RICERCA ITALIANA     

Analysis of risk from tsunamis in the Calabrian Arc and in the Adriatic sea

Università degli Studi di Bologna

Abstract

The project proposes a multidisciplinary approach to study the active tsunamigenic seismic faults of the Calabrian Arc (CA) and of the Adriatic Sea (AS) regions, and to identify and to analyse plausible scenarios of risk. The working team possesses the required expertise to investigate active faults from the viewpoint of their morpho-structural and seismotectonic characterisation (such as structural geology, seismology, historical and macroseismic seismology) as well as the technical knowledge needed to study tsunami generation by earthquakes and by mass failures (seismology, geotechnical geology and engineering) and to investigate tsunami impact on coasts and on coastal structures (oceanography, geomorphology). The chief motivations of this research are: 1a) the CA is the Italian region with the highest rate of large earthquakes and tsunamis, it is crossed by a system of normal faults striking as the mountain range, and by transcurrent faults cutting normally the chain; 1b) transcurrent faults and some of the normal faults continue into the sea (south Tyrrhenian and Messina strait); 1c) the main system of faults off eastern Sicily is associated with the Hyblean-Malta escarpment, and other relevant faults are near-shore and intersect the coast; 1d) the present morpho-structural knowledge of all the above faults is incomplete; 1e) there is uncertainty on the source fault of several tsunamigenic earthquakes; 1f) the potential of tsunami generation by mass failures triggered by >>>

Principal Investigator

Stefano TINTI Università degli Studi di BOLOGNA

Research Objectives

The main goal of the project is to identify and to characterise the most important submarine active faults in the regions of the Calabrian Arc (CA) and of the Adriatic Sea (AS) with the purpose of assessing the related risk. These regions have different tectonic styles, but have similar features that give us the motivations to study them together. These are: 1) from catalogues of historical events it is known that both regions have been hit by destructive earthquakes repeatedly that in turn caused disastrous tsunamis; 2) seismic sources are placed near shore and often involve the coastal zone; 3) earthquakes are able to offset the sea floor as well as to mobilise marine or coastal sediments with consequent changes of the coastline position; 4) the involved marine basins have complex morphology with presence of structures that tend to trap tsunami energy even with formation of edge waves and to amplify their effects (e.g. Messina Straits, Gargano promontory, Strait of Otranto); 5) existence of coastal basins capable of preserving traces of paleotsunami inundations (e.g. lakes of Lesina and Varano in northern Gargano, lake of Ganzirri, close to Messina); 6) the involved areas have a paramount socio-economic value since development concentrated mainly in a narrow coastal belt for historical tradition and also for recent trends (over 60% of the economic activities of Calabria and eastern Sicily are carried out in the coastal zone where more than 50% of the population lives >>>

First Results

CALABRIAN ARC
Identification of the active faults, discrimination between regional and local deformation and assessment of long-term and short-term (Holocene) deformation rates, with special attention to the structures of Capo Vaticano towards the Tyrrhenian sea, to the high of Palmi-Bagnara and to the structures of the Peloritani range bordering the Ionian sea. Identification of possible paleotsunamis through paleoseismological investigations and analysis of stratigraphic anomalies. Recognition of coastal mass failures associated with large earthquakes. Seismic characterisation of the region with association of structures to seismicity pattern. Acquisition of geomorphological, bathymetric data as well as data on the urban, commercial and industrial structures in areas that are exposed to tsunamis, finalised to the numerical simulations of tsunamis and to the computations of inundation. Delineation of disaster scenarios. Numerical simulations of the scenario events. Maps of maximum inundation expected in relevant areas. Assessment of tsunami risk for the selected scenarios.
ADRIATIC SEA
Identification of active interplate and intraplate sources. Characterisation of their tsunamigenic potential. Re-examination of the catalogues of tsunamis, especially for the eastern coasts of the basin. Identification of possible paleotsunamis by means of geomorphological investigations, coring and dating of core samples. Determination of frequency and intensity of >>>

Timescale

24 months

National and international background

PRESENT KNOWLEDGE ON THE CALABRIAN ARC
The Calabrian Arc (CA) is a structure belonging to the Mediterranean orogenic belt, and connecting the Maghrebides to the Appennines. The geodynamical evolution of this region is complex. Geological and geophysical data suggest that in the last 0.7 Myrs the geodynamical evolution of the CA is characterised by vertical motion (Pirazzoli et al., 1997; Stewart et al., 1997; Bordoni and Valensise, 1998; Antonioli et al., 2003), as well as by movements on the transform faults. The focal mechanisms of recent and historical earthquakes show an extensional mode of deformation, both parallel and perpendicular to the arc (Frepoli and Amato, 2000). Geological data also indicate that extension acts along NE-SW and NW-SE faults since the middle Pleistocene, modelling graben-like structures trending both NE-SW and NW-SE (Tortorici et al., 1995). The main regional feature in this area is given by a prominent normal fault that runs more or less continuously for a total length of 370 km along the inner side of the CA, extending across the Strait of Messina along the Ionian coast of Sicily as far as the Hyblean Plateau. The distinct fault segments are characterised by a very young morphology and control both the major mountain fronts of the region (Catena Costiera, Sila, Serre, Aspromonte, Peloritani, Hyblean Plateau) and the coastline of the southern Calabria and eastern Sicily. Morphological observations and stratigraphic data indicate that >>>