Tsunamis in the Aeolian Islands (southern Italy): a review

Marine Geology 215 (2005) 11 – 21 www.elsevier.com/locate/margeo

Tsunamis in the Aeolian Islands (southern Italy): a review A. Maramaia,*, L. Graziania, S. Tintib a Istituto Nazionale di Geofisica e Vulcanologia di Roma—Italy Dipartimento di Fisica-Settore Geofisica-Universita` di Bologna—Italy

b

Received 20 October 2003; received in revised form 1 March 2004; accepted 8 November 2004

Abstract The Aeolian Islands, located in the south Tyrrhenian Sea to the west of Calabria and to the north of Sicily, constitute the Aeolian Volcanic Arc, characterized by a relevant volcanic activity with an established tsunamigenic potential. According to the documentary sources that are available for the Aeolian tsunamis, and that cover unfortunately only about the last 100 years, Stromboli is responsible for the majority of the events. Some cases are also known to have occurred at the islands of Salina and Vulcano. In terms of intensities, the most destructive events are those originated by the Stromboli volcano, reported to have produced severe destruction to boats and houses, and to have even caused injuries and fatalities. In this work, we focus on the historical events, and discard the paleotsunami occurrences that were probably associated with the ascertained flank collapses of the volcanic cones. We also neglect the recent destructive tsunamis of 30 December 2002, which were caused by a series of mass failures at the Sciara del Fuoco, since observations and analyses are of such an amount that deserve to be illustrated in devoted papers. The bulk of the present research consisted in collecting all the available data on the historical cases (the first in order of time is the July 1916 Stromboli tsunami) with the purpose of casting more light on their generation mechanism and on their effects, and consequently of contributing to the studies on assessment of tsunami hazard and risk in the Aeolian Islands and in the southern Tyrrhenian sea. D 2004 Published by Elsevier B.V. Keywords: Aeolian Islands; historical data; tsunami; volcanic activity

1. Introduction The Aeolian archipelago, located in the southern Tyrrhenian Sea, north of Sicily, is made up of 10 islands and islets, only 7 of which are populated, for a

* Corresponding author. Fax: +39 65041303. E-mail address: [email protected] (A. Maramai). 0025-3227/$ - see front matter D 2004 Published by Elsevier B.V. doi:10.1016/j.margeo.2004.03.018

total of 12,000 inhabitants (see Fig. 1). The archipelago has a volcanic origin and all the islands were submarine volcanoes that emerged about 700 ky ago. Aeolian Islands are part of a marginal bfore-arc deepbasinQ system originated by the collision between African and Eurasian plates. They are characterized by a recent volcanism, started during Pleistocene, for which two main periods of activity can be distinguished. During the first period, the volcanic edifice

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Fig. 1. Map of the populated islands of the Aeolian group.

of Panarea, the oldest in the archipelago, rose and the islands of Filicudi, Alicudi, and part of Salina and Lipari were formed. After a period of stoppage, in the upper Pleistocene, a second phase started, with the completion of Lipari and Salina islands and with the creation of Vulcano and Stromboli islands, the most active apparatus in the area. Aeolian Islands are one of the Italian areas most active and interesting from the geophysical point of view, being characterized, at present and in historical times, by a relevant volcanic activity with significant eruptions and/or explosions often associated with earthquakes, landslides and tsunamis. As regards tsunamis, the first historical reports concern an event originated in Stromboli in 1916. It can be asserted that the history of the tsunami events is very likely complete since the end of the XIX century, when the Aeolian volcanoes attracted the systematic scientific interest of volcanologists (see Mercalli, 1881). Since 1916 up to now, the Aeolian archipelago has experienced eight events, including and counting as one the destructive tsunami that occurred on 30 December 2002 and that, according to the most recent analyses, can be seen as a double event originated by

