[1] From Gibraltar to Anatolia, the active tectonics in the Mediterranean is studied by means of an integrated approach based on geophysical, geodetic, and seismological methodologies. The aim of this study is to gain a deep insight into the kinematics and dynamics of the crustal and lithospheric processes affecting the Mediterranean. Major tectonic processes, such as continental collision and subduction, characterize this region, which marks a broad transition zone between the African/Arabian and Eurasian plates. A thin-shell finite element approach allows us to simulate the deformation pattern in the Mediterranean, from 10°W to 40°E and from 30°to 50°N. The global plate motion model NUVEL-1A is used to account for the convergence, while the relative velocities of the overriding and subduction plates are obtained from another family of models. These models simulate the effects of the negatively buoyant density contrasts of the subducted lithosphere on the horizontal velocity at the surface. A systematic comparison between model results and the seismic strain rates obtained from the National Earthquake Information Center catalog, the geodetic velocity field and strain resulting from GPS, satellite laser ranging, and very long baseline interferometry analyses and the World Stress Map, indicate that Africa/Arabia versus Eurasia convergence and subduction in the Aegean Sea and Calabrian Arc are the major tectonic mechanisms controlling the deformation style in the Mediterranean. It is shown that in order to carry into coincidence the modeled and the seismic strain rate patterns and the geodetically retrieved strain rate tensors, a deep subduction in the Aegean Arc must be included in the modeling.

Abstract. In the framework of the European SCenarios for tsunami Hazard-induced Emergencies MAnagement (SCHEMA) project (www.schemaproject.org), we empirically developed new tsunami damage functions to be used for quantifying the potential tsunami damage to buildings along European-Mediterranean coasts.Since no sufficient post-tsunami observations exist in the Mediterranean areas, we based our work on data collected by several authors in Banda Aceh (Indonesia) after the 2004 Indian Ocean tsunami. Obviously, special attention has been paid in focusing on Indonesian buildings which present similarities (in structure, construction material, number of storeys) with the building typologies typical of the EuropeanMediterranean areas.An important part of the work consisted in analyzing, merging, and interpolating the post-disaster observations published by three independent teams in order to obtain the spatial distribution of flow depths necessary to link the flowdepth hazard parameter to the damage level observed on buildings. Then we developed fragility curves (showing the cumulative probability to have, for each flow depth, a damage level equal-to or greater-than a given threshold) and damage curves (giving the expected damage level) for different classes of buildings. It appears that damage curves based on the weighted mean damage level and the maximum flow depth are the most appropriate for producing, under GIS, expected damage maps for different tsunami scenarios.

International audience[1] We study the seismicity and stress transfer in the Coquimbo region of central Chile, where an exceptional series of more than 12 earthquakes of magnitudes from 6 to 7.6 has occurred since July 1997. In this area, the oceanic Nazca plate is subducted under the continental lithosphere of South America. Below 50 km, the downgoing slab slips aseismically with respect to the South American plate at a rate close to 6.5 cm/yr. The Coquimbo region was the site of major earthquakes of M > 8 in 1880 and 1943. After many years of quiescence, the seismic activity of the plate interface suddenly increased in mid-1997 and continued at least until 2004. The first group of events occurred in July 1997 in the middle of the locked plate interface. In October 1997, the activity moved inland to the Punitaqui-Ovalle area, just above the transition from the seismogenic zone to that of aseismic slip. The main event of the series was the M = 7.6 15 October 1997 Punitaqui earthquake. This is an intraslab compressional earthquake that occurred at $60 km depth, on a subvertical plane located very close to the downdip edge of the seismogenic coupled interface. We performed simulations of Coulomb stress transfer for earthquakes near the bottom of the seismogenic zone. We found that a simple model of stress transfer from the aseismic slip at depths greater than 50 km can explain the triggering not only of the Punitaqui earthquake but also of the July 1997 sequence. Additional simulations show that the seismicity that followed the 1997 event for almost 7 years can also be simply explained as a result of increased Coulomb stresses on the seismogenic plate interface as a result of the 1997 event and aseismic slip

