http://hdl.handle.net/2122/209 2013-05-23T16:06:39Z http://hdl.handle.net/2122/8034 Title: Birth of an ocean in the Red Sea: Initial pangs Authors: Ligi, M.; CNR-ISMAR Bologna; Bonatti, E.; CNR-ISMAR Bologna; Bortoluzzi, G.; CNR-ISMAR Bologna; Cipriani, A.; CNR-ISMAR Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Science; Carminati, E.; Università di Roma "La Sapienza"; Ottolini, L.; CNR -Pavia; Schettino, A.; Università di Camerino Abstract: We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub- axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly $2.2 and $2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element com- position suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with man- tle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwell- ing form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading. 2012-08-17T22:00:00Z http://hdl.handle.net/2122/8028 Title: Parallel ‘large’ dense matrix problems: application to 3D joint inversion of seismological and gravity data Authors: Tondi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Cavazzoni, C.; CINECA, Interuniversity Computing Centre, Via Magnanelli 6/3, 40033 Casalecchio di Reno (BO), Italy; Danecek, P.; Univ Granada, Inst Andaluz Geofis, E-18071 Granada, Spain; Morelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: To obtain accurate and reliable estimations of the major lithological properties of the rock within a studied volume, geophysics uses the joint information provided by different geophysical datasets (e.g. gravimetric, magnetic, seismic). Representation of the different types of information entering the problem using probability density functions can provide the mathematical framework to formulate their combination. The maximum likelihood estimator of the resulting joint posterior probability density functions leads to the solution of the problem. However, one key problem appears to limit the use of this solver to an extensive range of real applications: information coming from potential fields that implies the presence of dense matrices in the resolving estimator. It is well known that dense matrix systems rapidly challenge both the algorithms and the computing platforms, and are not suited to high-resolution 3D geophysical analysis. In this study, we propose a procedure that allows us to obtain fast and reliable solutions of the joint posterior probability density functions in the presence of large gravity datasets and using sophisticated model parametrization. As it is particularly CPUconsuming, this 3D problem makes use of parallel computing to improve the performance and the accuracy of the simulations. Analysis of the correctness of the results, and the performance on different parallel environments, shows the portability and the efficiency of the code. This code is applied to a real experiment, where we succeed in recovering a 3D shear-wave velocity and density distribution within the upper mantle of the European continent, satisfying both the seismological and gravity data. On a multiprocessor machine, we have been able to handle forward and inverse calculations with a dense matrix of 215.66 Gb in 18 min, 20 s and 20 min, 54 s, respectively. 2012-10-31T23:00:00Z http://hdl.handle.net/2122/7155 Title: Initial burst of oceanic crust accretion in the Red Sea due to edge driven mantle convection Authors: Ligi, M.; Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Bologna; Bonatti, E.; Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Bologna e Lamont Doherty Earth Observatory, Columbia University; Caratori Tontini, F.; GNS Science, Ocean Exploaration Section, New Zealand; Cipriani, A.; Lamont Doherty Earth Observatory, Columbia University; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Schettino, A.; Dipartimento di Scienze della Terra, Università di Camerino; Bortoluzzi, G.; Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Bologna; Ferrante, V.; Istituto di Scienze Marine, Consiglio Nazionale delle Ricerche, Bologna; Khalil, S.; Department of Geological and Biological Sciences, Suez Canal University, Egypt; Mitchell, N.; School of Earth, Atmosphere and Environmental Sciences, University of Manchester; Rasul, N.; Saudi Geological Survey, Saudi Arabia Abstract: The 500 m.y. cycle whereby continents assemble in a single supercontinent and then fragment and disperse again involves the rupturing of a continent and the birth of a new ocean, with the formation of passive plate margins. This process is well displayed today in the Red Sea, where Arabia is separating from Africa. We carried out geophysical surveys and bottom rock sampling in the two Red Sea northernmost axial segments of initial oceanic crust accretion, Thetis and Nereus. Areal variations of crustal thickness, magnetic intensity, and degree of melting of the subaxial upwelling mantle reveal an initial burst of active oceanic crust generation and rapid seafloor spreading below each cell, occurring as soon as the lid of continental lithosphere breaks. This initial pulse may be caused by edge-driven subrift mantle convection, triggered by a strong horizontal thermal gradient between the cold continental lithosphere and the hot ascending asthenosphere. The thermal gradient weakens as the oceanic rift widens; therefore the initial active pulse fades into steady, more passive crustal accretion, with slower spreading and along axis rift propagation. 