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The strongest documented seismic disaster ever occurred in the Po Plain area (January 3, 1117, M = 6.5) involved significant damage over a large zone. The genetic mechanism of such an event, most probably caused by more than one earthquake, is still an object of debate. Above all, the sources so far proposed cannot account for significant features of the observed macroseismic field. In this work, we suggest that the damage in the Verona zone was caused by the activation of a fault in the Lessini tectonic district, while damage in the central Po Plain may be related to a thrust fault located beneath the Giudicarie belt. The effects felt in northern Tuscany might derive from the seismic activation of the presumed SW-ward buried prolongation of the Giudicarie fault. The presence of such transpressional lithospheric discontinuity in the Adriatic domain since the upper Miocene and its reactivation (Pliocene-Pleistocene) as a thrust zone is mainly suggested by an accurate analysis of the observed deformation pattern in the central Mediterranean region. The proposed Giudicarie source may also help to explain the damage observed in the central Po Plain on December 25, 1222, which is not compatible with the seismic sources so far proposed.

The observed deformation pattern in the central-western Mediterranean area, in particular the development of the Northern, Central and Southern Tyrrhenian basins in three well distinct phases, can hardly be explained as an effect of the gravitational sinking of subducted lithosphere, a hypothesis often advanced in literature. A more plausible and coherent explanation of the spatio-temporal distribution of major tectonic events in the study area can instead be achieved by supposing that tectonic activity has mainly been driven by the convergence of Africa and Eurasia and the roughly westward displacement of the Anatolian-Aegean-Pelagonian belt. The development of Arc-Trench-Back Arc systems is interpreted as an effect of extrusion processes, that in some constricted contexts have represented the most convenient shortening process for accommodating plate convergence.

A statistical analysis of the relations between macroseismic intensity and magnitude is presented. The examined data set contains earthquakes characterized by epicentral or maximum intensity ≥ VI which occurred in the Mediterranean region. As a first step, an empirical magnitude-intensity relationship has been determined by using the whole data set. Then, differences between experimental magnitude values and the ones expected on the basis of the empirical relationship have been correlated with some features related both to physical and data sources characteristics. On this basis, a distribution-free statistical approach has been developed to attempt a regionalization of the examined area, able to locally optimize the performances of magnitude-intensity relations. However, the results showed that data relative to larger events (intensity ≥ VII) are not sufficient to perform any reliable zonation of the area. Thus, well-constrained relationships determined for the whole Mediterranean region should be preferred to ill-defined local ones. Concerning smaller earthquakes (intensity VI), the analysis suggests that an efficient zonation could only be obtained if medium-scale variations (lower than 200 Km) are taken into account.

It is widely believed that the Africa-Eurasian relative motion in the Mediterranean region is oriented SE-NW to S-N. This result has been deduced from the analysis of North Atlantic kinematic data by assuming that Eurasia is a unique coherent plate from the North Atlantic ridges to the Pacific trenches. However, this assumption cannot easily account for the not negligible tectonic activity inside and around Western Europe (Rhine Graben system, Pyrenees and off-shore Portugal). This paper shows that, if one allows Western Europe to move independently from main Eurasia, the kinematic indicators in the North Atlantic do not exclude other kinematic solutions which are significantly different from those currently accepted. In particular, it is demonstrated that a SSW-NNE to SW-NE trending Africa-Eurasia convergence, beside allowing plausible explanations of major post-Tortonian deformation events in the Central Mediterranean region, can fit North Atlantic data within experimental errors.