two distinct mass failures taking place with a 7-min separation. The most intense of these events occurred in Stromboli, one took place at the island of Salina in association with a local earthquake and one was generated in Vulcano island as a consequence of a subaerial landslide detached from the volcano flank. The purpose of this paper is to provide a comprehensive exposition of all the available reports on the historical tsunamis affecting the Aeolian Islands, with the exception of the last 30 December 2002 occurrences, the analysis of which is left to other papers. To accomplish this goal, we gathered the material from specific monographs and scientific articles, from articles available in contemporary chronicles and in local and national newspapers, and when possible, we interviewed persons that happened to be direct eyewitnesses of the events or could refer accounts transmitted through oral tradition by elder people. In the following sections, first this paper characterises briefly the main features of the volcanic activity of Stromboli and Vulcano, where all Aeolian tsunamis of volcanic origin were originated, and then, following a chronological order, it provides an analysis of all the tsunamis that are known to have occurred in this region.

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2. The most active volcanoes: Stromboli and Vulcano 2.1. Stromboli Stromboli is located in the northeastern part of the Aeolian arc and is the main volcanic centre of a large composite volcano. A map of the island is depicted in Fig. 2. The edifice, characterized by steep slopes, reaches the elevation of 924 m a.s.l., while the submarine base is located approximately at a depth of 2000 m. The volcano was affected by several collapses in geologic times involving the SE flank in a first stage and then later at the NW sector, where the series of the most recent recognisable collapses took place. The last one can be probably dated less than 5000 years ago and originated the Sciara del Fuoco (Pasquare` et al., 1993; Tibaldi, 2001), and is speculated to have been the source of a huge South-Tyrrhenian-wide tsunami (Tinti et al., 2000). Stromboli is characterized by a persistent activity, which was known also to the ancient populations, who called it bthe lighthouse of the MediterraneanQ. Even Homer mentions an eruption of this volcano, and

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Strabo, Plinius, Pausanias, and other Greek and Roman writers describe the explosions of Stromboli as very usual events. The activity of the volcano consists of rhythmic mild gas explosions that follow one another at intervals of 10–20 min with ejection of ashes, incandescent crystal-rich scoriae, and blocks. This normal activity, known as bStrombolian activityQ, is interrupted from time to time by more energetic explosions, named bmajor explosionsQ and bparoxysmsQ. A major explosion is characterised by the throw of lava bombs and blocks at distances of several hundred meters and by the ejection of lapilli and ash as far as some kilometres. A bparoxysmQ is an even more energetic eruption, usually lasting for several hours to a few days, during which showers of incandescent scoriae are produced, and bombs are ejected over distances of several kilometres. These powerful eruptive manifestations usually take place at intervals of years or decades (Barberi et al., 1993; Rosi et al., 2000). Although the inhabited areas in the island are situated in the safest parts, they remain under the threat of paroxysms; and fallout of bombs and blocks, tephra accumulation, formation of hot avalanches, and tsuna-

Fig. 2. Map of Stromboli island. The localities mentioned in the text of the paper are reported.

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mis are often reported to have caused damage and, in some cases, fatalities. In the last century, the strongest paroxysmal events occurred in 1919 and in 1930. 2.2. Vulcano Vulcano is the southernmost island of the Aeolian archipelago. Four main volcanic structures may be identified on the island: the bCaldera del PianoQ, which represents the area of the primordial Vulcano, the bLentia calderaQ, that encircles the smaller caldera

called bLa FossaQ, and the bVulcanelloQ peninsula that is the youngest cone one finds in the island (see Fig. 3). About 10,000F1000 years ago, the present volcanic cone, equally named La Fossa, started to form inside the inner caldera. The volcanic edifice reaches 391 m a.s.l. with a crater diameter of about 600 m. Most of the eruptions that occurred in historical times are from the volcano La Fossa where one can recognise a series of craters that moved progressively westwards (Frazzetta et al., 1983; Frazzetta and La Volpe, 1991). All craters are

Fig. 3. Map of Vulcano island.

