrounding coastal area and to the economy of the Aeolian Island region. The early warning system currently in place at Stromboli is mainly based on the recording of tsunami wave height registered by buoys. Assessing the volumes and type of mass flows that could induce significant tsunami waves will enable us to improve this system. In fact, with a continuous monitoring of the slope, the empirical model derived from this project could contribute in assessing when the probability of the failure of significant volumes (subaerial and submarine) becomes high enough to trigger an early warning. The Italian partners of this project are amongst the main responsible of the monitoring of the activity at Stromboli and they are affiliated to the Department of the Italian Civil Protection. For these reasons, the findings of this project will be directly used for the risk management of the island and will have a direct impact on the monitoring and early warning system. After the necessary modifications and adaptations, the empirical model could be used as starting point in other similar contexts. In addition, as affiliated to the UNESCO Chair on "Prevention and Sustainable Management of Geo-Hydrological Hazard", the University of Florence project partner will disseminate the progress and the results of the present research (see letter of support). This will have a global impact, as it will ultimately help increasing awareness and understanding of these lethal but still poorly constrained phenomena.

Publications

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Manzella IM (2021) EGU General Assembly 2021

 
Description Through close collaboration with our partners in France and Italy, we were able to produce some realistic and informative simulations that enabled students in the UK and in Italy to become more aware of the problem of tsunamis caused by landslides and pyroclastic density currents during an explosive eruption. This is often an unknown hazard to the public, especially for people who visit Stromboli or other volcanic Islands as tourists. For this reason, increasing awareness and educating the young generation, who are likely to visit those places in a globalized world, is extremely important to decrease risks.
Exploitation Route Including an explanation of this hazard in educational actions and tools is needed to reach a wider public. In particular, understanding what to do and how to act when an eruption occurs and there is the likelihood of a tsunami generation is key to increase resilience. 3D visualization to better visualize the effects of this and the reach of a tsunami generated by a PDCs or landslides should be included in digital and physical exposition and shown to the local population and authorities. We are working with Dr Federico Di Traglia to see how we can implement those actions in further projects with the Civil Protection
Sectors Communities and Social Services/Policy,Education,Environment,Leisure Activities, including Sports, Recreation and Tourism

 
Description The workshop I have held about the numerical modelling of tsunamigenic flows for the Girls Into Geoscience has allowed several attendees (girls between 12 and 18 years old) to better understand this phenomenon. All the comments about the workshop were great and when asked what they have learned from the whole event many among them have answered that they have learnt about tsunamigenic flows and it has increased their awareness about this phenomenon.
First Year Of Impact 2020
Sector Education
Impact Types Cultural

 
Title New accurate bathymetry 
Description Thanks to the present project we were able to collect a new accurate bathymetry of the area close to the Sciara del Fuoco. This data though they are submitted to embargo from the University of Sapienza Rome. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? No  
Impact This new bathymetry will allow us to better assess the propagation of the tsunami waves. It was also used to assess the sensitivity of the model used to changes in the bathymetry data. 
 
Title VolcFlow sensitivity analysis 
Description Around a hundred simulations have been carried within the present project to test the sensitivity of VOlcFlow and the sunami waves generates by the model to assess influence of parameters such as the accuracy of the DEM and the rheology used and the Matlab version used and the conditions at the border. With our simulations issues with the border, conditions could be identified where the waves produce a back wave when it hits the corner of the field view. this should not happen and we were able to identify this problem and now Karim Kelfoun is working to rectify this. 
Type Of Material Computer model/algorithm 
Year Produced 2020 
Provided To Others? No  
Impact We identified a bug in the model and now the developer of the code is working to correct this. This is having a great impact to improve the use of VolcFlow to assess tsunamis hazard caused by mass flows at Stromboli but also everywhere else this problem is present. I have put as link the simulations we have produced for the GIrl into the Geosciences workshop to show the correction of the returning waves problem 
URL https://www.youtube.com/watch?v=NuFCWBo4cPY
 
Description EGU/IAVCEI/COV sessions 
Organisation National Institute for Geophysics and Volcanology (INGV)
Country Italy 
Sector Public 
PI Contribution Thanks to the present project I have established a close collaboration with Dr Federico Di Traglia and Dr Rosanna Bonasia, Dr Alessandro Bonforte, Dr Felix Gross. We have designed 3 sessions in 3 different international conferences on instabilities in volcanic settings. I have contributed in the design of the sessions and in the advertisement among my networks.
Collaborator Contribution Partners of the project have contributed to the session design and also with abstract submission
Impact Sessions accepted in the 3 different conferences
Start Year 2019
 
Description EGU/IAVCEI/COV sessions 
Organisation National Polytechnic Institute
Country Mexico 
Sector Academic/University 
PI Contribution Thanks to the present project I have established a close collaboration with Dr Federico Di Traglia and Dr Rosanna Bonasia, Dr Alessandro Bonforte, Dr Felix Gross. We have designed 3 sessions in 3 different international conferences on instabilities in volcanic settings. I have contributed in the design of the sessions and in the advertisement among my networks.
Collaborator Contribution Partners of the project have contributed to the session design and also with abstract submission
Impact Sessions accepted in the 3 different conferences
Start Year 2019
 
Description EGU/IAVCEI/COV sessions 
Organisation University of Kiel
Country Germany 
Sector Academic/University 
PI Contribution Thanks to the present project I have established a close collaboration with Dr Federico Di Traglia and Dr Rosanna Bonasia, Dr Alessandro Bonforte, Dr Felix Gross. We have designed 3 sessions in 3 different international conferences on instabilities in volcanic settings. I have contributed in the design of the sessions and in the advertisement among my networks.
Collaborator Contribution Partners of the project have contributed to the session design and also with abstract submission
Impact Sessions accepted in the 3 different conferences
Start Year 2019
 
Description Invited Online Lecture, 02/12/2020, University of Cagliari, Esplosioni, collassi di versante e tsunami a Stromboli: come capirli, prevederli e prepararci 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact Inivted to give a lecture/Workshop on my work on Stromboli. Students and academics from all over the world have attended as well as collaborator of the project
Year(s) Of Engagement Activity 2020
URL https://corsi.unica.it/scienzeetecnologiegeologiche/2020/11/29/avviso-di-seminario-mercoledi-2-dicem...
 
Description Press release about the project 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact University Press release about the project
Year(s) Of Engagement Activity 2020
URL https://www.plymouth.ac.uk/news/research-expedition-aims-to-reveal-hidden-secrets-of-volcanic-tsunam...
 
Description Workshop for the award winning event Girls into Geoscience Volcanoes, landslides, tsunamis - why look at one? Let's do them all! 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact More than 80 students and their teachers attended this online workshop organised for the GIG
Year(s) Of Engagement Activity 2020
URL https://www.plymouth.ac.uk/whats-on/girls-into-geoscience