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Romano, Gerardo
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- PublicationOpen AccessUsing the ERT method in tectonically active areas: hints from Southern Apennine (Italy)(2008-11)
; ; ; ; ; ; ; ; ; ; ;Giocoli, A.; Istituto di Metodologie per l’Analisi Ambientale – CNR – Tito (PZ), Italy ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Galli, P.; Dipartimento della Protezione Civile, Rome, Italy ;Lapenna, V.; Istituto di Metodologie per l’Analisi Ambientale – CNR – Tito (PZ), Italy ;Piscitelli, S.; Istituto di Metodologie per l’Analisi Ambientale – CNR – Tito (PZ), Italy ;Rizzo, E.; Istituto di Metodologie per l’Analisi Ambientale – CNR – Tito (PZ), Italy ;Romano, G.; Istituto di Metodologie per l’Analisi Ambientale – CNR – Tito (PZ), Italy ;Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Universit`a di Bari, Bari, Italy ;Magrì, C.; Dipartimento di Geologia e Geofisica, Universit`a di Bari, Bari, Italy ;Vannoli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ; ; Electrical Resistivity Tomography (ERT) method has been used to study two tectonically active areas of southern Apennine (Caggiano Faults and Ufita Basin). The main aim of this job was to study the structural setting of the investigated areas, i.e. the geometry of the basins at depth, the location of active faults at surface, and their geometrical characterization. The comparison between ERT and trench/drilling data allowed us to evaluate the efficacy of the ERT method in studying active faults and the structural setting of seismogenic areas. In the Timpa del Vento intermontane basin, high resolution ERT across the Caggiano Fault scarps, with different arrays, electrode spacing (from 1 to 10 m) and penetration depth (from about 5 to 40 m) was carried out. The obtained resistivity models allowed us to locate the fault planes along the hillslope and to gather information at depth, as later con-firmed by paleoseismological trenches excavated across the fault trace. In the Ufita River Valley a 3560-m-long ERT was carried out across the basin, joining 11 roll-along multi-channel acquisition system with an electrode spacing of 20mand reaching an investigation depth of about 170 m. The ERT allowed us to reconstruct the geometry and thickness of the Quaternary deposits filling the Ufita Valley. Our reconstruction of the depositional setting is in agreement with an interpretative geological section based on borehole data.323 273 - PublicationOpen AccessMobility of pyroclastic flows(2011-04-08)
; ; ;Cagnoli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Romano, G. P.; Engineering Department, La Sapienza University, Rome; see uploaded document124 119 - PublicationOpen AccessGeophysical multidisciplinary investigation of the structure of an unstable flank: the NE sector of Mt. Etna.(2014-09-09)
; ; ; ; ; ; ; ; ;Bonforte, Alessandro; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Cocina, Ornella; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Siniscalchi, Agata; Università degli Studi di Bari ;Barberi, Graziella; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Guglielmino, Francesco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Romano, Gerardo; Università degli Studi di Bari ;Sicali, Simona; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Tripaldi, Simona; Università degli Studi di Bari; ; ; ; ; ; ; Mount Etna is characterized by a complex regional tectonics with a N-S compression related to the Africa – Europe convergence that interacts with a WNW-ESE extension associated to the Malta Escarpment. A general eastward motion is present in the eastern flank. Although the existence of these phenomena is overt, the geometry of the sliding sector is still debated. The non-uniqueness of the geophysical inverse models and the different limitations in resolution and sensitivity of each technique spurred us to undertake, in the frame of the MEDiterranean Supersites Volcanoes (MED-SUV) project, a joint interpretation of independent data in order to better constrain the results. Seismic data come from the network run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) – Osservatorio Etneo, Sezione di Catania. The relocated seismicity defines two main seismogenic volumes in the NE sector of the volcano: the first cluster is related to the known Pernicana Fault system, while the second one is located southwards, beneath the northern wall of the Valle del Bove. The resistivity models come from a MT survey carried out on the eastern flank of the volcano and consisting of thirty broad-band soundings along N-S and NW-SE oriented profiles. The resistivity modeling of MT profiles reveal three major layers in a resistive-conductive-resistive sequence. A low resistivity volume is clearly identified on the NE flank of the volcano, between The Pernicana fault and the northern wall of the Valle del Bove. Ground deformation studies (GPS and InSAR) revealed the segmentation of the unstable flank and define the NE sector as the most mobile one; this sector is perfectly bounded by the two seismic clusters and corresponds to the low resistivity volume. The sliding surface modeled by ground deformation data inversions well matches in depth with a resistivity transition and with two seismogenic layers.252 84 - PublicationOpen AccessMobility of Pyroclastic Flows and Rock Avalanches(2010-05-31)
