http://hdl.handle.net/2122/200 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/6035 Titolo: Insights into fluid circulation across the Pernicana Fault (Mt. Etna, Italy) and implications for flank instability<br/><br/>Autori: Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Tripaldi, S.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Piscitelli, S.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Balasco, M.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Magri, C.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Naudet, V.; Université Bordeaux 1, Geosciences Hydrosciences Material and Constructions, GHYMAC-EA 4134, Talence, F-33405, France; Rizzo, E.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy<br/><br/>Abstract: We conducted geophysical–geochemical measurements on a ∼2 kmN–S profile cutting across the PernicanaFault, one of the most active tectonic features on the NE flank of Mt. Etna. The profile passes from theunstable E flank of the volcano (to the south) to the stable N flank and significant fluctuations in electricalresistivity, self-potential, and soil gas emissions (CO2, Rn and Th) are found. The detailed multidisciplinaryanalysis reveals a complex interplay between the structural setting, uprising hydrothermal fluids, meteoricfluids percolating downwards, ground permeability, and surface topography. In particular, the recoveredfluid circulation model highlights that the southern sector is heavily fractured and faulted, allowing theformation of convective hydrothermal cells. Although the existence of a hydrothermal system in a volcanicarea does not surprise, these results have great implications in terms of flank dynamics at Mt. Etna. Indeed,the hydrothermal activity, interacting with the Pernicana Fault activity, could enhance the flank instability.Our approach should be further extended along the full extent of the boundary between the stable andunstable sectors of Etna for a better evaluation of the geohazard in this active tectonic area. Thu, 01 Apr 2010 00:00:00 GMT http://hdl.handle.net/2122/5538 Titolo: "Preface", special issue on "Geomagnetic Measurements in Remote Regions"<br/><br/>Autori: De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Arora, B.; Wadia Institute of Himalayan Geology, Dehradun, India; McCreadie, H.; Ludwig-Maximilians-Universität, Munich, Germany<br/><br/>Abstract: N. A.<br/><br/>Descrizione: Gli autori sono anche gli Editor di questonumero speciale Sun, 01 Feb 2009 00:00:00 GMT http://hdl.handle.net/2122/5369 Titolo: Imaging 2D structures by the CSAMT method: application to the Pantano di S. Gregorio Magno faulted basin (Southern Italy)<br/><br/>Autori: Troiano, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Di Giuseppe, M. G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Petrillo, Z.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Patella, D.; Department of Physical Sciences, University Federico II, Naples, Italy<br/><br/>Abstract: A controlled source audiofrequency magnetotelluric (CSAMT) survey has been undertaken inthe Pantano di San Gregorio Magno faulted basin, an earthquake prone area of SouthernApennines in Italy. A dataset from 11 soundings, distributed along a nearly N-S 780 m longprofile, was acquired in the basin’s easternmost area, where the fewest data are available as tothe faulting shallow features. A preliminary skew analysis allowed a prevailing 2D nature ofthe dataset to be ascertained. Then, using a single-site multi-frequency approach, Dantzig’ssimplex algorithm was introduced for the first time to estimate the CSAMT decompositionparameters. The simplex algorithm, freely available online, proved to be fast and efficient. Bythis approach, the TM and TE mode field diagrams were obtained and a N35!W ± 10! 2Dstrike mean direction was estimated along the profile, in substantial agreement with the faulttraces within the basin. A 2D inversion of the apparent resistivity and phase curves at sevenalmost noise-free sites distributed along the central portion of the profile was finallyelaborated, reinforced by a sensitivity analysis, which allowed the best resolved portion of themodel to be imaged from the first few meters of depth down to a mean depth of 300 m b.g.l.From the inverted section, the following features have been outlined: (i) a cover layer withresistivity in the range 3–30 ! m ascribed to the Quaternary lacustrine clayey deposits fillingthe basin, down to an average depth of about 35 m b.g.l., underlain by a structure withresistivity over 50 ! m up to about 600 ! m, ascribed to the Mesozoic carbonate bedrock;(ii) a system of two normal faults within the carbonate basement, extending down to themaximum best resolved depth of the order of 300 m b.g.l.; (iii) two wedge-shaped domainsseparating the opposite blocks of the faults with resistivity ranging between 30 ! m and 50 !m and horizontal extent of the order of some tens of metres, likely filled with lacustrinesediments and embedded fine gravels. Tue, 24 Mar 2009 00:00:00 GMT http://hdl.handle.net/2122/5337 Titolo: Harbour Sea-floor Clearance: “HD” High Definition Magnetic Survey Performance<br/><br/>Autori: Faggioni, O.; Istituto Nazionale di Geofisica e Vulcanologia; Soldani, M.; Istituto Nazionale di Geofisica e Vulcanologia; Leoncini, D.; Defence Geophysics Group; University of Genoa, DIBE, SEA Lab, Via All’Opera Pia 11a, 16145 Genova, Italy; Zunino, R.; Defence Geophysics Group; University of Genoa, DIBE, SEA Lab, Via All’Opera Pia 11a, 16145 Genova, Italy; Gastaldo, P.; Defence