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Dipartimento di Geologia, Paleontologia e Geofisica, Universitá di Padova, Italy
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- PublicationRestrictedA structural and geophysical approach to the study of fractured aquifers in the Scansano-Magliano in Toscana Ridge, southern Tuscany, Italy(2009-07)
; ; ; ; ; ; ; ; ; ;Francese, R.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy ;Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Bistacchi, A.; Dipartimento di Geologia e Geotecnologia, Università di Milano Bicocca, Milano, Italy ;Morelli, G.; Geostudi Astier S.r.l., Livorno, Italy ;Pasquarè, G.; Dipartimento di Geologia, Università di Milano, Milano, Italy ;Praticelli, N.; Dipartimento di Geoscienze, Università di Padova, Padova, Italy ;Robain, H.; Institute de Recherche pour le Développement, Bondy Cedex, France ;Wardell, N.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy ;Zaja, A.; Dipartimento di Geoscienze, Università di Padova, Padova, Italy; ; ; ; ; ; ; ; Fresh water availability has recently become a serious concern in the Italian Apennines, as various activities rely on a predictable supply. Along the ridge between Scansano and Magliano in Toscana, in southern Tuscany, the situation is further complicated by contamination of the nearby alluvial aquifers. Aquifers locally consist of thin fractured reservoirs, generally within low-permeability formations, and it can be difficult to plan the exploitation of resources based on conventional techniques. An integrated study based on geological data investigated the link between tectonics and groundwater circulation, to better define the hydrological model. After the regional identification of fault and fracture patterns, a major structure was investigated in detail to accurately map its spatial position and to understand the geometry and properties of the associated aquifer and assess its exploitation potential. The subsurface around the fault zone was clearly imaged using ground probing radar, two-dimensional and three-dimensional resistivity tomography, and three-dimensional shallow seismic surveys. The vertical and horizontal contacts between the different geological units of the Ligurian and Tuscan series were resolved with a high degree of spatial accuracy. Three-dimensional high-resolution geophysical imaging proved to be a very effective means of characterising small-scale fractured reservoirs.218 23 - PublicationOpen AccessNew magnetotelluric soundings in the Mt. Somma-Vesuvius volcanic complex: preliminary results(2000-04)
; ; ; ;Manzella, A.; Istituto Internazionale per le Ricerche Geotermiche, CNR, Pisa, Italy ;Volpi, G.; Istituto Internazionale per le Ricerche Geotermiche, CNR, Pisa, Italy ;Zaja, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Università di Padova, Italy; ; During 1997 ten magnetotelluric (MT) soundings were recorded in single-site mode above the Mt. Somma-Vesuvius volcanic area. A first campaign of MT measurements was carried out, during spring, by the researchers of the University of Padua with their MSPM acquisition system. During autumn, the researchers of the International Institute of Geothermal Research (CNR Pisa) with their Phoenix equipment performed a second campaign. A teach site, the horizontal components of the electrical and magnetic fields were recorded in the frequency band between 300-0.003 Hz. The MSPM system could record signals up to the frequency of 800 Hz. Data were recorded at one common site with both the different equipments to verify the compatibility of the two different acquisition systems. The soundings over the area of the volcano's caldera show a continuous morphology of the apparent resistivity and phase curves with small error bars: it means a good correlation between the orthogonal electrical and magnetic fields. The quality of data decreases going further from the caldera and approaching the sources of electromagnetic incoherent noise such as villages, antennas and repeaters. After a very accurate data analysis, the apparent resistivity and phase curves were interpreted with a 1D modelling instead a 2D one as it seems a more appropriate interpretative approach looking at the morphology of the curves and taking into account the 3D geological conditions of the area. The results show an extended conductive structure at a depth of 0.3-1.2 km. It could be connected with a change in the physico-chemical characteristics of the volcano-sedimentary cover (alteration paragenesis and possible hydrothermalism). A 3D MT forward modelling was then used to define the response MT curves for sites above this particular volcanic structure. This approach seems to be very interesting in view of specific interpretative targets, such as dimension and position of the magma chamber, when planning future MT surveys.141 526 - PublicationOpen AccessMagnetotelluric investigations of the seismically active region of Northwest Bohemia: preliminary results(1999-02)
; ; ; ; ; ; ; ; ;Di Mauro, D.; Istituto Nazionale di Geofisica, Roma, Italy ;Volpi, G.; Istituto Internazionale per le Ricerche Geotermiche, Pisa, Italy ;Manzella, A.; Istituto Internazionale per le Ricerche Geotermiche, Pisa, Italy ;Zaja, A.; Università di Padova, Italy ;Praticelli, N.; Università di Padova, Italy ;Cerv, V.; Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic ;Pek, J.; Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic ;De Santis, A.; Istituto Nazionale di Geofisica, Roma, Italy; ; ; ; ; ; ; During 1997, within the framework of an Italian-funded scientific cooperation between Italy and the Czech Republic, a series of magnetotelluric (MT) soundings was carried out in the region of Northwest Bohemia (Czech Republic). This is one of the most seismically active areas in Central Europe, where micro-earthquake swarms frequently occur during the apparently quiescent intervals between large macro-seismic swarms. Fifteen MT stations were installed in an area of about 15 ´ 20 km2 where 80% of the seismicity of the entire region has been recorded since 1986. The area showed a high electromagnetic noise, possibly of high cultural origin from the nearby industrial zone of the Sokolov basin, which affected both the electric and the magnetic signals. The final data, carefully selected, were modeled by 2D and 3D techniques. The results show an extensive conductive structure in the depth range from 0.5 to 3 km. This structure could be connected with the locally buried granitic massif in the inhomogeneous metamorphic basement, probably accompanied by fracturation, thermo-metamorphism or paleofluids. Moreover, the presence of a conductive anomaly in the northern part of the investigated region could be linked to a lithological change in the metamorphic rocks (prevalence of phyllites over mica schists), which would even increase the effect of the granite.197 238 - PublicationOpen AccessElectrical features of deep structures of Southern Tuscany (Italy)(1998-08)