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associated with eruptive cycles that started with explosions, ended with lava flows, and were separated by very long quiescent periods. The last known big explosive period started in August 1888 and lasted until March 1890. During this eruption, a big amount of old vent material and fresh lava was ejected and typical projectiles were launched, that were called bbread-crustQ bombs. This eruption was used as paradigmatic to distinguish to the bvulcanian-style activityQ, an expression used by volcanologists to typify moderate- to high-energy eruptions usually beginning with steam-driven explosions and continuing with the explosive ejection of solid or of very viscous fragments of new lava and blocks, and with almost no lava outflow. Since that time, Vulcano had various episodes of unrest, the major of which took place in 1987–1988, was characterised by an increased level of volcanic and seismic activity (Falsaperla et al., 1989; Barberi et al., 1991), and was responsible for a local tsunami.

3. The historical tsunamis In this section, a detailed description of the Aeolian tsunamis is provided in order of occurrence. It results from a scrupulous and careful search and scrutiny of the sources: original documents and reports as well as newspaper articles were examined, and advantage has been also taken from the reliable historical compilations, such as the catalogue of the Italian and European tsunamis (see Tinti and Maramai, 1996; Maramai et al., 2003), etc. In addition, a campaign of interviews were conducted to the elderly inhabitants of the islands who happened to be direct observers of the events or were in close relationship with direct witnesses. 3.1. July 3, 1916 Stromboli On January 5, 1916, the normal activity of Stromboli was broken by an intense explosion with the generation of an enormous cloud loaded with ash. The explosions with ash emissions and projection of incandescent material increased until June. On the Sciara del Fuoco, the lava started to flow down for a short stretch. On the 3rd of July at 23:21 (GMT), anticipated by some premonitory phenomena, a violent explosion occurred that was accompanied by

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an earthquake (Mm=5, I max=7 MCS), causing light damage to the buildings. The shock was felt quite strong in Lipari, Salina, Panarea, and Vulcano islands, and along the Tyrrhenian Calabrian coasts, from Amantea to Capo Vaticano. The NE side of the Stromboli island was covered by tephra reaching the beach and the roofs of the houses from Piscita` to San Vincenzo. The hot material ejected on the cultivated fields produced some fire. Ponte (1921), describing phenomena that accompanied the explosion, reports: . . .The inhabitants of Piscita`, soon after the explosion, observed a sudden sea retreat, and then violently the water invaded almost completely the beach. The first wave penetrated for about 20 m on the beach and heaps of seaweeds were carried on land. This sea behaviour, as the inhabitants tell, was only noted on the northern beach of the island (Spiaggia Lunga), while at San Vincenzo, on the north-eastern coast, the sea water behaviour was as usual. Cavasino (1935) reports that the sea level rose about 10 m at San Bartolo village. Similar descriptions are reported on July 4 and 5 in the following newspapers: Il Corriere di Napoli, La Gazzetta del Popolo and La Tribuna. 3.2. May 22, 1919 Stromboli In February 1919, it started a period of extraordinary activity of the Stromboli volcano, reaching its maximum on May 22, at about 17:45 (local time), with a very violent explosion. Up to 1-ton heavy blocks of lava fell on the village of Stromboli destroying 10 buildings and damaging many others severely. At Ginostra, two houses collapsed, and some fire was reported to occur in the neighbouring fields. Three people died and twenty were injured because of the blocks fall (Platania, 1922; Oddone, 1923). As regards the tsunami, Platania (1922) quotes an account of an eyewitness who was at the observatory of Punta Labronzo: b. . . the violent eruption, with impressive rumbling and enormous ash emission, was accompanied by a sea retreat by about 200 m . . . shortly after the explosion the sea water flooded the beach all around for about two minutes, carrying all the boats in the neighbouring vineyards by more than 300 m . . .Q. We have been able to find some further relevant accounts in the newspapers. Soon in the following day edition (May 23rd), bLa NazioneQ gave the report here below: b. . .Violent explosion of Stromboli, lava