2011-10-03T22:00:00Z http://hdl.handle.net/2122/7026 Title: Graphical interactive generation of gravity and magnetic fields Authors: Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; von Frese, R.; School ofEarthSciences,TheOhioStateUniversity,Columbus,43210OH,USA Abstract: This paper presents a MATLAB®- based geopotential field generator called GamField that constructs and visualizes subsurface sources in 3-D space and computes their gravity and magnetic effects. GamField also computes anomaly gradients and remanent magnetization effects. The user inputs Cartesian prisms along with their physical properties to fabricate subsurface sources. Examples illustrating the utility of GamField for synthetic anomaly generation of gravity and magnetic fields are shown. ftp://ftp.ingv.it/pub/alessandro.pignatelli/Pignatelli 2011-03-31T22:00:00Z http://hdl.handle.net/2122/7011 Title: Determining geophysical properties of a nearsurface cave through integrated microgravity vertical gradient and electrical resistivity tomography measurements Authors: Gambetta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Armadillo, E.; University of Genova, DIP.TE.RIS, V.le Benedetto XV, Genova —Italy; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stefanelli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Science, 1 Fairway Dr, Avalon, Lower Hutt, New Zealand Abstract: Vertical-gradient microgravity and electrical-resistivity tomography geophysical surveys were performed over a shallow cave in the Italian Armetta Mountain karst area, close to the Liguria-Piedmont watershed. The aim of this study was to test the geophysical response of a known shallow cave. The shallowest portion of the cave exhibits narrow passages and, at about 30 meters below the entrance, a fossil meander linking two large chambers, the target of the geophysical survey. The integrated results of the two surveys show a clear geophysical response to the cave. The surveys exhibited high resistivity values and a negative gravity anomaly over the large cave passages. This work confirms the ability of these geophysical techniques to give the precise location of the voids, even in complex environments. The application of these techniques can be successful for site surveying where the presence of hollows may be expected. 2011-03-31T22:00:00Z http://hdl.handle.net/2122/6689 Title: Graphical interactive generation of gravity and magnetic fields Authors: Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; von Frese, R. Abstract: This paper presents a MATLAB®- based geopotential field generator called GamField that constructs and visualizes subsurface sources in 3-D space and computes their gravity and magnetic effects. GamField also computes anomaly gradients and remanent magnetization effects. The user inputs Cartesian prisms along with their physical properties to fabricate subsurface sources. Examples illustrating the utility of GamField for synthetic anomaly generation of gravity and magnetic fields are shown. ftp://ftp.ingv.it/pub/alessandro.pignatelli/Pignatelli 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6563 Title: Report on the gravimetric, magnetometric, bathymetric activities during Cruise PANSTR10 with R/V Urania: Panarea and Stromboli, Aeolian Islands, 2010-02-05 - 2010-02-15. Authors: Bortoluzzi, G.; CNR-ISMAR Bologna; Del Bianco, F.; CNR-ISMAR Bologna; Maselli, V.; CNR-ISMAR Bologna; Riminucci, F.; CNR-ISMAR Bologna; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muccini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vagni, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cuffaro, M.; Università "La Sapienza", Roma; Palmiotto, C.; Università "La Sapienza", Roma; Rossi, V.; Università "La Sapienza", Roma; Cattafi, I.; Istituto Idrografico della Marina; D'Anna, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Mangano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Rapisarda, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Speciale, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: We present the shipboard activities and preliminary results of Cruise PANSTR10((2010-02-05 2010-02-15)) with R/V Urania. The cruise was scheduled to acquire high resolution magnetometric and gravimetric data on the Panarea and Stromboli volcanic edifices. In addition to this, swath bathymetry and CTD casts were obtained, and five OBS were launched N of Alicudi and on the lineament Stromboli-Marsili, aiming at collecting active and passive seismological data in the Aeolian and Calabrian Arcs. