The aim of this study was to provide a contribution to seismic hazard assessment of the Salento Peninsula Apulia, southern Italy. It was also widely felt in the western coast of Greece, in Malta Islands, in southern Italy and in some localities of central and northern Italy.

Moreover, the area of the Salento Peninsula has also been hit by several low-energy and a few high-energy earthquakes over the last centuries; the instrumental recent seismicity is mainly concentrated in the western sector of the peninsula and in the Otranto Channel. Accordingly, a critical analysis of several documentary and historical sources, as well as of the geologic—geomorphologic ground effects due to the strong Salento earthquake, has been carried out by the authors in this paper; the final purpose has been to re-evaluate the MCS macroseismic intensities and to provide a list of newly classified localities according to the ESI scale on the base of recognized Earthquake Environmental Effects.

The result is a quite different damage scenario due to this earthquake that could raise the seismic potential currently recognized for the Salento area, and consequently upgrade the seismic hazard classification of the Salento. Indeed it is important to remind that currently, despite the intense earthquake activity recorded not only in the Otranto Channel, but especially in Greece and Albania, this area is classified in the least dangerous category of the Seismic Classification of the Italian territory IV category.

The Salento area has also suffered destructive seismicity of the Gargano Promontory northern Apulia , of the Southern Apennines chain and of the Calabrian Arc, in Italy. Nevertheless, this area is actually included in the IV category of the Italian Seismic Classification; this category is the least dangerous, in fact municipalities of this area have a low probability of seismic damages.

According to the Ordinance of President of the Council of Ministers no. In order to contribute, on the basis of a detailed study of the earthquake, to an updated evaluation of the seismic hazard of the Salento area, currently underestimated, the following matters have been examined:. Historical and recent seismicity of the Apulia region and particularly of the Salento Peninsula from available catalogues Guidoboni et al. As regards the methodology of earthquake intensity assessment, the traditional MCS scale and the new macroseismic scale ESI have been applied in this paper Gaudiosi et al.

The intensity evaluated through the MCS scale is a major seismic hazard parameter because is not only used for the description of earthquake effects, but it also describes the damage pattern. This scale integrates the traditional macroseismic scales, of which it represents an evolution, allowing to assess the intensity parameter exclusively on the basis of environmental effects, also where buildings are absent, and when diagnostic elements damage-based have saturated.

The main advantage of the ESI scale is the classification, quantification and measurement of several known geological, hydrological, geomorphologic and botanical features that are associated with each intensity degree. This scale has been tested worldwide, in the case of several modern, historical earthquakes and paleoearthquakes Silva et al. Based on the above-mentioned seismic intensities scales, the reassessment of both the macroseismic effects on man-made structures and the triggered effects in the natural environment have allowed to elaborate a quite different scenario of the earthquake, leading to other intensity values for some localities and increasing the number of the newly classified localities, represented in this paper with a new intensity map.

The Apulia region southern Italy , NW—SE elongated, represents the emerged part of the Adriatic foreland domain, shared by the Apennines chain to the west and the Dinarides—Albanides—Hellenides chains to the east Caputo et al. The geodynamic background of this area, located in the central sector of the Mediterranean basin, shows complex tectonics since it is a plate boundary collision zone Fig. Such compressional regime is still active and featured by frequent and strong seismicity occurring mostly in the Ionian Sea and western Greece Slejko et al.

Apulia seismotectonic map. Structural map: simplified from Ambrosetti et al. In the framework of the Mediterranean basin tectonic evolution, the relative motion of the Adriatic foreland respect to the African plate is still under debate; particularly many geological and geophysical data point out an independent Adriatic microplate, moving by counter-clockwise rotation, which deformation shows different pattern near its borders Argnani et al.

In Fig. Moreover, major E—W strike slip fault zones divide Apulia into structural blocks behaving independently, the Gargano Promontory, the Murge Ridge and the Salento Peninsula. The spatial distribution of earthquakes shows different pattern of seismic activity inside these three zones, and some of the mapped faults are presently active Fig. The outcropping rocks of the Apulian foreland are prevalently limestone-dolomite units belonging to the Apulia platform, with carbonatic-terrigenous marine deposits at the top of the stratigraphic sequence, Middle Eocene—Upper Pleistocene age Mastronuzzi et al.

According to Ambrosetti et al. The seismic history of Apulia and surrounding regions has been analyzed consulting the available catalogues on the INGV Web site. In the CPTI11, when both macroseismic and instrumental seismic parameters are available, the epicenter is selected according to expert judgment.

Magnitude of instrumental data after is obtained from moment tensor or spectral method M w , while magnitude of macroseismic data before is a weighted mean of previous magnitude values calculated from magnitude—intensity empirical relations Rovida et al.

This catalogue lists earthquakes occurred in Italy between BC and , and earthquakes occurred in the Mediterranean area between the eighth century BC and the sixteenth century. The whole data from this catalogue are based on ad hoc historical investigations and on new interpretations of historical seismic sources. It includes also the data of past instrumental seismicity from the Italian Seismic Bulletin that listed the earthquakes recorded by the Italian National Seismic Network since The historical seismicity of Apulia and neighboring areas and instrumental seismicity from to are shown in Fig.

The historical and recent seismicity of the Apulia region is characterized by a higher frequency of earthquakes in the northern sector Gargano , than in the southern one Murge, Salento Fig. The Salento Peninsula has been generally considered almost aseismic.