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blocks were launched causing the collapse of some houses. Three victims ascertained and many injured people. . .Q. A few minutes after the beginning of the eruption a huge water wave was produced b. . .for a while it looked as if the other Aeolian Islands had disappeared. The tsunami lasted more than ten minutes. . .Q. One day later, on May 24, the newspaper called bL’Osservatore RomanoQ added some further details on the tsunami effects: b. . .The initial explosions were followed by a tsunami causing damage to many fishing boats that were thrown on the beach at a distance larger than 150 m. . .Q. We found the same descriptions of the local impact replicated in other newspapers, namely bIl MessaggeroQ, bIl Corriere della SeraQ, bIl Mattino,Q and bIl Giornale di SiciliaQ. Information about the anomalous sea behaviour associated with the propagation of the tsunami can be also found for some localities outside the Aeolian archipelago. At Ustica, an island about 150 km west of Stromboli, an anomalous light sea movement was observed. In Capri at Marina Piccola, more than 200

km north of Stromboli, some sailors noted a sea retreat leaving some dried rocks that were more than 1 m under the normal sea level. After 67 s, some big waves flooded the beach exceeding the usual limit (Platania, 1922). Quite a large number of tide-gauge records were available: Cagliari in Sardinia, Catania, Palermo, Messina, and Faro (Messina) in Sicily, Naples, and Civitavecchia on the Tyrrhenian coast of the Italian peninsula. Among all of them, the tsunami signal is only detectable on the two tide-gauges located in Faro and in Messina. The Faro record is quite smooth, probably as the effect of a strong instrumental highcut filtering (see Fig. 4a, where the graph is plotted with reverse time axis). In the record, the tsunami signal can be distinguished to start at approximately 18:00 (see arrow in Fig. 4a). It is really very small (amplitude less than 1 cm) and lasts approximately for 90 min. In the Messina mareogram, plotted in Fig. 4b, a clear group of small amplitude (~5 cm) oscillations can be seen that start at about 18:00 with period of 11

Fig. 4. (a) Tide-gauge record at Faro during the May 22, 1919 tsunami (modified after Platania, 1922). (b) Tide-gauge record at Messina during the May 22, 1919 tsunami (modified after Platania, 1922).

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min. The main perturbation lasts for about 80 min and is followed by a long coda during several hours (Platania, 1922). It is worthwhile to stress that, nowadays, the memory of this event is still strong among the few elder inhabitants. 3.3. August 17, 1926 Salina This is the only tsunami that reportedly occurred in Salina island and it was originated by an earthquake probably of volcanic origin. On August 17, at 01:43 (GMT time), a strong earthquake (I max=VII–VIII MCS) occurred in the Aeolian Islands, with epicentre located near Salina. At Malfa and Pollara, two localities of Salina (see Fig. 5), most of the houses were heavily damaged. Two injured people were reported in Malfa due to the collapse of buildings. Many landslides were observed in the whole island. At Filicudi and Lipari islands, only slight damage was reported. The shock was felt on the coasts of Sicily and Calabria. On the beaches of Malfa and Capo Faro, in Salina island, a light tsunami was observed with an initial withdrawal of the sea (Cavasino, 1935). Newspapers reported detailed information on the earthquake, but gave no mention of anomalous sea behaviour.

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3.4. September 11, 1930 Stromboli This is one the most impressive events occurred at Stromboli in the last 200 years: the eyewitnesses’ accounts are still rich in pathos and details. On September 11, at 10:00, a first tremendous explosion threw a large amount of volcanic material and lava bombs particularly on the western and southwestern side of the island. Hot avalanches and two secondary lava flows were originated. One of them stopped very close to the church of San Bartolo and the other entered the sea at Piscita`. At Ginostra, most roofs were destroyed. A second explosion, shortly after the first one, produced a dense rain of ash and tephra. Lava blocks hit the north-western and north-eastern side of the island, killing four persons and injuring several people at the villages of San Vincenzo and San Bartolo, where moreover many fires burnt the surrounding fields. The paroxysm lasted for about 20 min. A tsunami followed the explosion and was responsible of two more fatalities. Eyewitnesses reported that just before the end of the paroxysm the sea at Sopra Lena retreated by about 100 m and then flooded the beach by 200 m in 3 min. At Piscita`, in the Eolo’s grotto, a fisherman, who was trying to take shelter from

Fig. 5. Map of Salina island.

