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18 pages, 9 figures, supporting information https://doi.org/10.1111/bre.12211, The structural complexity of back‐arc basins is related to the evolution of the associated subduction system. Here, we present an integrated geophysical and geological study that constrains the 3D spatial variability of magmatic activity along the Tyrrhenian back‐arc basin. We use wide‐angle seismic and gravity data, acquired in 2010 within the MEDOC experiment along a ~300 km‐long NW‐SE transect that extends from SE Sardinia Island to the NW Sicily continental margin, across the Cornaglia Terrace. The geophysical transect is coincident with a seismic reflection line from the Italian CROP experiment that we have re‐processed. The geophysical results, together with available basement dredges, support a basement along the profile fundamentally composed of continental‐type rocks, locally affected by subduction‐related magmatism. The continental nature of this region contrasts with the nature of the basement inferred along two geophysical cross‐sections located to the north of the Cornaglia Terrace in which seismic velocity of the lower crust supports significant magmatic crustal accretion. The comparison of these three cross‐sections supports that the highest magmatic activity occurred in the central and most extended region of the basin, whereas it was less important in the North and practically nonexistent in the South. These observations indicate abrupt variations of magmatism during the basin formation. As in other back‐arcs, the temperature, water content and composition of the mantle might have played an important role in such variation, but they fail to explain the abruptness of it. We propose that the interaction of the overriding continental lithospheres of Adria and Africa with the Apenninic‐Calabrian subduction system caused changes in slab rollback and trench retreat dynamics, which in turn resulted in variations of back‐arc stretching and magmatism. Based on our observations, we suggest that the Cornaglia Terrace formation process might share some similarities with the formation of oceanic crust in the Red Sea, We thank the teams involved in the MEDOC project and the Complementary Action OSMART, which has been funded by the former Spanish Ministry of Science and Education, with reference CTM2007-66179/C02-01/MAR and CTM2007-66179-C02-02/MAR, and CTM 2009-07772-E/MAR respectively. The German Science Foundation (DFG grant GR 1964/14-1) supported I. Grevemeyer. This work was also supported by project CO-DOS funded by Repsol. […]M. Prada and M. G. Vendrell work were funded by the Spanish CSIC Jae-PreDoc and Spanish Ministry of Science and Education FPI grants system respectively

European Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 page, The Tyrrhenian back-arc basin formed as a result of the migration of subduction fronts towards the East and Southeast during the Neogene time. The complex evolution of this subduction system caused differences concerning the degree of back-arc extension from North to South; while rifting affected the northern region, continental break-up occurred in the central and southern regions. Recent results obtained from integration of geological and modern geophysical data revealed the presence of a magmatically-modified crust beneath the Cornaglia and Campania Terraces followed by mantle exhumation beneath the Magnaghi and Vavilov basins, implying abrupt variations of magmatic crustal accretion in few kilometres. Here we present more evidences of this heterogeneous magmatic activity by analysing the crustal and uppermost mantle structure beneath the Cornaglia Terrace along three geophyisical cross-sections of the basin. Crustal structure and Moho geometry along each transect are constrained by a 2D P-wave velocity model obtained by joint refraction and reflection travel-time tomography, a coincident Multichannel Seismic image and the corresponding P-wave velocity-derived gravity modelling. From North to South of the Cornaglia Terrace, mean lower crustal velocity increases from the northern region (6.4-6.7 km/s) to the central part (6.8-6.9 km/s), and drastically decreases southwards (5.9-6.1 km/s). Along-axis lower crustal velocity variations are in accordance with variations in the degree of crustal extension. While in the northern and southern regions the crust thins up to 7-8 km thick, in the central part extension leads to crustal break up and later mantle exhumation. Based on these results and on an exhaustive velocity analysis, we suggest that these variations reveal a different degree of magmatism along the terrace axis. The highest magmatic activity is focused beneath the central and most extended region of the terrace, whereas it is less important in the northern part, and practically inexistent beneath the southernmost region. The outcome of this study underpins the relation between magmatism and extension in this region of the Central Tyrrhenian basin, and evidences relevant differences of strain during the basin formation