; ; ; ; ; ;Fiordelisi, A.; ENEL-VDTG, Pisa, Italy ;Mackie, R.; Geosystem s.r.l., San Francisco, U.S.A. ;Manzella, A.; CNR, Istituto Internazionale per le Ricerche Geotermiche, Pisa, Italy ;Watts, D.; Geosystem s.r.l., Milano, Italy ;Zaja, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Universitá di Padova, Italy; ; ; ; Over the last six years, magnetotelluric data were acquired at 86 sites covering much of Southern Tuscany. Twenty-four of these sites were acquired in single-site or local-reference mode, whereas 62 were aquired in very-remote-reference mode, with a remote site located on Capraia Island í 40 km from the cost í where the cultural noise is very low. The data modelling showed that Southern Tuscany is characterized by a fairly uniform middle-lower crust that has a resistivity of a few thousand W ·m below 10 km. At shallower depths in the crust, the resistivity is closer to values around 500 W ·m. This uniformity is interrupted only below the Larderello and Mt. Amiata geothermal fields where deep conductive bodies are believed to exist. A general anomalous condition can hence be depicted for this region, with low resistivity values typical of those in tectonically active areas as opposed to more resistive values typical in continental areas. These data and those from other geophysical techniques suggest that these conductive zones may be associated with hot material coming from deeper sources below the geothermal areas.146 359 - PublicationOpen AccessMagnetotelluric and DC electrical soundings in the Po plain (Veneto region)(1998-08)
; ; ; ;Alfano, L.; Dipartimento di Scienze della Terra, Sezione di Geofisica, Universitá di Milano, Italy ;Giudici, M.; Dipartimento di Scienze della Terra, Sezione di Geofisica, Universitá di Milano, Italy ;Zaja, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Universitá di Padova, Italy; ; Eleven MT soundings and two dipole-dipole electrical soundings were carried out in the area of the Po plain south of the town of Padua. MT soundings were performed in the frequency band from 100 to 1/64 Hz; DC soundings were achieved, respectively, with a 2000 and 4000 m length of the array. The electrical interpretative models show a predominant monoclinalic tectonic behaviour with an evident deepening of the resistive basement to ward NE. The joint use of the two electrical techniques defined the geological and structural setting up to a depth of 2 km in a highly conductive area.127 318 - PublicationOpen AccessIntegrated geoelectrical and magnetotelluric exploration at Gran Sasso d'Italia range (Central Apennines)(1998-08)
; ; ; ;Alfano, L.; Dipartimento di Scienze della Terra, Sezione di Geofisica, Universitá di Milano, Italy ;Giudici, M.; Dipartimento di Scienze della Terra, Sezione di Geofisica, Universitá di Milano, Italy ;Zaja, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Universitá di Padova, Italy; ; We carried out three electrical soundings, with continuous polar dipole-dipole array, and three magnetotelluric stations at Gran Sasso d'Italia, in the area of Campo Imperatore. Geoelectrical data show the existence of a resistive background with exceptionally high values of resistivity (greater than 25000 Ω • m) at a depth of about 250 m. The magnetotelluric data were used to constrain the thickness of this resistive layer, below which we find an intermediate conductive structure and a deeper resistive background. The geological interpretation of this result is still open to discussion, but we can exclude that the shallow resistive layer consists of Cretaceous limestones, since their resistivity has been estimated to be about 5000 Ω • m.140 147 - PublicationOpen AccessMagnetotelluric and deep geomagnetic induction data in the Bohemian Massif(1997-03)
; ; ; ; ; ;Cerv, V.; Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic ;Pek, J.; Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic ;Praus, O.; Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic ;Zaja, A.; Dipartimento di Geologia, Paleontologia e Geofisica, Università di Padova, Italy ;Manzella, A.; Istituto Internazionale di Ricerche Geotermiche, C.N.R., Pisa, Italy; ; ; ; Manifestations of the increased tectonic activity (seismic activity, remnants of Tertiary volcanism and riftogenesis) in the Bohemian Massif are bound to geologically extremely complicated regions with a system of discordant structures and a mosaic of fault zones. The presented results concern the deep geoelectrical features of the tectonic transition between the Saxothuringian and Moldanubian tectonoblocks on the territory of West Bohemia, in close vicinity to the German deep drilling experiment KTB (Kontinentale Tiefbohrung der BRD). Three first-order tectonic lines demarcate the region under study í the Litomerice deep fault to the north, the West Bohemian deep fault zone to the east, and the Central Bohemian fault to the south. As a whole, the region involved is characterized by a regionally increased seismic activity with the most active zone just beyond the northern end-point of the profile investigated. The contribution can be considered an example of possible interpretation of MT/MV/AMT data in geologically extremely complicated conditions with evidently discordant structures affecting the geoelectrical data.146 170