April 20, 1988 Tsunami: La Fossa Volcano, Vulcano Is., Italy

A mass of about 200,000 cubic meters of material from the northeast flank of the volcano La Fossa on the Island of Volcano in the southern Tyrrhenian Sea became detached. It fell down into the sea in about 10 seconds, generating a small tsunami in the bay between Point Nere and Point Luccia. This part of the island is completely uninhabited. A fisherman in a nearby boat observed the event. The positive leading wave came from Point Rioa and propagated throughout the bay. A second fisherman, who was near Point Luccia, also noticed the wave.

A wave of about 5.5 meters height was seen in the Porto di Levante and presumably even at Monterosa, Lipari Island. The seismometer network of the Aeolian Islands recorded the landslide vibrations. The landslide mass was estimated through models of the terrain inferred from photogrammetric campaigns carried out in 1981 and 1991. (reference #1315)

On April 20 1988 a landslide of approximately 200,000 cubic meter occurred on NE flank of volcano La Fossa on the island of Vulcano. The volcanic activity of the cone of La Fossa increased in 1987-1988 starting in June 1987, with measured ground deformations and with a seismic swarm on 9-14 August 1988. The direct cause of the slide is difficult to ascertain: 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. Some other causes can be invoked, such as hot fluid circulation in the hydrothermal system (Tinti r533). The landslide entered the sea generating a tsunami. Instrumental data do not exist since no tide gauges were present in the area, but the tsunami was clearly observed especially in the harbour of Porto di Levante. Observational data are from eyewitnesses (Tinti r533). A fisherman, who at the time of the landslide, was in his boat just inside the generation area, reports that at about 5:30 am 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 fist wave. Another boat in the same bay but further from the source, was impacted by the tsunami with no damage. In the harbour of Porto di Levante 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. Information (not from eyewitnesses) about observed waves as 0.5m amplitude in some places on Lipari island are reported. Tsunami intensity 2. (reference #4139)

1988 04 20, Aeolian islands, Italy: A c.200,OOO m3 landslide occurred on La Fossa, Vulcano island, entered the sea and generated a tsunami 1-2 m high clearly observed in the harbour Porto di Levante. The first wave was positive, then other sea oscillations followed. (reference #10357)

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). (reference #3078)