16TH SEISMIX International Symposium on Multi-scale Seismic Imaging of the Earth's crust and Upper Mantle, 12-17 October 2014, Castelldefels, Barcelona.-- 1 page, The Tyrrhenian back-arc basin formed as a result of the migration of subduction fronts towards the east and southeast during the Neogene. The complex evolution of this subduction system caused differences concerning the degree of back-arc extension from north to south: while the northern region suffered a moderate amount of rifting, full continental break up occurred in the central and southern regions. In 2010, the MEDOC experiment was carried out with the collaboration of the Spanish B/O Sarimiento de Gamboa, the Italian R/V Urania, and several land teams to investigate the crustal structure of the basin and provide new insights on the formation processes of rifted continental margins. During the survey, multichannel seismic (MCS) and wide-angle seismic (WAS) data were acquired across the Tyrrhenian basin along five coincident transects, together with gravimetric, bathymetric, and hydrographic data. Here we present WAS, MCS, and gravity MEDOC data acquired along two of these transects: E-F (~400 km-long) and G-H (~450 km-long), both crossing the central basin from Sardinia to Campania. WAS data along transect G-H were recorded by 5 Land stations (LS), and 26 Ocean Bottom Seismometers and Hydrophones (OBS/H). Similarly, line E-F WAS data were recorded by 5 LSs and 28 OBS/H. The coincident MCS data along these two lines were acquired using a 276-channel, 3450 m-long streamer. Travel-times of first arrivals and Moho reflections were manually tracked from the OBS/H recordings and modelled using the tomo2d joint refraction and reflection travel-time inversion method to obtain the corresponding 2D P-wave velocity models. MCS data were processed to obtain two post-stack time migrated profiles. Integration of these results together with a rigorous velocity uncertainty analysis and a Vp-derived density modelling reveal that regions previously interpreted as extended continental crust present velocities and densities consistent with those expected for magmatic rocks, whereas basement properties in other regions previously interpreted as oceanic crust are better explained by exhumed mantle rocks

European Geosciences Union General Assembly 2014 (EGU2014), 27 april - 2 may 2014, Vienna, Austria.-- 1 page, The Tyrrhenian Sea constitutes a young, well-preserved example of Mediterranean back-arc oceanic basin. It opened mainly between Tortonian and mid-Pliocene as a response to the E-SE migration of the ApenninesCalabrian subduction system. We present a new interpretation of the crustal affinity and tectonic structure of the central Tyrrhenian basin, which considerably differs from previous ones, from two coincident wide-angle and multi-channel seismic reflection profiles and gravity data acquired in the MEDOC-2010 survey. The basin displays three distinct basement domains with different petrological affinity based on their velocity and velocity-derived density structure. The first domain includes the continental crust of Sardinia and the conjugate Campania margin. In the Sardinia margin extension has thinned the crust from ~20 km under the coastline to ~13 km in ~60 km. Similarly, the Campania margin is also affected by strong extensional deformation. The basement in the second domain, under the Cornaglia Terrace and its conjugate Campania Terrace, appears to be oceanic in nature. It shows differences with respect to the reference young Atlantic oceanic crust while it agrees with that described in back-arc oceanic settings. The high velocity and velocity gradient and the lack of crust-mantle reflections in seismic records of the third domain, which encompasses the Magnaghi and Vavilov basins, indicate that the basement is fundamentally made of exhumed mantle rocks, in accordance with previous observations from hole 651 at Ocean Drilling Program Leg 107. Several large seamounts of the third domain (e.g. Vavilov) are underlain by 10-20-km-wide, relatively low velocity anomalies interpreted as younger magmatic bodies locally intruding the exhumed mantle. We interpret that these domains correspond to different phases of back-arc spreading controlled by the variations on the relative location of the spreading axis and the active volcanic arc due to the migration of the subduction system