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6562 Title: Determining geophysical properties of a nearsurface cave through integrated microgravity vertical gradient and electrical resistivity tomography measurements Authors: Gambetta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Armadillo, E.; DIP.TE.RIS Università di Genova; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stefanelli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Science, New Zealand Abstract: Vertical-gradient microgravity and electrical-resistivity tomography geophysical surveys were performed over a shallow cave in the Italian Armetta Mountain karst area, close to the Liguria-Piedmont watershed. The aim of this study was to test the geophysical response of a known shallow cave. The shallowest portion of the cave exhibits narrow passages and, at about 30 meters below the entrance, a fossil meander linking two large chambers, the target of the geophysical survey. The integrated results of the two surveys show a clear geophysical response to the cave. The surveys exhibited high resistivity values and a negative gravity anomaly over the large cave passages. This work confirms the ability of these geophysical techniques to give the precise location of the voids, even in complex environments. The application of these techniques can be successful for site surveying where the presence of hollows may be expected. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6306 Title: Multidisciplinary Investigations at Panarea (Aeolian Islands) after the exhalative crisis of 2002-11-02 Authors: Bortoluzzi, G.; CNR-ISMAR Bologna; Aliani, S.; CNR-ISMAR La Spezia; Ligi, M.; CNR-ISMAR Bologna; D'Oriano, F.; CNR-ISMAR Bologna; Riminucci, F.; CNR-ISMAR Bologna; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muccini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Panarea and surrounding Islets form a volcanic edifice, that is part of the Eastern sector of the Aeolian Arc, Southern Tyrrhenian Sea. It is now considered inactive, since last documented activity is 20 Ka old. However, on 2002-11-02, gas started to flow violently from the seafloor in the caldera E of the Island, mainly along NE and NW structural lineaments, and lasting up to 2003-2004 with a consistent flux, orders of magnitude larger that 'steady-state' fumarolic activity documented there in historical times. On the same period a strong effusive activity of Stromboli (10 NM to NNE) was present. Since then, several investigations have been conducted by most important research Institutions at sea and on land, with the aim of focusing the problem, mainly in the light of volcanic surveillance and risk. Among these investigations, some of which have been repeated over years, we present and discuss some data and results from: (a) visual inspection and sampling by divers and ROV, (b) GPS networks and mapping by multibeam and LIDAR, (c) oceanographical measurements by current meters and CTD and water flux and dynamics measurements, (d) magnetic and gravimetric surveys, (e) refraction (OBS and land station networks) and multichannel reflection Seismic, (f) microbiological analysis. Data will be used for compilation of high resolution bathymetric, magnetic and gravimetric maps jointly with data collected by ISMAR since early'90, including the emerged and submerged portions of the edifice. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/5638 Title: Possible causes of arc development in the Apennines, central Italy Authors: Billi, A.; Dipartimento di Scienze Geologiche, Università “Roma Tre,” Largo S.L. Murialdo, 00146 Rome, Italy; Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: In central Italy, the geometry, kinematics, and tectonic evolution of the late Neogene Umbrian Arc, which is one of the main thrusts of the northern Apennines, have long been studied. Documented evidence for orogenic curvature includes vertical axis rotations along both limbs of the arc and a positive orocline test along the entire arc. The cause of the curvature is, however, still unexplained. In this work, we focus our attention on the southern portion of the Umbrian Arc, the so-called Olevano- Antrodoco thrust. We analyze, in particular, gravity and seismic-reflection data and consider available paleomagnetic, stratigraphic, structural, and topographic evidence from the central Apennines to infer spatial extent, attitude, and surface effects of a midcrustal anticlinorium imaged in the CROP-11 deep seismic profile. The anticlinorium has horizontal dimensions of ~50 by 30 km, and it is located right beneath the Olevano- Antrodoco thrust. Stratigraphic, structural, and topographic evidence suggests that the anticlinorium produced a surface uplift during its growth in early Pliocene times. We propose an evolutionary model in which, during late Neogene time, the Olevano- Antrodoco thrust developed in an out-of sequence fashion and underwent ~16° of clockwise rotation when the thrust ran into and was then raised and folded by the growing anticlinorium (late Messinian–early Pliocene time). This new model suggests a causal link between midcrustal folding and surficial orogenic curvature that is consistent with several available data sets from the northern and central Apennines; more evidence is, however, needed to fully test our hypothesis. Additionally, due to the occurrence of midcrustal basement-involved thrusts in other orogens, this model may be a viable mechanism for arc formation elsewhere. 2008-12-31T23:00:00Z