SUMMARY In central Mexico some significant normal faulting events have occurred within the subducted oceanic Cocos plate, just below or near the down‐dip edge of the strongly coupled interface. These normal faulting shocks followed large shallow thrust earthquakes. In other subduction zones such events generally precede the up‐dip thrust events. A vertical 2‐D finite element modelling has been used to simulate the subduction of the Cocos plate beneath the North American plate when the slab is driven by an active convergence velocity or slab pull. We find that the latter mechanism plays only a minor role due to shallow subduction. The modelling results show that the stress pattern is very sensitive to the geometry of the plates. In particular, normal faulting earthquakes that follow large thrust events can be explained on the basis of the flexural response of the overriding and subducting plates to the peculiar geometry of this subduction zone, where the subducting slab becomes horizontal at about 100 km from the trench. This horizontal part of the subducting plate, down‐dip with respect to the main thrust zone, is under an extensional stress field. This provides an alternative explanation to the slab pull for the occurrence of normal faulting intraplate earthquakes. In order for normal faulting earthquakes to occur in the early part of the seismic cycle, it is necessary that the large up‐dip thrust events have a partial stress drop. We find that for small fractional stress drop, a wide region of extension remains below the down‐dip edge of the main fault plane following a large thrust earthquake. Thus, the main thrust earthquakes do not invert the polarity of the active stress field, which is compressional and extensional up‐dip and down‐dip, respectively, with respect to the main thrust fault. Larger fractional stress drops result in larger delays in the occurrence of normal faulting events after the main thrust events.

Abstract. Within the framework of the SCHEMA FP6 EC co-funded project (http://www.schemaproject.org), we have identified the sources of errors/uncertainties that can be introduced at several steps of the damage assessment process, from post-disaster field measures up to hazard and damages maps production. Errors, for instance, are introduced when collecting post-disaster observations owing to different types of instruments/methods, water marks considered, tide correction, etc.: in extreme cases, differences of meters can be found between water heights data published by different teams for the same locations. Much uncertainty comes from difficulties in identifying and characterizing the potential tsunami sources and from numerical modelling. Moreover, the resolution of the employed Digital Terrain Models can noticeably affect the predicted inundation extent. We have also verified that the consistency of the computations on the long term varies sensitively depending on the code, raising the problem of results reliability for emergency management in dangerous coasts exposed to repeated waves. In addition, damage assessment is performed using damage functions linking the mean damage level on buildings with the maximum water elevation measured in the field without considering other tsunami parameters such as stream velocity. Finally, we examined uncertainties introduced in hazard and vulnerability mapping due to cartographic processing.

The active tectonics of the Western Alps reveals contrasting regimes: ongoing extension at the heart of the chain and transpression-compression at its external sectors. The active processes currently affecting this region are still a matter of debate. The classical models proposed in the literature invoke: Eurasia-Adria plate collision, counterclockwise motion of the Adria microplate, slab retreat of the subducted continental lithosphere and slab-detachment. More recently, several authors prefer the hypothesis of tectonics driven by isostasy-buoyancy forces. To better understand the influence of these processes on the velocity, strain and stress fields at the surface and in the crust, we developed 2D viscoelastic numerical models along a vertical cross-section perpendicular to the Western Alps. We run our models with different driving forces in order to investigate, one by one, the geodynamic processes proposed in the literature. Results are compared with available geodetic, geological and seismotectonic data. In order to bring into coincidence model predictions and observations, an important vertical isostatic readjustment must be included in the modelling, together with a slight horizontal compression (0.5 mm year 21 ), probably due to Africa-Eurasia convergence. We show that the subduction process in this Alpine region is likely to be dead and that buoyancy forces may be dominating the present-day tectonics.

S U M M A R YFor the central Apennines, peninsular Italy, a series of tectonic mechanisms are reproduced by means of finite-element models, in order to study the effects of active tectonics on the seismic cycle in the Umbria-Marche seismogenic zone. Continental extension and rift push effects induced by small-scale convection are modelled within 2-D viscoelastic models of the crustlithosphere system, in vertical cross-sections perpendicular to the strike of the major tectonic structures under study, namely the Apennines and the Colfiorito fault zone, where the 1997 seismic sequence took place. With the aim of constraining the active tectonic mechanisms at the regional scale and the behaviour of the fault in the seismogenic zone at the local scale, modelled baseline rate of change are compared with newly acquired GPS data, retrieved from the two permanent GPS receivers of Camerino (CAME) and Elba (ELBA), deliberately installed along the modelled transect. These receivers are located at both edges of the continental extension in the front of the Apennines, close to the Adriatic Plate in the east, and in the rear of the chain, in the Tyrrhenian domain. The deformation pattern inferred from seismicity and from the geodetic data is consistent with small-scale convection in the Tyrrhenian domain, which reproduces extension in the rear of the Apennines and compression in the front of the chain. A convective mechanism, associated with backarc opening and doming of the asthenosphere, provides an extensional rate, along a baseline connecting two sites in the front of the chain (Camerino) and in its rear (Elba), comparable to the observed baseline rate of change. The viscosity of the lower crust plays a fundamental role in determining the style of stress in the crust-lithosphere system. Once constrained by means of the extensional baseline rate inferred from GPS, the modelled slip across the Colfiorito fault and the modelled earthquake recurrence time are consistent with the 1997 normal fault event and with palaeoseismicity, respectively.