21 pages, 12 figures, 1 table, Extension of the continental lithosphere leads to the formation of rift basins and ultimately may create passive continental margins. The mechanisms that operate during the early stage of crustal extension are still intensely debated. We present the results from coincident multichannel seismic and wide-angle seismic profiles that transect across the northern Tyrrhenian Sea Basin. The profiles cross the Corsica Basin (France) to the Latium Margin (Italy) where the early-rift stage of the basin is well preserved. We found two domains, each with a distinct tectonic style, heat flow and crustal thickness. One domain is the Corsica Basin in the west that formed before the main rift phase of the northern Tyrrhenian Sea opening (∼8-4 Ma). The second domain is rifted continental crust characterized by tilted blocks and half-graben structures in the central region and at the Latium Margin. These two domains are separated by a deep (∼10 km) sedimentary complex of the eastern portion of the Corsica Basin. Travel-time tomography of wide-angle seismic data reveals the crustal architecture and a subhorizontal 15-17 ± 1 km deep Moho discontinuity under the basin. To estimate the amount of horizontal extension we have identified the pre-, syn-, and post-tectonic sedimentary units and calculated the relative displacement of faults. We found that major faults initiated at angles of 45°-50° and that the rifted domain is horizontally stretched by a factor of β ∼ 1.3 (∼8-10 mm/a). The crust has been thinned from ∼24 to ∼17 km indicating a similar amount of extension (∼30%). The transect represents one of the best imaged early rifts and implies that the formation of crustal-scale detachments, or long-lived low-angle normal faults, is not a general feature that controls the rift initiation of continental crust. Other young rift basins, like the Gulf of Corinth, the Suez Rift or Lake Baikal, display features resembling the northern Tyrrhenian Basin, suggesting that half-graben formations and distributed homogeneous crustal thinning are a common feature during rift initiation. ©2013. American Geophysical Union. All Rights Reserved, Funding for data acquisition was provided by Spain (projects CTM2007-66179-C02-01/MAR and CTM2009–07772-E/MAR) and Italy which we gratefully acknowledge. [...] This work was funded by the Deutsche Forschungsgemeinschaft (DFG) under grant GR 1964/14-1

AAPG European Regional Conference & Exhibition. Exploring The Mediterranean: New Concepts In An Ancient Seaway, 8-10 April 2013, Barcelona, Spain

San Lucano Valley (Belluno, Italy) is included in the UNESCO System n.3: award of "World Heritage" area. The land use in the valley is not intensive and there has not been interference to the riparian zone, since the flood of 1966, during which the majority of the existing trees (conifer) were uprooted. After 1966, an exceptional riparian forests of Alnus incana and Fraxinus excelsior with some Mountain Maple and Spruce, took over. These forests are of high natural interest for the E. C.: (site BL28 from Natura 2000 network), and constantly under observation and carefully preserved. For these reasons, the lower Tegnas River has become an open-laboratory to study the stream and how it adjusts from past periods to recent morphodynamic events, and to verify the applicability of the methodology referred as Watershed Assessment of River Stability and Sediment Supply (Rosgen, 2006) in the morphological context of the Alps and in their hydroclimatic environment. The stream geomorphology shows the evidence of channel changes during over 50 years. Quaternary fluvial deposits, postglacial landslides and debris flows are filling the valley bottom with a 200m thick covering. The gravel of this flat area must be periodically quarried to ensure the hydraulic protection of the sideway road, but the newly rebuilt banks are quickly eroded due to the floods and the streambed becomes impracticable and unsuitable for spontaneous fish habitats and for forest growth. The monitoring of streams over time, modeling their geomorphologic trends, gives some contribution to understand the erosion-transport-deposition process in order to reset a more stable, long-lived, riverbed with natural solutions. This may be a useful approach in restoration plans, in order to make the riverbed renaturalization more stable and improving the accessibility to the riparian zone, without disregarding the preservation of the natural environment quality.