It is a common opinion that the seismic hazard of this area is exclusively associated with damage caused by sources from the Ionian Sea and from the eastern side of the Adriatic Sea, including the Hellenic Arc. In particular, the Salento region is close to areas with frequent and intense seismicity; in fact it is less than km far from Albanian and Greek coasts where many energetic earthquakes occurred and are strongly felt in the Salento Peninsula.

For example, the It was also widely felt in Malta Islands, in southern Italy and in some localities of central and northern Italy. The total number of casualties is undefined, probably several hundreds. The most striking effect of this earthquake was a large tsunami on the Salento coasts Mastronuzzi et al. However, the location and geometry of the seismogenetic source of the Salento earthquake is still a subject of scientific debate and will be discussed later.

This area suffered other strong earthquakes as suggested by Pieri et al. However, the internal part of the Salento shows a minor, but not negligible, seismic activity Tables 2 , 3 ; Fig. The instrumental seismicity in the Murge and in the Salento Peninsula is characterized by scattered seismicity of low energy, mainly concentrated in the western sector of Salento, in the Gulf of Taranto and in the Otranto channel.

Low-magnitude earthquakes could not be localized until about 15 years ago due to the small number of seismic stations of the INGV seismic network in the central and southern Apulia. The increase in the number of seismic stations since provides more complete hypocentral determinations of low-magnitude earthquakes, occurring in the Apulia foreland Del Gaudio et al.

The event was felt in the whole Apulia region, in many cities as Napoli, Matera, Reggio Calabria, Messina in southern Italy and even in some localities of central and northern Italy as Parma, Venezia, Vicenza, Trento and Udine Baratta , the last two cities far from the epicentral area more than a km.

This earthquake was also felt in a wide sector of the Mediterranean area causing considerable damage along the western coast of Greece, Albania and Malta Islands Malta and Gozo. It also generated a large tsunami, quoted in many references and databases as the Euro-Mediterranean Tsunami Catalogue Maramai et al.

The February 20, , earthquake was a complex seismic event, consisting in at least three distinct shocks, beginning approximately from According to Ambraseys , there were more shocks over 1 h involving the Ionian Islands. The location and geometry of the seismogenetic source are still a subject of scientific debate, due to the different locations ascribed, respectively, on land Guidoboni et al.

Table 5. The two different epicentral locations with felt reports. Most authors agree on the hypothesis of a seismic source in the Otranto channel Galli and Naso ; Locati et al. The authors of this paper carried out a critical revision of both original archival sources and the most important historical and recent papers, taking into account the macroseismic evaluations of Mercalli , De Giorgi , Baratta , Margottini , , Ferrari , Guidoboni et al.

Many primary sources have been found in the writings of local historians, as De Simone and Camarda , who reported detailed accounts by notaries and witnesses from Salento. In fact at that time , the notary protocols often reported news about the extraordinary events occurred in their regions.

Other information from the Vatican archives are reported in Guidoboni et al. Significant damages were reported also in the nearby town of Preveza, in other villages of inland Greece, Albania and Malta Margottini , ; Galea ; Galli and Naso In this paper, a revaluation of the earthquake MCS intensity for the damaged localities has been carried out on the basis of historical documents of contemporary witnesses, as Cagnes and Scalese , Leo , Forleo , De Soldanis and Saracino found both in private and public archives, in historiographical books De Giorgi ; De Simone ; Camarda , and in the recent scientific literature Margottini , ; Ferrari ; Galea ; Galli and Naso ; Guidoboni et al.

In addition, for some localities local historiographical Web sites have been also consulted. The assessment of the macroseismic degree has been made using the traditional MCS scale. Moreover, for a more complete evaluation of this event, the indirect geomorphologic data referable to environmental earthquake effects have been utilized to evaluate the intensity according to the ESI scale.

For both MCS and ESI scales, the authors have decided to assign a well-defined unique intensity value for each locality, based on the collected data and on their professional judgment. In this study, the new MCS intensities have been assessed for 18 localities, mainly in the Salento Peninsula.

In Table 6 , the MCS revaluated intensity values with a brief description of the felt reports, the damage level, the main archival sources and the recent literature consulted, are listed. Many coeval accounts attest the high degree of damage suffered by the town and the high number of deaths Table 6. English translation of original text : The last Wednesday, at approximately The motion, however, was wavelike and horizontal, so neither happened the minimum pain, nor any damage.

For a comprehensive evaluation of the earthquake, it is essential to take into account both the direct information derived from archival and historical sources and also the geomorphologic data concerning the Environmental Earthquake Effects EEEs.

Although for this earthquake the primary effects such as faults, uplift, subsidence phenomena have not been clearly recognized, neither in the ground nor in the seabed, this event triggered several secondary effects. Other secondary effects are represented by hydrological changes, landslides, liquefaction phenomena and ground cracks Table 7. In Table 7 , the new classified localities are listed together with a brief description of the observed EEEs, by coeval chroniclers, and the main relative references.

The earthquake triggered a high-energy tsunami that produced devastating effects on the coasts of the Salento Peninsula Maramai et al. The tsunami effects are evidenced both by historical accounts Fig. Chronicle of the February 20, , event, written by the mayors of Brindisi Italy.

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