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the rain of burning lava, ran towards the sea and a wave, boiling hot due to the heat of the lava that had come in contact with the sea water, attacked him causing mortal scolds (Abruzzese, 1936). The second victim was drowned by the wave at San Vincenzo. A large number of newspapers gave report of the tsunami giving special emphasis to the fatalities that it caused. On September 13, bIl Corriere della SeraQ, bIl Giornale di SiciliaQ, bIl Mattino,Q and bIl Giornale d’ItaliaQ reported: b. . .On San Vincenzo beach the body of the fisherman Giuseppe Tripi was found. He was carried away and drowned by the huge and violent tsunami waves caused after the eruption. . .Q. In the same date, bLa NazioneQ wrote: b. . . At the time of the crater opening a tsunami occurred. According to some witnesses the sea water rose more than 2.5 m moving forward towards the beach dragging and killing an old man that was on the beachQ. Imbo` (1930) reports a run-up of about 2.5 m. At Capo Vaticano, on the Calabrian coast, a sea wave of 2–3 m was observed. It is worth pointing out that this tsunami is the only one known to have caused fatalities among the events of the Aeolian Islands. 3.5. August, 20 1944 Stromboli After a period of intense activity, on August 20 at 07:30, a terrible explosion occurred with lava bombs and ash ejected up to great heights. A stream of lava entered the sea at Sciara del Fuoco, and concomitantly water waves were observed that nearly caused the shipwreck of a boat. A hot avalanche at the Forgia Vecchia, on the opposite side of the island, reached the coast where big waves were noted. Eyewitnesses reported that the beach was full of fish (Ponte, 1948). Some old inhabitants of the island remember the eruption of that year and a light tsunami seen shortly after the explosion, that destroyed one house (Barberi et al., 1993). No news, either about the eruption or about the tsunami, was found in contemporary newspapers, which is not strange, since in that world-war period, their attention was attracted by much more dramatic events. 3.6. February, 1954 Stromboli A strong explosive eruption occurred at Stromboli volcano at the upper end of the conduit, with lava

effusion from February 1, 1954 to March 13, 1954 (Cucuzza Silvestri, 1955). Interviews to eyewitnesses revealed the occurrence of a tsunami associated with the explosion: between Forgia Vecchia and Punta dell’Omo, a first sea withdrawal of about 10 m was observed, leaving some boats stranded; then two or three waves (the second bigger than the others) invaded the beach carrying some boats in land. At Scari, the salt warehouse was damaged by the wave. Contemporary newspapers give no information on the tsunami. 3.7. April, 20 1988 Vulcano On April 20, 1988 a landslide of approximately 200,000 cm3 occurred on NE flank of volcano La Fossa in the island of Vulcano during a period of increased volcanic activity starting in June 1987, with measured ground deformations and geochemical anomalies, and with accompanying seismic activity that culminated in the seismic swarm of August 9–14 1988. The direct cause of the slide is difficult to identify: the simplest hypothesis is that the mass was pushed to a critical stability point by seismic vibrations associated with the earthquake sequence affecting the region surrounding Vulcano from March to June 1988. However, some other causes can be invoked, such as hot fluid circulation in the hydrothermal system (Rasa` and Villari, 1991). The landslide entered the sea, thus generating a tsunami. Instrumental data do not exist since no tidegauges were present in the area, but many people observed it. A fisherman, who at the time of the landslide was in his boat just inside the generation area, reports that, at about 05:30 local time, he heard a big noise and, looking at the coast, he had the impression that the mountain was running towards him. A positive wave was excited that raised the boat without damaging it. The water wave was approximately 1–2 m high. Then, he felt the boat go down, and other smaller oscillations followed the first wave. Another boat in the same bay, but further away from the source, was impacted by the tsunami with no damage. In the nearby harbour of Porto di Levante (see Fig. 3), many people observed sudden waves entering the harbour, similar to those produced in the sea by a storm, but the weather was fine with no wind. Wave amplitude was estimated to be approximately 0.5 m (Tinti et al., 1999).