AGU Fall Meeting 3–7 December 2012, San Francisco, California, The Tyrrhenian basin has been formed by extension of overriding continental lithosphere driven by roll back of the Ionian slab across the mantle. The basin is not actively extending but the tectonic structure provides information of the processes that controlled rifting and formation of conjugate margins. The basin opened from west to east, with rifting stopping after progressively larger stretching factors from north to south. The northern region stopped opening at extension factors about 1.8. Towards the south extension continued until full crustal separation that produced first intense magmatism that subsequently was followed by mantle exhumation. The final structure displays two conjugate margins with structures that evolved from symmetric to asymmetric as extension rates increase and a complex tectonic structure in between. The basin provides a natural laboratory to investigate a full rift system with variable amounts of extension. We present observations from a two-ship wide-angle (WAS) and multichannel reflection seismic (MCS) experiment that took place in spring 2010. The experiment took place on two legs: The first leg with Spanish R/V Sarmiento de Gamboa and Italian R/V Urania collected five WAS profiles striking E-W across the entire basin recorded on ocean bottom seismic stations and land stations with a 4800 c.i. G-II gun array as source. The second leg with R/V Sarmiento de Gamboa collected 16 MCS profiles (about 1500 km) using a 3.75 km-long streamer and a 3100 c.i. G-II gun array as source. MCS profiles were shot coincident with WAS profiles. WAS – MCS transects were located in regions with different amount of extension the study the full structure including the two conjugate margins. Additional MCS lines were shot concentrated in the region where mantle exhumation has taken place. The seismic information is placed in a 3D context with the integration of the multibeam bathymetry that covers the entire basin. We present the interpretation of the tectonic structure from MCS images and bathymetry and the calibrated stratigraphy of the basin that gives information of timing, duration, and amount of the tectonic extension for the different transects. We compare those results with the final P-wave velocity models from the five WAS profiles that supply information on the nature of the crust. Each transect provides information of the relationships among extension rates, crustal thickness, nature of the crust, and style of deformation. This information allows to interpret mechanisms of deformation, to infer the importance of magmatism in the rifting process, and to interpret the changes leading of mantle exhumation. Furthermore, the data provide insight in the process of formation of the structure conjugated margins. © 2014 American Geophysical Union. All Rights Reserved

AGU Fall Meeting 3–7 December 2012, San Francisco, California

AGU Fall Meeting 3–7 December 2012, San Francisco, California, We use coincident wide-angle (WAS), multichannel seismic reflection (MCS) images and gravity data acquired with the MEDOC cruise in 2010 to characterize the crustal domains and tectonic structure across the Tyrrhenian basin. We present a ~450 km-long, E-W-trending transect, which crosses the entire basin, from Sardinia (40N), across Sardina basin, the Cornaglia Terrace and the deep Magnaghi and Vavilov basins, to the Campanian margin (Italy). The joint interpretation of the WAS model and time-migrated MCS profile give information to understand the rifting phases leading to continental break-up and mantle exhumation. The WAS data , recorded on 26 OBH/S (Ocean bottom hydrophones/ seismometers) and 5 land stations, were modelled to obtain a P-wave velocity model of the basin and the geometry of the crust-mantle boundary by joint refraction and reflection travel-time tomography. The statistical uncertainty of the model parameters has been estimated following a Monte Carlo-like approach. Subsequently, a velocity-derived density model using existing relationships for different rocks was used to infer the composition of domains that fit gravity data being consistent with the velocity model. The model display abrupt lateral heterogeneity, showing four crustal domains based on velocity gradients. From West to East, the first domain consist of a ~23 ±2 km-thick continental crust beneath Sardinia and its shelf, with a mean velocity of 6.5 ±0.3 km/s. Eastwards, the crust thins from 22 ±2 km to 12 ±1 km in ~140 km below the Sardinia basin. This second domain is interpreted as a highly extended continental crust, containing numerous faults imaged in the coincident MCS profile. The third domain, in the central part of the profile, includes basins under the deepest water depth, and is interpreted as floored by exhumed mantle. In this domain, no crust-mantle reflections are identified, neither in the WAS data nor in the MCS images. Here, the velocity increases rapidly from 2.6 ±0,1 km/s at the sea-floor to ~7.8 ±0,15 km/s at ~5 km below. The vertical velocity gradient is twice larger than typical for oceanic Layer 2, and consistent with that observed in regions of mantle exhumation like the West Iberian Margin. In this third domain, we find three conspicuous velocity anomalies located under large volcanic seamount, formed by Upper Pliocene and Middle Pleistocene extension-related magmatism of the Magnaghi seamount, D'Ancona Ridge and Vavilov seamount, respectively. In the Eastern segment of the profile, beneath the Campanian margin, there are well-defined crust-mantle reflections in both WAS data and MCS profile, displaying a progressive thickening of continental crust towards mainland. The velocity gradient in this fourth domain is similar to that of the highly extended continental crust of the second domain, which approximately corresponds to its conjugate margin. Based on these seismic observations we conclude that, in this part of the Tyrrhenian basin, extension occurred slowly enough to exhume mantle rocks without producing significant synchronous magmatism that generated well-defined oceanic crust

