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Dipartimento di Scienze della Terra, Università di Genova, Italy
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- PublicationOpen AccessVLF prospecting: abservations about field experiments(1994-11)
; ; ; ;Bozzo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Lombardo, S.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Merlanti, F.; Dipartimento di Scienze della Terra, Università di Genova, Italy; ; 200 614 - PublicationOpen AccessGeophysical studies applied to near-surface karst structures: the dolines(1996-01)
; ; ; ;Bozzo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Lombardo, S.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Merlanti, F.; Dipartimento di Scienze della Terra, Università di Genova, Italy; ; The formation of dolines is a very common near-surface karst phenomenon which is widespread and evident throughout most of Italy. In this study different geophysical methods have been applied to doline-like structures in the volcaniclastic section of the Alps in order to define their main morpho-structural characteristics. An integrated analysis of the geophysical data was also carried out to ascertain the quality and the resolution obtained through these geophysical methods and more in general, to evaluate their applicability to areas displaying features which are similar to those currently investigated. The fundamental differences found in different dolines are related to the geometries of the contact between the sublayer and the infill and to the mineralogy of the latter. From a geophysical standpoint the contact represents a discontinuity between materials characterized by different geophysical properties, whereas the infill shows properties which vary according to their composition and texture.208 420 - PublicationRestrictedMapping the Moho of the Western Alps by wide-angle reflection seismics(1989)
; ; ; ; ; ; ; ; ; ;Hirn, A.; Institut de Physique du Globe, Parigi ;Nadir, S.; Institut de Physique du Globe, Parigi ;Thouvenot, F.; Observatoire de Grenoble ;Nicolich, R.; Università di Trieste ;Pellis, G.; Università di Trieste ;Scarascia, S.; Istituto di Geofisica della Litosfera, CNR ;Tabacco, I.; Istituto di Geofisica della Litosfera, CNR ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Merlanti, F.; Università di Genova; ; ; ; ; ; ; ; In the text253 29 - PublicationOpen AccessComparison of inversion methods in seismic tomography: application to tectonic structures in Northwestern Italy(1994-04)
; ; ; ; ; ;Maggio, F.; CRS4, Cagliari, Italy ;Malfanti, F.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Bertero, M.; Dipartimento di Fisica, Università di Genova and INFN, Genova, Italy ;Cattaneo, M.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Eva, C.; Dipartimento di Scienze della Terra, Università di Genova, Italy; ; ; ; In this paper we apply various inversion methods to a set of teleseismic data collected by a network operating along the Ligurian Belt in the transition region between Alps and Apennines. In particular, we consider the regularization method, the truncated singular value decomposition, the Landweber method (with the Related Simultaneous Iterative Reconstruction Technique) and the conjugate gradient method. All the methods provide rather similar velocity models which are well approximated by that provided by back-projection (used with an appropriate normalization constant). A drawback of these models seems to be the large discrepancy (of the order of 40%) between the observed time residuals and those computed from the model itself. However, for each station of the network, the azimuth dependence of the computed time residuals reproduces rather well the observed one so that it is believable that the most significant information contained in the data has been expIoited. The computed velocity models indicate strong heterogeneities in the first 200 km below the Apennines.159 296 - PublicationOpen AccessModelling of karst structures by geophysical methods. An example: the doline of S. Pietro dei Monti (Western Liguria)(1998-08)
; ; ; ; ; ;Armadillo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Massa, F.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Caneva, G.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Gambetta, M.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Bozzo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy; ; ; ; Integrated geophysical investigations of karst structures were carried out in Liguria and Piedmont (NW Italy); this paper refers to the S. Pietro dei Monti doline, in the karst area of Mt. Carmo (Savona). The techniques used in the integrated study were magnetics, electromagnetics and seismic refraction. The target was to identify, without drilling, the nature of the doline, for example if it is of dissolution or collapse type. A preliminary susceptibility sampling of the outcrop and topsoil and the diffuse fractures with a probable water seepage suggested magnetics and VLF electromagnetics. Such methods applied in an area with an extremely low cultural noise allowed modelling of the buried structure of the doline.261 470 - PublicationOpen AccessSome considerations on the use of the geoelectric «square» array(1996-01)
; ; ;Merlanti, F.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Pavan, M.; Dipartimento di Scienze della Terra, Università di Genova, Italy; The «square array» is what we may consider to be an unconventional geoelectric configuration since it is not widely used and therefore there are few examples of practical application. The purpose of this research was to verify the operating effectiveness of this configuration in terms of profile and sounding, and the significance of the set of possible measurements and derived parameters. This was also obtained by comparing the relative measurements with the most common linear arrays (Wenner, Schlumberger, tripotential). The experiment was carried out in two different zones. In the first area, corresponding to the archaeological site of Marzabotto (Bologna), the target was represented by wall remnants inserted in a substantially homogeneous medium, from an electrical point of view, and at depths that are less than those of the dimensions of the device used. At the second site, located in the valley of Landrazza (Savona), the situation was very different, with a valley section on a calcareous bedrock filled with poorly classified residual sediments. An overall analysis of the results showed that the square technique is more exhaustive than the classical linear arrangements when performing soundings. Instead, with regard to profile development, it is not as preferred since it involves a greater amount of work without generating improved information. From analysis of the experimental results, considerable doubts arose about the meaning and the use of the anisotropy coefficients and the error term as defined theoretically. These parameters turned out to be of little use with regard to the characterization of the ground anisotropy and for checking the reliability of the measurements.156 1018 - PublicationOpen AccessA magnetovariational study in Central Italy: Standard techniques(1994-11)