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Despite the very recent occurrence of this event, it had no mention in newspapers, probably because it was a very local and light tsunami not associated with any earthquake or volcanic explosion.

4. Conclusions The research has confirmed that, with the exception of the 1930 Stromboli event, the descriptions concerning the Aeolian tsunamis are scarce and very fragmen-

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tary. A precious integration comes from memories of elder inhabitants that, however, are sometimes faded or imprecise. A detailed reconstruction of facts is therefore difficult, also because the studied area was sparsely inhabited. In spite of all of this, some important conclusions can be attempted as regards the mechanism of tsunami generation and the tsunami impact. A schematic summary of the information on all the tsunamis treated in this study is given in Table 1. The first consideration is that all the major volcanic crises that occurred in Stromboli (6) and in Vulcano (1),

Table 1 Summary of the Aeolian tsunamis with main tsunami parameters (time, source area, coordinates, cause, tsunami intensity, and description) Year

Month Day Source-area Latitude/Longitude Causea

1916 7

3

Stromboli

38:48/15:12

1919 5

22

Stromboli

38:48/15:12

1926 8

17

Salina

38:50/14:45

1930 9

11

Stromboli

38:48/15:12

1944 8

20

Stromboli

38:48/15:12

1954 2

2

Stromboli

38:48/15:12

1988 4

20

Vulcano

38:24/14:58

a

Speculated submarine landslide in the Sciara del Fuoco Speculated submarine landslide in the Sciara del Fuoco Speculated submarine landslide associated with an earthquake Double event: one caused by an observed hot avalanche at Piscita` and one by a speculated submarine landslide

Tsu Intb Short description 2

Sea retreat and flooding of the beach called Spiaggia Longa in northern Stromboli

3

In Stromboli, sea retreat by 200 m and flooding of the beach. Boats carried inland in the vineyards by more than 300 m. Initial sea retreat at Salina

2

2c 4d

Double event: one caused 2e 4f by a speculated mass f ailure concomitant with an observed lava flow at Sciara del Fuoco, and one caused by an observed hot avalanche at Forgia Vecchia Speculated submarine 3 landslide in SE coast Observed subaerial 2 landslide in NE flank of La Fossa

A hot avalanche raised water waves that scalded and killed one man in the Eolo’s grotto (northern Stromboli). Landslideinduced tsunami: sea retreat by 100 m followed by flooding of the beach of Sopra Lena by 200 m (NE Stromboli). One man killed in the beach of San V incenzo (NE Stromboli) by 2.5-m-high waves. On the Calabrian coast, wave of 2–3 m observed. Big waves in the Sciara del Fuoco area. Big waves in the East coast of Stromboli. One house destroyed. Beach full of fish.

Initial sea retreat followed by water waves in E Stromboli. Boats carried inland. Water wave 1–2 m high in the source area. Wave with 0.5-m amplitude in Vulcano harbour.

All tsunamis of Stromboli occurred during periods of major eruptions. The 1988 tsunami of Vulcano occurred during a period of increased seismic and volcanic activity. b Tsunami intensity in the Ambraseys–Sieberg scale. c Intensity of the tsunami due to the hot avalanche at Piscita`. d Intensity of the tsunami observed in Sopra Lena and in San Vincenzo. e Intensity of the tsunami observed in the Sciara del Fuoco. f Intensity of the tsunami observed in Forgia Vecchia.

