there are some structures, mesolapine in origin and restructured in neoalpine phases: the Mt. Ciaurlec line, the Mt. Pala line, the Cuel dal Meloc line and the Mt. Bernadia line. Between the Arcola area and Soverzene (Veneto), a S-dipping backthrust of Barcis-Staro Selo constitutes the Val Ferron line. The area is the site of intense seismic activity. Oxygen isotopes indicate that the stud- ied aquifers are feeded by meteoric precipitations of different geographic provenance and exclude an hydraulic continuity among the reservoirs. Strontium isotopes also support the hypothesis of dis- tinct hydrological circuits and indicate that waters are in equilibrium with gypsum and limestone triassic deposits of the Raibl Formation, with a negligible contribution of a component represented by low-salinity waters circulating in the upper horizons, possibly originated by the direct infiltra- tion of rainwater. Strontium isotopes also indicate that in some cases these waters are probably interested by the dissolution of diagenetic mineral assemblages and the breakdown of silicate phas- es. Waters are out of thermodynamic equilibrium with evaporite gypsum and anhydrite, despite iso- topes indicate a prolonged water-rock interaction. The observed undersaturation in sulphate miner- als seems not to be attributable to SO 4 2- loss in reducing environment or to saturation and precipita- tion of sulfide minerals, and could reflect the record of thermal effects due to the decreasing of sol- ubility of these minerals as increasing temperature. The gypsum and anhydrite undersaturation is hence tentatively interpreted as pathfinder of transient heat flow anomalies at the depth of burial. Heat fluxes could have been caused by frictions during fault motions and slidings in the past, now observed with a delay which is dependent by the time required by waters to reach the surface. The lack of a present-day high temperature at the outlet could be explained by water-rock interactions in water-dominated systems, and by the relatively high flow rate as expected for fluids migrating along fault systems. Equilibrating the Ca 2+ and SO 4 2- activities we obtain last equilibrium tempera- tures of the order of 200 °C. The information here provided may be used to start up a long-term geo- chemical monitoring of this seismically active area able to detect the modifications occurring to the circulating fluids to gain a better insight on the relationships between the fluids’ geochemistry and the activity of the local seismogenic faults. PALEOTSUNAMI EVIDENCE IN THE AUGUSTA BAY (EASTERN SICILY, ITALY) A. Smedile 1 , P.M. De Martini 1 , M.S. Barbano 2 , D. Pantosti 1 , F. Gerardi 2 , P. Del Carlo 1 , L. Bellucci 3 , L. Gasperini 3 , L. Sagnotti 1 , A. Polonia 3 , C. Pirrotta 2 , P. Guarnieri 2 , M. Cosentino 2 1 Istituto Nazionale di Geofisica e Vulcanologia, Italia 2 Dipartimento di Scienze Geologiche, Università di Catania, Italia 3 Istituto di Scienze Marine, CNR, Italia The knowledge of location and timing of events of inundation related to tsunami of the past is particularly relevant for civil protection purposes, in particular for the development of tsunami sce- narios and time-dependent probabilistic tsunami hazard models. Evidence for the occurrence of tsunami of the past can be derived from the recognition of tsunami deposits as well as from other signatures left in the coastal landscape, environment, and sedimentary structures. Studies on this subject have been only developed sporadically in the Mediterranean and started to draw more attention only after the disastrous Sumatra tsunami occurred in 2004. Sites where to develop these studies should contain favorable conditions for formation, preservation and recognition of tsunami deposits or signatures. The Augusta Bay in Eastern Sicily appeared to potentially satisfy these requisites being a low coastal area, with local coastal lowlands or lagoons, and relevant offshore stratigraphy. Moreover, the area was repeatedly hit by tsunami inundations related to large historical earthquakes (CPTI Working Group, 2004) and information about hit localities, inundated areas and run-up distribution are available from contemporary reports. 181 GNGTS 2008 SESSIONE 2.1