; ; ;Cagnoli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Romano, G.; Università La Sapienza; Rapid mass movements of rock fragments are among the most hazardous natural phenomena. The ability to foresee their mobility is important when assessing natural hazards in volcanic regions. The dynamics of granular flows is however a challenging multivariate problem. Among the variables that affect their mobility we can include grain size and flow volume. Unfortunately, there are no generally accepted scaling laws describing these phenomena with the certainty to have taken into consideration all important aspects of nature. There are also different ways to assess mobility. Some authors, for example, adopt the distance travelled by the flow front or other arbitrary distances which are inappropriate for energy budget considerations because these flows deform during motion and deposition. Because of the difficulties inherent in direct field observations of these catastrophic events, we resort to laboratory experiments where granular material is released down a chute whose shape is similar to the profile of Mayon Volcano in the Philippines. Our experiments show that in flows of angular rock fragments, the smaller the grain size (all the other things equal), the larger is mobility. Importantly, this mobility is assessed measuring the distance travelled by centres of mass. Particle image velocimetry analysis of high speed video camera images shows also that the smaller the grain size, the smaller is the agitation of the fragments. This can explain the increase of runout distance as grain size decreases because fragments that are less agitated dissipate less energy. This should also explain why larger flow volumes are known to be more mobile. The larger the volume, the relatively smaller is the mass of a fragment with respect to the total mass of the flow so that fragments of larger flows are less agitated and for this reason dissipate less energy.160 68 - PublicationOpen AccessStudio dell'anisotropia elettrica nella zona della sorgente sismogenetica del terremoto dell’Irpinia del 1930(2007-11)
; ; ; ; ; ; ; ; ; ; ;Balasco, M.; Istituto per le Metodologie Applicate all’Ambiente - CNR, Marsico Nuovo (PZ), Italia ;Diaferia, I.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia ;Di Bucci, D.; Dipartimento della Protezione Civile, Roma, Italia ;Fracassi, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Loddo, M.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia ;Magrì, C.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia ;Romano, G.; Istituto per le Metodologie Applicate all’Ambiente - CNR, Marsico Nuovo (PZ), Italia ;Schiavone, D.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia ;Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia ;Tripaldi, S.; Dipartimento di Geologia e Geofisica, Università di Bari, Bari, Italia; ; ; ; ; ; ; ; ; L’area del terremoto dell’Irpinia del 1930 corrisponde in profondità all'avampaese Apulo, inflesso al di sotto delle unità alloctone accavallate nella porzione frontale del cuneo orogenico, ma non coinvolto nelle strutture dei cosiddetti duplex dell'Apula sensu Patacca and Scandone (2004). In particolare, le profondità ipocentrali del terremoto del 1930 corrispondono al basamento sottostante la successione della Piattaforma Carbonatica Apula. Il campo macrosismico e i dati strumentali disponibili (si veda la sorgente in DISS, 2007, con relativa bibliografia, e Pino et al., sottomesso) suggeriscono una sorgente sismogenetica con un’orientazione e una cinematica che rappresentano una sorta di transizione tra la direzione W-E a cinematica trascorrente destra, che caratterizza la sismicità propria delle aree di avampaese sia affiorante che sepolto, e la direzione NW-SE a cinematica normale, che caratterizza la sismicità connessa all'estensione lungo l'asse della catena Appenninica (si veda il terremoto del 1980). In questo quadro, l’obiettivo dello studio magnetotellurico è stato quello di investigare i volumi di crosta al di sotto della successione Apula per valutare l'eventuale presenza di direzioni preferenziali dell'anisotropia di resistività che fossero confrontabili con la direzione della sorgente del terremoto del 1930. Il verificarsi di tale evenienza avrebbe potuto essere infatti interpretato come indizio di una zona di debolezza regionale, che avrebbe condizionato le caratteristiche geometriche e cinematiche della sorgente del terremoto stesso. Partendo dall’area sismogenetica segnalata nel DISS per questo terremoto, sono stati effettuati in un’area di circa 1000 km2 sondaggi magnetotellurici in 15 siti, nell’intervallo di 0.009- 4000 s. Per ciascun sito si è proceduto alla misura delle tre componenti ortogonali del campo magnetico e di tre componenti del campo elettrico, di cui due lungo la stessa linea e ortogonali alla terza. Ciò ha consentito la stima dei parametri magnetotellurici per due sondaggi adiacenti, al fine di meglio controllare possibili problemi di rumore antropico o strumentale. Le stazioni, fino ad un massimo di tre, hanno operato in contemporanea fungendo l’una per l’altra da remote reference (Gamble et al., 1979). Va sottolineata la buona qualità dei dati acquisiti sia in termini di stime stabili con diverse tecniche di analisi, che per basso scattering delle curve di resistività apparente e fase. Le risposte sperimentali sono state poi comparate con i dati di pozzo disponibili, verificando un ottimo accordo. È stata inoltre eseguita un’analisi sulle proprietà fisiche e geometriche del tensore impedenza, adottando lo schema di decomposizione di Weaver et al. (2000) dal quale è derivato poi lo studio degli invarianti magnetotellurici per la definizione della dimensionalità delle strutture elettriche investigate ai vari periodi (ovvero alle varie profondità). Circa il 75% dei dati analizzati implica