The 30 December 2002 landslide-induced tsunamis in Stromboli: sequence of the events reconstructed from the eyewitness accounts

Abstract

Abstract. On 30 December 2002 the coast of the volcanic island of Stromboli, in the Tyrrhenian sea, Italy, was attacked by two tsunamis generated by landslides that took place on the north-west flank of the volcano. The landslides and the tsunamis represented the most impressive and threatening episodes of a strong effusive eruption, started on 28 December from a new vent which opened close to the north-east crater of the volcano. In spite of the intensified monitoring carried out in response to the eruption, the landslides and the ensuing tsunamis were not foreseen, and the available instrumental data are insufficient to allow a precise reconstruction of the sequence of the events. The seismic network recorded two main landslides along the steep slope of Sciara del Fuoco, with onset around 13:15 and 13:23 local time (GMT+1). The tsunamis were the direct consequence of the mass movements. Three main post-event surveys helped make assessment on the wave impact on the coast.In this paper the attention is focussed on the accounts of the eye-witnesses, that help us clarify and understand what happened. People in the source area (Sciara del Fuoco) reported a small-volume subaerial slide taking place first, then a sharp cut forming in the sea water down to the sea floor (about 10-20 m deep) and propagating almost parallel to the coastline, be concomitantly associated with a sea retreat and a subsequent sea advance. It is suggested here that the cut was the effect of a large submarine landslide that detached from very close to the coast and produced the 13:15 signal in the recorded seismograms. The second, mostly subaerial, slump was observed to slide down 7-8 min later and to excite a train of waves some distance offshore. Not all the witnesses realised that two distinct tsunamis occurred. The tsunami period was probably in the order of 100 s, but shorter period crests were seen to travel on the top of the long-period waves by several persons. The duration of each tsunami was appreciated to be around 5-7 min. It is difficult to ascertainCorrespondence to: S. Tinti (steve@ibogfs.df.unibo.it) which tsunami was the largest, since there is no full agreement among the observers, but certainly by accounts both were characterised by large destructive waves.

The hydrodynamics of landslide tsunamis: current analytical models and future research directions

“…3 d). This dynamics is consistent with the eyewitness accounts of the 2002 Stromboli tsunami, for which Tinti et al (2005) report: "the water withdrew, picked up sand, rose like a wall and then started propagating as an organized wave". Indeed, the wave field is made by an evanescent component quickly decaying offshore (Fig.…”

“…Note that at both locations the largest wave is never the first one, but is rather shifted towards the middle of the group. This interesting behaviour, also reported in several eyewitness accounts (Tinti et al 2005), results from the absence of a properly defined leading wave along a sloping beach, as shown analytically by Sammarco and Renzi (2008). Note that this delaying effect of the tallest waves is a property of the plane beach bathymetry.…”

“…Such a quick decay of the offshore leading wave in the conical island geometry implies that much of the tsunami energy is still held around the island, whose beach acts as a barrier to partially trap waves. In the following section, we shall comment on the dynamics of generation and propagation of a tsunami induced by a double Gaussian landslide around a conical island, resembling the 2002 event at Stromboli (Tinti et al 2005).…”

Stromboli – the best place to actively learn and understand the behavior of an active volcano and its processes

“…Such example is a landslide event on 30th of December 2002, when 5 min after this event, the first tsunami wave struck the westernmost part of the village of Stromboli, with a maximum run-up of about 10 m (Tinti et al, 2005). The maximum flooding (100 m inland) occurred in the north-eastern lowland sector of the island, causing extensive damage to infrastructure.…”

“…The slides may also produce tsunami waves lasting for several minutes (Tinti et al, 2005). Such example is a landslide event on 30th of December 2002, when 5 min after this event, the first tsunami wave struck the westernmost part of the village of Stromboli, with a maximum run-up of about 10 m (Tinti et al, 2005).…”