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SUMMARY A seismic hazard map of the territory of India and adjacent areas has been prepared using a deterministic approach based on the computation of synthetic seismograms complete with all main phases. The input data set consists of structural models, seismogenic zones, focal mechanisms and earthquake catalogues. There are few probabilistic hazard maps available for the Indian subcontinent, however, this is the first study aimed at producing a deterministic seismic hazard map for the Indian region using realistic strong ground motion modelling with the knowledge of the physical process of earthquake generation, the level of seismicity and wave propagation in anelastic media. Synthetic seismograms at a frequency of 1 Hz have been generated at a regular grid of 0.2°× 0.2° by the modal summation technique. The seismic hazard, expressed in terms of maximum displacement (Dmax), maximum velocity (Vmax), and design ground acceleration (DGA), has been extracted from the synthetic signals and mapped on a regular grid over the studied territory. The estimated values of the peak ground acceleration are compared with the observed data available for the Himalayan region and are found to be in agreement. Many parts of the Himalayan region have DGA values exceeding 0.6 g. The epicentral areas of the great Assam earthquakes of 1897 and 1950 in northeast India represent the maximum hazard with DGA values reaching 1.2–1.3 g. The peak velocity and displacement in the same region is estimated as 120–177 cm s−1 and 60–90 cm, respectively.

We present an integrated petrological, geochemical, and geophysical model that offers an explanation for the present-day anomalously high non-volcanic deep (mantle derived) CO 2 emission in the Tyrrhenian region. We investigate how decarbonation or melting of carbonate-rich lithologies from a subducted lithosphere may affect the efficiency of carbon release in the lithosphere-asthenosphere system. We propose that melting of sediments and/or continental crust of the subducted Adriatic-Ionian (African) lithosphere at pressure greater than 4 GPa (130 km) may represent an efficient mean for carbon cycling into the upper mantle and into the exosphere in the Western Mediterranean area. Melting of carbonated lithologies, induced by the progressive rise of mantle temperatures behind the eastward retreating Adriatic-Ionian subducting plate, generates low fractions of carbonate-rich (hydrous-silicate) melts. Due to their low density and viscosity, such melts can migrate upward through the mantle, forming a carbonated partially molten CO 2 -rich mantle recorded by tomographic images in the depth range from 130 to 60 km. Upwelling in the mantle of carbonate-rich melts to depths less than 60 -70 km, induces massive outgassing of CO 2 . Buoyancy forces, probably favored by fluid overpressures, are able to allow migration of CO 2 from the mantle to the surface, through deep lithospheric faults, and its accumulation beneath the Moho and within the lower crust. The present model may also explain CO 2 enrichment of the Etna active volcano. Deep CO 2 cycling is tentatively quantified in terms of conservative carbon mantle flux in the investigated area. IntroductionThe role of Earth degassing in present-day global carbon budget and consequent climate effects has been focused chiefly on volcanic emissions (e.g. Gerlach, 1991a;Varekamp and Thomas, 1998, Kerrick, 2001). The non-volcanic 1 escape of CO 2 from the upper mantle, from crustal carbonate rocks, from hydrocarbon accumulations, and from geothermal fields is not considered in the budgets of natural release processes (cf. IPCC reports). However, the impact of these processes on atmospheric CO 2 budget is relevant if considered at the regional scale.Italy constitutes an extraordinary example of massive CO 2 subaerial fluxes in the Western Mediterranean region (e.g. Chiodini et al., 1999Chiodini et al., , 2004Rogie et al., 2000;Chiodini and Frondini 2001;Minissale, 2004). In Italy, CO 2 emissions occur both in those areas of young or active volcanism (e.g. the Tyrrhenian border of Central Italy; Fig. 1), and at zones in which there is no evidence of magmatic activity, such as Central and Southern Apennines (Fig. 1).Interactions between magmas and carbonate rocks at walls of magma chambers locally contribute CO 2 in some recent and active volcanic zones (e.g., Alban Hills, Mt. Ernici, Vesuvius;Federico and Peccerillo, 2002; Iacono Marziano et al., 2007a, b). However, the bulk of present-day soil degassing in Italy is a regional feature affecting both volcanic areas and z...

S U M M A R YThe purpose of this work is to derive a 3-D tomographic image of the shear wave velocity structure of the crust-uppermost mantle in the Aegean area using the group velocities of Rayleigh wave fundamental mode. The database consists of 185 regional earthquakes recorded at broad-band stations that were installed for a period of 6 month in the Aegean area within the framework of a large-scale experiment. In a previous work (Karagianni et al. 2002), an averaged group velocity has been determined using the method of frequency time analysis (FTAN) for each epicentre-station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths. Taking into account additional resolution results obtained for the local group velocities, a grid of 0.5 • was adopted for the Aegean area and a local dispersion curve was defined for each gridpoint. More than 80 local dispersion curves were finally inverted using a non-linear inversion approach, deriving the corresponding 1-D shear velocity models. The interpolation of these models resulted in a 3-D S-wave tomographic image of the crust and uppermost mantle in the broader Aegean area. As expected, as a result of the complex tectonic setting of the Aegean area, strong lateral variations of the S-wave velocities of the crust and uppermost mantle of the studied area are found. In the southern Aegean sea, as well as in a large part of the central Aegean sea a thin crust of approximately 20-22 km is observed, whereas the remaining Aegean sea area exhibits a crustal thickness less than 28-30 km. On the contrary, a crustal thickness of 40-46 km is observed in western Greece along the Hellenides mountain range, whereas in the eastern continental Greece the crust has a typical thickness of approximately 30-34 km.For shallow depths (<10 km) low S-wave velocities are observed under the sedimentary basins of the north Aegean sea, the Gulf of Thermaikos (Axios basin) and western Greece. At depths ranging from 10 to 20 km, low S-wave velocities are mainly found in western Greece under Peloponnesus as well as in Rhodes. This low-velocity zone seems to extend along the Hellenic arc and can be correlated to the Hellenides mountain range and the Alpine orogenesis, in agreement with previous P-wave tomographic results. In the southern Aegean sea very low S-wave velocities (3.6-4.0 km s −1 ) are observed at depths of approximately 30-40 km just below the Moho discontinuity, while in the rest of the inner Aegean sea and continental Greece the uppermost mantle is characterized by velocities around 4.3-4.4 km s −1 . This low-velocity zone in the southern Aegean sea can be associated with the high temperatures and the presence of significant percentage partial melt in the mantle wedge of the southern Aegean subduction zone, in agreement with previous studies.

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