Today, Dec. 4, 2022, on Stromboli Island a tsunami warning was triggered by an intense pyroclastic flow impacting the sea surface. In photo a still image of the moment when the pyroclastic flow impacts the water.
The picture shows one of the two elastic beacons equipped with two pressure sensors that monitor the sea level at the two sides of the Sciara del Fuoco
Today, Dec. 4, 2022, the Stromboli Local Tsunami Warning System, designed and operated by the LGS of the University of Florence, triggered a tsunami warning on the island. Fortunately, the tsunami was small and caused no damage.
A tsunami can be large or small, like an earthquake, a landslide, or a volcanic eruption. Even a tsunami of a few centimeters, if generated by a sea disturbance induced by an earthquake, landslide or volcanic eruption, is still a tsunami. It is known, moreover, that even a tsunami with an amplitude of 50 centimeters can be very dangerous, because of its great energy and wavelength, which makes it look like a rushing torrent.
Data from the cameras and instruments that detected today's phenomenon show that the tsunami was generated by the impact on the sea surface of a rather intense pyroclastic flow, similar to that occurred in early October, but more intense.
Today the triggering threshold was exceeded, and the data was transmitted to the alert system of the Civil Protection Department, which immediately after the tsunami detection issued the alert, activating the sirens. In fact, pressure sensors located below the two elastic medes that served as sentinels at the Sciara del Fuoco detected a sea level anomaly of about 1.5 meters peak-to-peak (in the case of October 9, only +/- 5 cm had been recorded).
Specifically, the signal shows a first positive wave of about 50 cm and a subsequent lowering of about 1 meter. This is followed by other successive waves of comparable and then decreasing amplitude. The Ginostra tide gauge, belonging to ISPRA's National Mareographic Network, also detected a slightly lower anomaly.
Fortunately, no damages were caused by these waves in the coastal areas of the island of Stromboli nor in those of the other Aeolian islands.