After almost 113 years, the fault that produced the most devastating earthquake of the twentieth century in Europe was discovered, that of 1908 in Messina-Reggio Calabria. Science not only changes the present and helps to build the future in an innovative way, but also makes the past reinterpret with new interpretations. It is also in this perspective that the considerable importance of the discovered in the seabed between Sicily and Calabria of the fault that caused the most serious catastrophe in Europe in the era of instrumental seismology.
December 28, 1908
The earthquake of December 28, 1908 was an event that shook European and world public opinion. The images of apocalyptic destruction have remained in the collective memory. In that case the catastrophe was not only caused by the earthquake, but also by the subsequent tsunami. A new scientific study, published in the international journal Earth-Science Reviews, carried out in a multidisciplinary way sheds light on many aspects of that event. The research was conducted on the seabed of the Strait of Messina and on the seismic-tectonics of the area and is the result of an international collaboration between the Department of Biological, Geological and Environmental Sciences of the University of Catania (Giovanni Barreca and Carmelo Monaco) , the Center for Ocean and Society-Institute of Geosciences of the University of Kiel in Germany (Felix Gross and Sebastian Krastel) and the Etneo Observatory of the National Institute of Geophysics and Volcanology (Luciano Scarfì and Marco Aloisi).
I study
The study reveals, for the first time, the location and geometric characteristics of the possible fault from which the devastating earthquake originated. Already in the title of the study there is the essence of the conceptual meaning of the research: The Messina Strait: Seismotectonic and the Source of the 1908 Earthquake. The study provides a scientific answer and explains the complexity of the phenomena that occurred that morning at 5.20 when a devastating earthquake of intensity XI on the Mercalli scale (estimated magnitude 7.1) changed the history of Messina and Reggio Calabria, bringing real devastation.
Earthquake plus tsunami
The telluric movement made the earth vibrate for more than 30 seconds and led to the complete destruction of the cities of Messina and Reggio Calabria and of numerous other smaller towns, causing the death of over 100,000 people. The earthquake was distinctly felt throughout southern Italy, Montenegro, Albania, but also Greece and Malta and was followed, in less than 10 minutes, from a tidal wave (tsunami) that locally exceeded 10 meters in height. The wave hit the coasts of the Strait adding devastation and death along the coastal areas already severely damaged and where many scared inhabitants had taken refuge. The instrumental seismology was still in its initial phase but the earthquake was nevertheless recorded by numerous seismic stations scattered all over the world which placed its epicenter in the sea along the axis of the Strait of Messina.
The fault
Since that disastrous event, numerous scientific studies carried out by researchers around the world have tried to identify and characterize the tectonic structure responsible for the earthquake – that is, the fault or seismogenic source. Researches that “have produced numerous geological models, often conflicting”, and over the course of many decades have fueled a lively debate in the scientific community “without, however, reaching a scientifically acceptable solution”. The new study has instead, even with sophisticated scientific instruments, reconstructed the complexity of the phenomena with rationality, innovative vision and objective evidence. The research was mainly based on the interpretation of 35 high resolution reflection seismic profiles – as a ‘seabed ultrasound’ – as well as on the analysis of seismological and geomorphological data examined in a multidisciplinary manner. According to the researchers, «the ultrasound of the seabed made it possible to unequivocally identify a deep crack in the seabed of the Strait of Messina. The fault shows evidence of recent activity as it displaces the seabed with slopes up to 80 meters high. The seismic analysis in a 3D environment and geomorphological studies on the ground then made it possible to follow the fault throughout its development, thus obtaining valuable information on its length, a fundamental parameter for estimating the maximum expected magnitude in case of reactivation of the same. but also a comparison with the 1908 event ».
In the Strait
“The structure runs along the axis of the Strait and can be identified about 3 kilometers from the coast of Sicily”, says the scientist Giovanni Barreca, coordinator of the research. «At the latitude of Messina, the rift curves eastwards, penetrating the Calabrian hinterland and then continues along the river course of the Catona stream, a river incision between Villa San Giovanni in the north and Reggio Calabria in the south. The fault is inclined towards the east and reaches a maximum length of 34.5 km. According to length-magnitude relationships, the fault is capable of triggering earthquakes of magnitude 6.9, an energy very similar to that released during the 1908 earthquake. This data, together with the critical analysis of historical sources – for example the distribution of damage and fracturing on the ground, the breaking of a telephone cable between Gallico and Gazzi – and the development of mathematical models of displacement, suggests in fact that the structure tectonics identified is probably the one that more than a hundred years ago caused the most serious seismic disaster of the twentieth century ».
Sicily and Calabria move away
The research also addresses “the controversial issue of the mechanism at the origin of the displacement in progress between Sicily and Calabria – about 3.5 millimeters per year -, identifying its engine in the depths of the crust where a further discontinuity is suspected of favoring the eastward movement of an extensive block of crust comprising the area of the Strait and part of southern Calabria. This movement would occur under the effect of gravity and in an almost aseismic way – that is, not generating high-energy earthquakes – but would encourage the fragile rupture of some more superficial faults, including the cosismic rupture identified in the study, with the release of elastic energy “. The study therefore led to a critical review of the existing literature providing new constraints on the seismic-tectonic of the Strait of Messina, one of the areas with the highest seismic risk in Italy, and above all adds a significant step in the identification of the fault responsible for the earthquake of the 1908. The updated seismic-tectonic model and the location of the possible fault responsible for the great earthquake could, finally, represent a useful basic tool for the safe design of future infrastructures in the area.
May 31, 2021 (change May 31, 2021 | 18:47)
© REPRODUCTION RESERVED