Parte prima 86° Congresso della Società Geologica Italiana Note brevi e riassunti, Arcavacata di Rende, 18-20 Settembre 2012.-- 2 pages, 1 figure, The Tyrrhenian basin has formed in a subduction setting context, by extension of the overriding continental lithosphere in a process fundamentally driven by the retreat of a Ionian slab across the mantle. The lack of important normal-fault seismicity across the northern half of the basin seems to indicate that extension fully stopped there. The preserved basin structure provides information of the time evolution of the processes involved in rifting. The basin rifting rates and amount of extension changes from north to south, with rifting stopping after progressively larger stretching factor towards the south. The northern region stopped opening after a relatively low extension factor. Towards the south extension increased up to full crustal separation that produced mantle exhumation and locally collocated large-scale volcanism. The final structure displays two conjugate margins with asymmetric structures. Thus, the basin provides a natural laboratory to investigate a full rift system, that displays variable amounts of extension

European Geosciences Union General Assembly 22-27 April 2012, Vienna, Austria.-- 1 page, Located between Italy, Corsica, Sardinia and Sicily the Tyrrhenian Sea is a Neogene back-arc basin formed by continental extension related to the southeastward rollback of the subducting Ionian oceanic plate. This basin is an ideal place to study the evolution of extension process. The basin structure displays different amount of extension along its length, from the low-extension episodes of continental rifting in the northern areas to break up and exhumation of the mantle in the deepest part of the basin. Here there also seems to be evidence of extension-associated volcanism. In order to study the nature of the crust and the 4D evolution of the Tyrrhenian basin, a survey to collect multichannel (MCS) and wide-angle seismic (WAS) data was carried out into the framework of the MEDOC project in 2010 with the coordination of 2 research vessels, the R/V Sarmiento de Gamboa and the R/V Urania. During the experiment a total of 17 MCS lines and 5 WAS lines were acquired, with 125 deployments of both Ocean Bottom Hydrophones and Seismometers (OBH/S) and simultaneous land recordings in Corsica, Sardinia and Italy. In this work we present modeling results along two WAS lines that cross the central and deepest area of the basin. The models, which are obtained by joint refraction and reflection travel-time tomography, unveil the seismic structure of the crust and uppermost mantle and the geometry of the Moho boundary. The data selected for the inversion are arrival times of phases refracted through the crust and upper mantle (Pg and Pn phases), and those reflected at the Moho boundary (PmP phases). A statistical uncertainty analysis has been also performed to account for the inverted model parameters uncertainty (velocity values and Moho geometry). The seismic structure of both models reveals a significant lateral variation of the velocity gradient that has allowed defining various different crustal domains. In the western side of the profiles, the models show a progressive transition between a 23 km-thick continental crust, and a thinned, and apparently magmatically-intruded crust with a well-defined Moho boundary. Thinning is more pronounced in the central, deepest part of the basin, where the abrupt thinning coincides with the absence of PmP reflections and, in turn, with that of a well-developed Moho boundary. In this area, the velocity model indicates that the basement is mainly made of exhumed upper mantle rocks such as those described in the ODP Leg 107 in 1990. Finally, in the central part of the basin where the exhumed mantle domain is larger we find three low-velocity anomalies attributed to the extension-related magmatism