International audience; We argue that the study of long-range interaction between seismic sources in the peri-Adriatic regions may significantly contribute to estimating seismic hazard in Italy. This hypothesis is supported by the reconstruction of the geodynamic and tectonic settings in the Central Mediterranean region, the space–time distribution of major past earthquakes, and the quantification of post-seismic relaxation. The most significant evidence of long-distance interaction is recognized for the Southern Apennines, whose major earthquakes have almost regularly followed within a few years the largest events in the Montenegro-Albania zone since 1850. Statistical analyses of the post-1850 earthquake catalogues give a probability of about 10% that a major event in the Southern Apennines is not preceded by the occurrence of a strong event in the Southern Dinarides–Albanides within 3–5 years. Conversely, the probability of false alarms is relevant (50% within 3 years, 33% within 5 years). Northward, the tectonic setting and some patterns of regularity seen in major events suggest that the seismic activation of the main transtensional decoupling shear zones in the Central Apennines should influence the probability of major earthquakes in the Northern Apennines.

In this paper we present observations of crustal motion related to a largeGPSnetworklocated in the central‐western Mediterranean area. Velocities are obtained by the analysis of more than 30 observing sites at which at least three different GPS campaigns were carried out in the time span 1991–1999. The results are presented both in the ITRF96 reference frame and with respect to a Eurasian fixed reference frame. The siteslocated along the northern African margin, in Sicily and southern Italy show prevalentnortheastward movements with a mean velocity of roughly 0.7 cm yr −1 . The relatively dense network available in the southern Apennines led us to try a tentative estimate of the average strain rate in this zone, resulting in a maximum extension of 0.021 ± 0.006 × 10 −6 yr −1 normal to the chain. In Ionian Greece the two sites located south of the Kephallinia discontinuity (Lefkas and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr −1 .

Summary The uncertainty that may affect seismic strain estimates in the Mediterranean is investigated using a distribution-free numerical approach based on the bootstrap resampling technique, applied to more than 2000 seismic source mechanisms of shallow earthquakes that occurred from the Azores to Iran in the period 1905–1999. This analysis shows that the short time interval covered by the available data set may be the main source of uncertainty on long-term strain estimates, since it could imply a biased representation of contributions from large earthquakes. Our results also indicate that, as a possible consequence of this bias, the condition of strain field uniformity is poorly verified in most of the zones considered. The confidence limits obtained for scalar strains and directions of principal strain axes indicate that both the amount and the style of seismic deformation are poorly defined for roughly half of the zones considered, mostly located in the western and central Mediterranean area. These results suggest that one should be cautious in using seismic strain estimates when not accompanied by satisfactorily uncertainty evaluation.

The highly heterogeneous strain field indicated by neotectonic and seismological data in the central-eastern Mediterranean region has been reproduced, at a first approximation, by finite element modelling, of a 2D elastic thin plate. The zone considered is modelled as a mosaic of poorly deformable zones decoupled by highly deformable belts, simulating the major tectonic structures indicated by geological and geophysical evidence. The deformation of the model is obtained by imposing kinematic boundary conditions, representative of the motion of Africa and eastern Anatolia relative to Eurasia. Experiments carried out with different boundary conditions and model parameterisations have provided information on the sensitivity of the model and some insights into the geodynamic behavior of the study area. The deformation pattern of the central Mediterranean area is strongly conditioned by the mechanical properties assumed in the border zones between the Aegean and Adriatic systems. The match of the complex strain pattern observed in the western Anatolian–Aegean–Balkan zones is significantly favoured if high rigidity is assigned to the inner part of this structural system. A motion of Africa with respect to Eurasia compatible with an Eulerian pole located offshore Portugal best accounts for the observed strains in the central Mediterranean region. The match of the strongly heterogeneous strain field observed in the study area can hardly be achieved by simplified models not including major tectonic features and lateral heterogeneity of mechanical properties. The kinematic field resulting from the model configuration which best simulates the observed strain field presents some differences with respect to geodetic measurements in the Aegean–Western Anatolian area, where the computed velocities are systematically lower than the geodetic ones. It is suggested that the most plausible explanation of such differences is related to the fact that the present deformation pattern, inferred from geodetic data, may be different from the middle–long term one, inferred from seismological and geological data.