Geophysics Group; University of Genoa, DIBE, SEA Lab, Via All’Opera Pia 11a, 16145 Genova, Italy; Di Gennaro, E.; Italian Navy, Naval Logistic Inspectorate, Piazza della Marina 4, 00196 Roma, Italy; Lamberti, L. O.; Italian Navy, Istituto Idrografico della Marina, Passo dell’Osservatorio 4, 16134 Genova, Italy; Maggiani, P. V.; Italian Navy, COMFORDRAG, Viale Giovanni Amendola 1, 19122 La Spezia, Italy<br/><br/>Abstract: Seafloor clearance methods based on acoustic,direct-inspection, and single-sensor magnetic approaches suffer from limitations in controlling the target-sensor distance, and may prove ineffective when the small size or the dangerous nature of targets requires high accuracy in localization.Moreover, random magnetic variations over time bring about spatial decorrelation phenomena, and hinder the application ofdouble-sensor methods in noisy harbour environments.The new High Definition (HD) magnetic survey protocol tackles the measurement-distance problem in two ways: first, by varying the sensor depth dynamically, and secondly by backprojecting the measured field according to seafloor data and vertical incremental factors associated with the bandwidthcharacteristics of targets. The method to make up for timeinduced loss in spatial localization ability exploits the localbehaviour of a coherence function, which correlates local observations to a set of spatially-stabilized reference stations. Theconsequent normalization of measured magnetic signals allows one to assign the monitored areas with a specific level ofconfidence in the detection results, ranging from 100% (certainty) to 0% (random events).The principles of HD detection have been fully applied in the seafloor clearance of the firing test site located south of CapeTeulada (Sardinia, Italy), where very weak signal sources such as cartridge cases, mines, and small objects down to 1 Kg massvalues (lobster pots) have been successfully localized, even when covered by extensive colonies of Posidonia. Wed, 21 Oct 2009 00:00:00 GMT http://hdl.handle.net/2122/5320 Titolo: MAG: Magnetic Archaeo Geophysics<br/><br/>Autori: Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Gambetta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Curatori: Xavier Nieto; Centre d’Arqueologia Subaquàtica de Catalunya-Museu d’Arqueologia de Catalunya; Miguel Ángel Cau; Institució Catalana de Recerca i Estudis Avançats<br/><br/>Abstract: This note provides a synthetic overview of magnetic survey as applied to archaeology. The note gives a detailed section where the newest elaboration and interpretation techniques are shown. A brief introduction to the geomagnetic field and its time-dependent variations is also presented.A selection of further readings can be found in appendix. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5123 Titolo: Monitoring the mechanical stress of rocks through the electromagnetic emission produced by fracturing<br/><br/>Autori: Nardi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caputo, M.; Department of Physics, University of Rome ‘‘LaSapienza’’, Rome, Italy<br/><br/>Abstract: The present note shows that the rock mass under stress and strain generates an ELF and VLF emission (EME) associated to the fracturing phenomena. On uniaxial stress this emission show two different modes. A disorderly succession of clustering EM pulses (DIS) is associated with the acoustics emission of fracturing. It is always manifested, culminates with the rupture and begins just before the 50% of the time necessary to break the rock with an constant increasing stress. In some cases, this phenomenon is preceded by a more orderly and homogeneous sequence of pulses EM (OIS), in this case not associated with the acoustics. The presence of water saturation influences the DIS EM emission.From our experimental observations results that the emission in the ELF and VLF bands is independent from the type of rock, which however condition the deformation history, and form the structural characteristics of the material. In a quarry have observed a similar phenomenon also on large stone masses under strain.These characteristics of the EME may be observed at great distances to monitor the preparation of an Earthquake; in fact radio waves as well as acoustic waves have their maximum propagation at the low frequency band. Wed, 01 Jul 2009 00:00:00 GMT http://hdl.handle.net/2122/5097 Titolo: LARGE SUBSURFACE HOLLOWS REVEALED BY MEANS OF ELECTRICAL RESISTIVITY TOMOGRAPHY : THE CASE OF MT. ARMETTA KARST AREA, ITALY<br/><br/>Autori: Gambetta, M..; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Aicardi, S.; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Armadillo, E.<br/><br/>Abstract: In this work we show the results of a resistivity tomography performedover the shallow part of a large cave system in the Mt.Armetta karst, Pennavaira valley northwestern Italy. The cave has been explored and surveyed by the authors themselves, thus a precise knowledge of size and shape of the subsurface voids is available. The cave, whose shallowest part exhibits narrow passages and large chambers, was developed in the Mesozoic sedimentary cover(Caprauna Armetta tectonic unit), an allochtonous nappe characterized by four deformation phases.The main target of the experiment is a region located at about 30 m below surface precisely spotted by ve 235m long ERT sections.Since cave develops in a windy summit area, the long-term stability of an eolic power plant tower, located over a karst void, is also considered. As a matter of fact, the footings of the eolic towers (approx 100 m high) may interfere with unpredictable shallow hollows, whose presence, in the power plant area, is more than likely. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5021 Titolo: The ‘‘Sirente crater field,’’ Italy, revisited<br/><br/>Autori: Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Ricchetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Etiope, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Rochette, P.; CEREGE, Aix en Provence, France; Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: A scientific debate has developed in the last few years as to whether a 130 m diametersag pond surrounded by a saddle-shaped rim and neighboring smaller sags from theSirente Plain (Abruzzi, Italy) represent the only known Italian meteoritic crater field,a mud volcano, or an anthropogenic feature. To decipher the nature of the Sirentelandforms, we carried out geophysical and geochemical investigations. Geoelectricprofiles document two karstified shelf carbonate ridges lying at 10–40 m depth belowcalcareous lacustrine silts (and deeper more conductive sediments, likely soils/tephra)filling the plain. The smaller sags lie just above the ridges, implying a karstic origin,whereas the main sag (also resting above a carbonate ridge) shows no roots in excess of10–20 m depth, in contrast to the "crater" interpretation. High-resolution magneticsurveys reveal negative/positive anomaly stripes in correspondence with the buried ridges/valleys, respectively. The smaller sags, as well as the main crater are located in the domainof negative residuals. The positive long-wavelength magnetic signature is likely dueto the strongly susceptive soils/tephra filling the buried valleys. Magnetic modeling showsthat the field observed over the crater is incompatible with the field generated by aburied meteorite with realistic characteristics. The smaller sags are characterized bysmall magnetic anomaly couplets, perfectly reproducible considering the susceptibilitycontrast between the fill-in soil and the surrounding silts. Our data show that the Sirentecrater and the minor depressions are simply the results of human activity and karsticprocesses, respectively. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5018 Titolo: Rapid 3-D forward model of potential fields with application to the Palinuro Seamount magnetic anomaly (southern Tyrrhenian Sea, Italy)<br/><br/>Autori: Caratori Tontini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: We show a set of forward model equations in the Fourier domain for calculating the3-D gravity and magnetic anomalies of a given 3-D distribution of density ormagnetization. One property of the potential field equations is that they are given byconvolution products, providing a very simple analytic expression in the Fourier domain.Under this assumption, the domain of the density or magnetization parameters isconnected by a biunivoc relationship with the data space, and potential field anomalies canbe seen as filtered versions of the corresponding density or magnetization distributions.A very fine spatial discretization can be obtained by using a large number of pointswithin a unique 3-D grid, where both the source distributions and field data are defined.The main advantage of this formulation is that it dramatically reduces execution times,providing a very fast forward model tool useful for modeling anomalies at differentaltitudes. We use this method to evaluate an average magnetization of 8 A/m for thePalinuro Seamount in the Tyrrhenian Sea (southern Italy), thus performing a jointinterpretation of morphological and newly acquired magnetic data. Fri, 13 Feb 2009 00:00:00 GMT http://hdl.handle.net/2122/4967 Titolo: Shallow to intermediate resistivity features of the Colfiorito Fault System inferred by DC and MT survey<br/><br/>Autori: Diaferia, I.; Dipartimento di Geologia e di Geofisica, Università degli Studi di Bari, Italy; Loddo, M.; Dipartimento di Geologia e di Geofisica, Università degli Studi di Bari, Italy; Schiavone, D.; Dipartimento di Geologia e di Geofisica, Università degli Studi di Bari, Italy; Siniscalchi, A.; Dipartimento di Geologia e di Geofisica, Università degli Studi di Bari, Italy<br/><br/>Abstract: Over the last decade electromagnetic (EM) measurements have provided new constraints on the upper-crustalstructure of the major fault zones in the world, both when they act as conduit and as a barrier, due to strong sensitivityof resistivity to fluids circulation and mineralization. On the track of a high impact magnetotelluric (MT)study performed across the San Andreas Fault, high resolution EM data were collected in the Colfiorito epicentralarea along profiles crossing some main fault lineaments. Being the study focussed both on shallow that on intermediateresistivity distribution in the brittle upper-crust, a MT profile was integrated by several electrical resistivitytomographies (ERT). The latter were successful in locating faults even where the structures are buried by a widecovering of Quaternary deposits and in the recognition of different electrical signatures of the faults. MT resistivitymodel crossing Mt. Prefoglio normal fault clearly imaged the typical thrust structures of the area and a highconductive zone spatially related to the fault. Seismicity seems to be located outside such conductive area, whosebehaviour suggests a fluidised and altered zone incapable of supporting significant stress internally. Tue, 01 Apr 2008 00:00:00 GMT