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that are the only active volcanoes of the area, resulted in a tsunami, which means that the tsunamigenic potential of this region is considerable. The second remark concerns the mechanism of water waves production. On this issue, the sources are quite evanescent, and only in a few cases either an explicit mention to the cause is made, or an explicit speculation is attempted, as is listed here below: (1)

(2) (3)

(4)

Dense and fast pyroclastic flows are responsible for the waves that killed a fisherman in the course of the 1930 Stromboli crisis; A hot avalanche is the cause of the tsunami hitting the western coast of Stromboli in 1944; A subaerial landslide, the size of which could be quantified through pre- and post-failure aerial photograph sets, produced the 1988 Vulcano tsunami (Achilli et al., 1998); The collapse of the eruptive column was invoked by Ponte (1921) to explain the Stromboli tsunami of 1919.

In spite of the scarcity of the informative material, however, some sensible conjectures can be advanced at least on the tsunami generation in Stromboli, taking advantage of what we know of the last occurrences of the 30 December 2002. Similarities among the reports of the historical tsunamis and of the last cases are quite strong, suggesting consequent similarities in the source mechanism. More explicitly, it can be stated that: (1)

The accounts on the 1916 are compatible with the hypothesis of a submarine landslide occurrence in the Sciara del Fuoco, causing the sea to retreat first and provoking larger damage on the northern Stromboli coast. (2) The 1919 tsunami was probably due to a second, and possibly larger, submarine failure in the same area, although the aforementioned Ponte’s supposition of the eruptive column collapse cannot be ruled out and deserves attention and analysis, for example, through proper modeling. (3) The 1930 Stromboli tsunami was likely a double event, one caused by the hot avalanche down to the northern flank of the volcano affecting Piscita`, and one, stronger, due to a submarine failure of the Sciara del Fuoco.

(4)

(5)

The 1944 tsunami is compatible with the hot avalanche observed at Forgia Vecchia on the southwestern flank of Stromboli. The 1954 tsunami could be explained by a submarine failure taking place in the southeastern flank of Stromboli.

According to the point of view expressed here, all the tsunamis that occurred in the Aeolian Islands, including also the 2002 events, were caused by mass movements (either hot avalanches or landslides), with the exception of the earthquake-induced 1926 Salina tsunami. However, since the earthquake size is probably too low to generate an observable tsunami through the dislocation of the sea floor, even for this case, some undetected submarine mass movement could be reasonably invoked. As regards the effects, all historical tsunamis were local since they are reported to have produced damage at most in the same island where they were originated. It has to be remarked, however, that in the past, the coastal areas prone to inundation were not exploited by human activity at the same level as they are today and therefore the effects of the tsunamis could not be so catastrophic. In the last decades, the islands underwent a great tourist development and the tsunami impact today is potentially by far greater than it was in the past, as it has been confirmed by the December 2002 Stromboli tsunamis. The last observation concerns the instrumental data. It is a lucky circumstance that the 1919 tsunami could be detected at least by two far-field tide-gauges located in Faro and in Messina, and that at the time of tsunami occurrence, other tide-gauges were in operation and continuously recording sea-level oscillations. Conversely and unfortunately, no near-field or far-field mareograms are available for the last 2002 tsunamis, with the possible exception of records taken in the Gulf of Naples by the Osservatorio Vesuviano (INGV) local tide-gauge network. In addition, this is a hint of how much the tsunami hazard was overlooked for the Aeolian archipelago and more generally for the southern Tyrrhenian Sea. This historical review is a contribution to put the right and due light on the tsunami hazards in the region, and has emphasised the extremely important role of mass instability in tsunami generation, which opens the question of the

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detection, mapping and monitoring of the unstable subaerial, and especially underwater, bodies in the correspondence of the Aeolian Islands volcanic edifices.

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