; ; ; ; ; ;Bozzo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Caneva, G.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Elena, A.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Gambetta, M.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Zunino, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy; ; ; ; magnetovariational study was performed in Central Italy, with an array of magnetometers located at Radicondoli (SI), Radda in Chianti (SI), Roccalbegna (GR), Città di Castello (PG) and Pennabilli (PS) from February to May 1992. Geomagnetic transfer functions in the frequency domain were calculated using the standard least squares tecnique. The induction arrows for the periods T= 32 min and T= 128 min, the Hypothetical Event (HE) maps and two IZ/HI pseudosections across the array, show the magnetovariational effect of the upper mantle anomaly in the Tuscan-Tyrrhenian area and the contrast between different crustal types.202 150 - PublicationOpen AccessTechnical procedures for aeromagnetic surveys in Antarctica during the Italian expeditions (1988-1992)(1994-11)
; ; ; ; ; ; ; ; ;Bozzo, E.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Colla, A.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Caneva, G.; Dipartimento di Scienze della Terra, Università di Genova, Italy ;Meloni, A.; Istituto Nazionale di Geofisica, Roma, Italy ;Caramelli, A.; Istituto Nazionale di Geofisica, Roma, Italy ;Romeo, G.; Istituto Nazionale di Geofisica, Roma, Italy ;Damaske, D.; Bundesanstalt fur Geowissenschaften und Rohstoffe, Hannover, Germany ;Moeller, D.; Bundesanstalt fur Geowissenschaften und Rohstoffe, Hannover, Germany; ; ; ; ; ; ; For most of Antarctica, the geophysical data now available are those of aeromagnetic surveys performed there from 1950 to 1960. Until 1984, the inaccurate positioning and insufficient monitoring of geomagnetic time variations allowed the investigation of the geomagnetic residual field only along profiles. The Ganovex IV aeromagnetic survey, performed by BGR-USGS over the Ross Sea and the Northern Victoria Land, and the geophysical investigations of BAS on the Southern Antarctic peninsula and the Ronne ice shelf region corresponds to the recent advancement of these techniques in Antarctica. The first experiments of aeromagnetic measurements, during the Italian expeditions in Antarctica were made during the 1988-1989 field season. Some geomagnetic helicopter borne profiles were accomplished with a Proton Precession Magnetometer (PPM) in the Terra Nova Bay-Gerlache Inlet area. In the 1989-1990 ItaliAntartide expedition some profiles were flown over the suture between the Wilson and Bower terranes, in Northern Victoria Land. During the 1991-1992 expedition, in cooperation with researchers of BGR (Bundesanstalt fur Geowissenschaften und Rohstoffe) of Hannover, the GITARA I (German ITalian Aeromagnetic Rescarch Antarctica) program, as part of the LIRA (Litospheric Investigation in the Ross Sea Area) project, was carried out. The investigated area lies between the latitudes 74°18' S and 75°18' S and the longitudes 160°30' E and 164°30'E and it corresponds to a portion of the North Victoria Land, located between the Eisenhower Range and the, DrygaIski Ice Tongue. The survey was made with a Cesium vapour magnetometer. The positioning system was of the “Range-Range” type, it consisted of three transmitters (beacons), installed inside the investigated area and located with GPS measurements. The line spacing was 4.4 km, with tie lines every 22 km. The survey covered an area of 6500 km2 . Four PPM base stations for the determination of the time variation corrections were installed. The aeromagnetic anomalies wilI allow the comparison with the ground geomagnetic surveys performed during the previous Antarctic expeditions, also in connection with the aeromagnetic maps of Ganovex IV, located at the northern and eastern boundaries of the GITARA area.237 142 - PublicationOpen AccessGeomagnetic survey of Italy at 1979.0 Repeat station network and magnetic maps(1994)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;A national network of 106 repeat stations for total field F, horizontal component H, vertical component Z and declination D has been undertaken in the frame of the 'Progetto Finalizzato Geodinamica' of the Consiglio Nazionale delle Ricerche. From the observed magnetic elements the repeat station values were referred to 1979.0 and five normal fields in the form of a 2nd order polynomial in latitude and longitude were computed: GDN for the whole Italian area, GDN-N for the northern Italy, GDN_C for central Italy, GDN-S for the southern Italy and GDN-Sn for Sardinia. From comparisons made on F between GDN and two planetary reference fields it has concluded that for total field the polynomial form can be well considered as representative of the main field in the Italian area. A 2nd order network of 2500 stations for F, Z, H, has been undertaken to produce geomagnetic maps of Italy. An anomaly map for F referred to the GDN normal field has been drawn. The main features of anomalies configuration are described.168 63 - PublicationRestrictedA new picture of the Moho under the western Alps(1989-01-19)
; ; ; ; ; ; ; ; ; ;Hirn, A.; Institut de Physique du Globe, Paris ;Nadir, S.; Institut de Physique du Globe, Paris ;Thouvenot, F.; Observatoire de Grenoble, IRIGM ;Nicolich, R.; Università di Trieste ;Pellis, G.; Università di Trieste ;Scarascia, S.; Istituto di Geofisica della Litosfera, CNR ;Tabacco, I.; Istituto di Geofisica della Litosfera, CNR ;Castellano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Merlanti, F.; Università di Genova; ; ; ; ; ; ; ; In the text215 43