A list of major constraints to impose on evolutionary reconstructions of the Central-Eastern Mediterranean region for the middle Miocene period to the Present is proposed. Each constraint is constituted by a tentative description of the deformation and related tectonic regime which affected major active zones during each evolutionary phase. This information has been derived from the analysis of the available observations in the various branches of Earth Sciences, trying to select clearly recognized deformations, possibly supported by independent observations. The list here reported has been used to constrain the evolutionary reconstruction proposed by Mantovani et al.(1997).

Seismological investigations have provided an estimate of the gross structnral features of the crust/upper mantle system in the Mediterranean area. However, this information is only representative of the short-term me- chanical behaviour of rocks and cannot help us to understand slow deformations and related tectonic processes on the geological time scale. In this work strength envelopes for several major structural provinces of the Mediterranean area have been tentatively derived from seismological stratification and heat flow data, on the assumption of constant and uniforrn strain rate (10-16 S-1), wet rocks and conductive geotherm. It is also shown how the uncertainties in the reconstruction of thermal profiles can influence the main rheological prop- erties of the lithosphere, as thickness and total strength. The thickest (50-70 km) and strongest mechanical lithospheres correspond to the coldest zones (with heat flow lower than or equal to 50 mW m-2), i.e., the Io- nian and Levantine mesozoic basins, the Adriatic and Eurasian foreland zones and NW Greece. Heat flows larger than 65 mW m-2, generally observed in extensional zones (Tyrrhenian, Sicily Channel, Northern Aegean, Macedonia and Western Turkey), are mostly related to mechanical lithospheres thinner than 20 km. The characteristics of strength envelopes, and in particular the presence of soft layers in the crust, suggest a reasonable interpretation of some large-scale features which characterize the tectonic evolution of the Central- Eastem Mediterranean.

Some considerations are reported on the tectonic setting and microplate mosaic in the Mediterranean zones where VLBI and SLR stations are located. In particular, the possible sources of ambiguity in the determination of the Africa-Eurasia and Adriatic-Eurasia relative motions from geodetic data are discussed. Possible alternative kinematic interpretations, with respect to those reported in the literature, are then proposed.

The tectonic activity which has occurred in the Central Mediterranean since the late Tortonian is explained as a result of the Africa-Eurasia convergence roughly along a SSW-NNE direction. This convergence has been first accommodated by a considerable reduction of the Adriatic foreland, through the consumption of its eastern and western margins, and then by the lateral escapes of crustal wedges, accompanied by crustal thickening, in the zone comprised between the Adriatic and African forelands. The lateral escapes of the Calabria and Sicily blocks, towards SE and NW respectively, have been allowed by the presence, at the sides of the most strongly compressed zone, of poorly constrained boundaries, corresponding to the thinned Ionian foreland and, to the zone of crustal stretching in the Tyrrhenian basin. This interpretative scheme allows physically plausible explanations of a considerable amount of geological, geophysical and volcanological evidence in the framework of relatively simple and coherent tectonic mechanisms.

The post-Tortonian deformation pattern in the Central Mediterranean can be satisfactorily interpreted in the framework of a SSW-NNE to SW-NE convergence between Africa and Eurasia (Mantovani et al., 1992 and this volume). However, this hypothesis is not in line with the most widely used Africa-Eurasia kinematic models, based on the analysis of North Atlantic kinematic data, which predict a SE-NW to S-N motion between Africa and Eurasia. Here it is argued that these models might be not reliable, since are based on the assumption that Eurasia is a unique coherent block from the Atlantic ridges to the Pacific trenches, which can hardly account for the significant intraplate deformation occurring in Western Europe, and in particular, in the Iberian peninsula and surrounding regions. This evidence would imply that the kinematic data observed along the Mid-Atlantic ridges just North of Azores and those on the Azores-Gibraltar belt cannot be used to constrain the relative motions of Eurasia with respect to North America and Africa respectively. It is shown by quantitative computations that the remaining kinematic data in the North Atlantic can be reconciled, within errors, with a NNE to NEward motion of Africa with respect to Eurasia, in the Central Mediterranean. This kinematic pattern does not involve any significant difficulty in explaining the tectonic pattern in the other sectors of the Mediterranean area and along the boundaries of the Eurasian continent.