European Geosciences Union General Assembly 22-27 April 2012, Vienna, Austria.-- 1 page, The Tyrrhenian basin has been created during the extension of continental lithosphere driven by the retreat of a Ionian slab across the mantle. The basin does not seem to be actively extending, but its preserved crustal structure provides information of the time evolution of the processes involved in rifting. The basin rifted from north to south, with rifting stopping after progressively larger stretching factor towards the south. The northern region stopped opening after a relatively low extension factor. Towards the south extension increased up to full crustal separation that produced mantle exhumation. The final structure displays two conjugate margins with asymmetric structures. Thus, the basin provides a natural laboratory to investigate a full rift system, that displays variable amounts of extension. We present observations from a two-ship seismic experiment that took place in spring 2010. The cruise took place on two legs. In the first leg, the Spanish R/V Sarmiento de Gamboa and the Italian R/V Urania collected five E-W trending wide-angle seismic (WAS) profiles across the entire basin using 17 Ocean Bottom Seismometers and 25 Ocean Bottom Hydrophones and a 4800 c.i. G-II gun array. The profiles were extended with land stations that recorded the marine shots. During a second leg the R/V Sarmiento de Gamboa collected 16 Multichannel Seismic Reflection (MCS) profiles using a 3.75 km-long streamer and a 3000 c.i. G-II gun array. MCS profiles were acquired coincident with the WAS profiles, and a number of additional lines concentrated in the central region of the basin where mantle exhumation took place. The seismic profiles were located to cover regions of the basin that displays different amount of extension, and the coincident wide-angle and MCS transects cross the entire basin to image the two conjugate margins. In this presentation we compare observations from different transects mapping the structures produced at different extension factors. A comparison of the different transects permits to trade space (different transects mapping different extension factors) for time (different transects provide an evolutionary snapshot of the extension process). Each transect provides the tectonic structure, the geometry of sedimentary deposits, and P-wave seismic velocity distribution. This information allows to interpret the mechanisms of deformation, infer the importance and potential role of magmatism in the rifting process, and estimate the region of mantle exhumation, currently inferred from one drill site. The analysis of the data provides insight in the process of formation of asymmetry structure conjugated margins

European Geosciences Union General Assembly 2013, 7-12 April, Vienna, Austria, Extension in the continental lithosphere leads to the formation of rift basins or finally to passive continental margins where plates fully broke apart. The extensional processes at basins and passive margins are still not fully understood. One of the reasons is that the observed amount of crustal thinning is often much higher than the horizontal extension in the brittle upper crust that can be accounted by faulting. Moreover, conjugated margins are often observed to be asymmetric in tectonic style. Regarding these objective we present an analysis of two W-E striking multichannel- and wide-angle seismic sections from the Northern Tyrrhenian Sea. The new data were acquired onboard the Spanish R/V Sarmiento de Gamboa and Italian R/V Urania in spring 2010, within the framework of the MEDOC project. The lines cross the basin from the Corsica and Sardinia Margins towards the conjugated Latium and Campania Margins (Italy). The transects are divided in four zones distinguishable in tectonic style, velocity distribution, heat-flow and crustal thickness: 1) The deep sedimentary Corsica and Sardinia basins in the West which formed during Oligocene (~30 Ma) and reveal a fan-shaped sedimentary infill that is sealed by a Messinian erosional unconformity on top (~5-7 Ma). 2) Large rotated blocks bounding the deepest sub-basins along the entire transects and contain Messinian syn-tectonic sediments. 3) A zone of highly fractured continental crust broadens to the south and is indicated by a high number of faults and coincident with a velocity reduction. Furthermore, magmatic activity during Pliocene age in the southern line is evident in the southern line. 4) Flat summits at the Latium Margin indicate that this zone was above seal-level during rifting whereas the southern region was sub-sealevel. Faults cutting the seafloor indicate recent tectonic activity. To quantify the amount of horizontal extension we identified pre-, syn-, and post-tectonic sedimentary units in the northern line, calculated the relative extension factor by large faults as well as balancing the length of the pre-tectonic basement. The Messinian reflector can be well identified throughout both sections and is therefore an excellent time-marker within the syn-tectonic sequence. The syn-tectonic sequence is limited by a reflector of Pliocene age. The above lying Pleistocene to Quaternary sediment is undisturbed and identified as the post-tectonic sequence except for the eastern region to the South (CD-line). Tomography of first arrivals obtained from wideangle seismic data reveals the crustal architecture and thickness of 17 km ± 1 km along the northern profile. We found that the crust east of the Corsica Basin towards the Latium Margin is horizontally stretched by ~30 % and thinned vertically by the same amount (-factor=1.3). Along the MEDOC-CD line the crustal has thinned by a factor of 1.5 in the vicinity of the Sardinia Basin and thins to a maximum of 2.2 (11 km) towards the mainland of Italy. Whereas the northern region has apparently stretched symmetrically, the higher stretched southern transect builds a pair of asymmetric conjugated margins

This paper presents a signal processing procedure to perform refractor velocity analysis. The procedure enables one to obtain the seismic velocity from the refracted wavefield without the picking of refracted arrival times. Two processing procedures are derived, one starting from a seismic interferometric approach and another, from the conventional reciprocal method and generalized reciprocal method approaches. The theoretical equivalence of the two approaches is also demonstrated. The proposed processing procedure is applied to synthetic data in order to test the influence of some procedural parameters and its capability to reconstruct a known velocity model starting from refracted signals, without and with perturbations, in arrival times and noise; finally, it is applied to a field data set.

An organic organization and implementation of the available geothermal data in the southern Italian Regions (Campania, Calabria, Puglia and Sicily) useful to improve the exploratlon and exploitation of geothermal reservoirs, is the alm of the CNR project "Evaluation of Geothermal Potential in Convergence Regions" (VIGOR), financed by the Inter-Regional Operational Programme "Renewable Energy and Energy Conservation" POI 2007-2013. In the Mondragone area hydrothermal evidences has been known since roman time, and this area has been chosen to further improve geothermal knowledge through new geophysical and geologicaI exploration survey. From the geological point of view, the area is defined by an horst structure (Mt. Massico) elongate in NE-SW direction, characterized by a succession of Triassic-Cretaceous dolomitic Iimestone and Miocene terrigenous sediments. The Quaternary deposits are widespread in the adjacent plans, where the continental and marine sediments, interbedded with Roccamonfina and Campi Flegrei pyroclastic deposits, filling the Garigliano, to NW, and Volturno, to SE, graben, separated by the Mt Massico horst throught a NE-SW striking normal faults (Bergomi et al., 1969). Field and seismic data indicate the study area is interested by deep normaI NE-SW and N-S striking faults, although ESE-WNW to E-W strike-slip left-Iateral faults are also present (Billi et al., 1997; Bruno et al., 2000). Probably these structural pattern plays an important role for the Mt. Massico groundwater circolation, partially confining such structure from the less permeable deposits of plains, and allowing the groundwater to f10w primarily to the aquifer of the Garigliano plain (Allocca et al., 2005). At the southeastern edge of the massif four sulfur hot springs with temperatures between 22°C and 50°C emerge. In particular two hot springs, ("La Calda" and "Della Salute", up to 50°C and 29°C respectively) are located at the foothill of the Miocene terrigenous succession of Mt. Pizzuto, closely to the coast (Bergomi et al., 1969, Corniello, 1988). While the other two ("S. Giuseppe" and "Mt. Petrino solforosa" up to 22°C and 28°C respectively) are located at the foothill of the Mt. Petrino carbonatic structure (Trumpy & Manzella, 2009). According to some authors, the hot springs are fed by groundwater carbonate aquifer, where the water is heated and enriched of endogenous gas (CO2 H2S), rising along the extensive and deep tectonic discontinuity present, further testified by the morphological evidenced (sinkholes) found all along the southeastern edge of the Mt Massico (Del Prete et al., 2004). Moreover the different temperatures and degrees of mineralization of the four springs are interpreted as closely Iinked to the rising speed and water-rock contact time (Corniello, 1988; Allocca et al., 2005). A delimited area of 20 km2 south-east of Mt. Massico has been chosen to be studied by means of geological and geophysical surveys and deep drilling to provide analytical information useful to develop an hydrogeological 3D model that will allows the application of technologies for direct explotation of heat from geothermal source.