It is argued that the Plio-Quaternary deformation pattern in the Mediterranean region is compatible with a SSWNNE convergence between Africa (Nubia) and Eurasia and that the significant difference between this kinematics and the one provided by global models (SSE-NNW convergence e.g., the NUVEL-1) may be due to the fact that those models interpret North Atlantic data by adopting an oversimplified two-plate configuration, which cannot account for the occurrence of significant seismotectonic activity inside the presumed Nubia and Eurasia blocks. It is shown that the adoption of a new plate configuration involving the Iberia and Morocco microplates, strongly suggested by geological and seismotectonic evidence, makes it possible to identify a kinematic model compatible within errors with the constraints recognized in the Mediterranean region and with the NUVEL-1 North Atlantic data set. Some considerations are made about why the present-day Nubia-Eurasia kinematic models inferred from geodetic observations are significantly different from long-term models, such as model NUVEL- 1 and the one proposed in this work.

Introduction. Some current problems on the tectonic evolution of the Mediterranean during the Cainozoic A.M.C. Sengor. Rates of active deformation in the Eastern Mediterranean J. Jackson. Post-Tortonion deformation pattern in the Central Mediterranean: a result of extrusion tectonics driven by the Africa-Eurasia convergence E. Mantovani, D. Albarello, D. Babbucci, C. Tamburelli. Africa-Eurasia kinematics in the Mediterranean: an alternative hypothesis D. Albarello, E. Mantovani, D. Babbucci, C. Tamburelli. Tectonic evolution of the Northern Arabian Plate in Western Syria M. Barazangi, D. Seber, T. Chaimov, J. Best, R. Litak, D. Al-Saad, T. Sawaf. The tectonic regimes along the convergent border of the Aegean Arc from the late Miocene to the present southern Peloponnesus as an example J.L. Mercier, D. Sorel, S. Lalechos, B. Keraudren. Tyrrhenian basin and Apennines kinematic evolution and related dynamic constraints E. Patacca, R. Sartori, P. Scandone. Neogene basins in the Strait of Sicily (Central Mediterranean): tectonic setting and geodynamic implications A. Argnani. Seismological studies of upper mantle structure below the Mediterranean with a regional seismograph network A. Morelli, S. Mazza, N.A. Pino, E. Boschi. The determination of earthquake size and source geometry in Mediterranean Sea D. Giardini, B. Palombo, E. Boschi. Tectonic and seismic processes of various space and time scales in the Greek area G.A. Papdopoulos. A review of the Eastern Alps - Northern Dinarides seismotectonics D. Slejko. Regional stresses in the Mediterranean region derived from focal mechanisms of earthquakes A. Udias, E. Buforn. Source process of some large earthquakes in Greece and its tectonic implication J. Drakopoulos, G.N. Stavrakakis. Recent seismic activity andearthquake occurrence along the Apennines M. Cocco, G. Selvaggi, M. Di Bona, A. Basili. P-wave teleseismic tomography contribution to the delineation of the upper mantle structure of Italy G.B. Cimini, A. Amato. Geological and seismological evidence of strike-slip displacement along the E-W Adriatic--Central Apennine belt P. Favali, R. Funiciello, F. Salvini. Stable fault sliding and earthquake nucleation M. Dragoni. Paleomagnetism in the Mediterraneum from Spain to the Aegean: a review of data relevant to Cenozoic movements E. Marton. Use of the Paleomagnetic databases for geodynamical studies: some examples from the Mediterranean region G. Scalera, P. Favali, F. Florindo.