strutture assimilabili necessariamente a modelli tridimensionali e le quattro componenti del tensore impedenza sono significativamente diverse da zero. Per questo tipo di strutture, seguendo Weaver et al. (2000), è comunque possibile definire una direzione di eterogeneità elettrica. Ciò è stato fatto per ciascun sondaggio e per ciascun periodo di stima. Mediante la trasformazione di Niblett–Bostick è stato poi ottenuto lo strike elettrico in funzione della profondità stimata. Viene riportata la direzione di strike per i vari sondaggi alla profondità stimata nell’intervallo 8 - 16 km, riferibile quindi a una porzione di crosta al di sotto del resistivo che identifica le successioni della Piattaforma Apula.276 83 - PublicationOpen AccessGeological and geo-structural characterization of the Montemurro area (Southern Italy) inferred from audiomagnetotelluric surveyThis paper presents the results obtained by an audio-magnetotelluric (AMT) survey carried out crossing the western sector of Montemurro village (Southern Italy) affected by an intense hydrogeological instability. The AMT investigation was aimed to settle the question concerning the possible prosecution toward SE of the Eastern Agri Fault System whose surficial evidences could be blinded by extensive landslides phenomena and by anthropization of the territory. The AMT profile was oriented in NE-SW direction, orthogonal to the main geological structures of the investigated area. It crossed longitudinally the area affected by instability. The AMT model provides new insights on already known faults (i.e. Montemurro Faults) and imaged their in-depth immersion thus answering to still open geological question in the investigated areas. Furthermore, the high resolution of the model allowed the imaging of the boundaries, in terms of resistivity contrast, between material affected/unaffected by the sliding dynamics or characterized by an higher water content. The results provide new knowledge about the geological and geoelectrical structures in the area. They will be fully integrated with the results of the on-going research activities in the area and will represent an additional step for the multiscale and multiparametrical characterization of the Agri Valley geological setting.
103 62 - PublicationRestrictedVertical segregations in flows of angular rock fragments: Experimental simulations of the agitation gradient within dense geophysical flows(2013)
; ; ;Cagnoli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Romano, G. P.; Ingegneria, La Sapienza; In this paper, we illustrate laboratory experiments whose purpose is to study the vertical segregations that are commonly observed in deposits of dense geophysical flows (such as pyroclastic flows and rock avalanches). In these experiments, we use rock cuboids with 5 mm long edges as matrix and rock cuboids with 2 cm long edges as segregating clasts. A rotating disk is used to apply frictional stresses at the base of the granular masses. In our experiments, segregating cuboids with density smaller than or equal to that of the matrix particles rise whereas segregating cuboidswith density larger than that of the matrix particles sink. The granular flows are imaged through the glass container of the experimental apparatus by a high-speed video camera at 2000 fps. By means of particle image velocimetry analysis of the movies, we study the vertical gradient of particle agitation that exists within the granular flows where agitation increases downward because of the interaction with the subsurface asperities. The high-speed movies show that it is the particle agitation within the flows that exerts an upward force and that, when this force is larger than theweight of the segregating clast, the clast riseswhereas, when it is smaller, the clast sinks. The most important result in our set of experiments is that the threshold which separates the values of density of the segregating clasts that segregate upward and the values of density of the segregating clasts that segregate downward is larger than the density of the matrix particles. This explains the upward segregation of dense lithics that is frequently observed in deposits of geophysical flows. This upward segregation is due to the fact that the resultant of the collisions exerted by the matrix particles is a force strong enough to push upward also dense and heavy fragments.230 47 - PublicationOpen AccessA new magnetotelluric monitoring network operating in Agri Valley (Southern Italy): study of stability of apparent resistivity estimates(2008-02)
; ; ; ; ; ;Balasco, M.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy, ;Lapenna, V.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy, ;Romano, G.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy, ;Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, Italy ;Telesca, L.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy,; ; ; ; Variations detected in geophysical, especially electromagnetic, parameters in seismic active areas have been sometimes attributed to modifications of the stress field. Among the different geophysical methods, magnetotellurics (MT) could be one of the most effective because it allows us to explore down to seismogenic depths. Continuous MT recording could allow us to evaluate whether possible variations are significantly correlated with the seismic activity of investigated area. To assess the significance of such observations we must be able to say how well an apparent resistivity curve should be reproduced when measurements are repeated at a later time. To do this properly it is essential to know that the estimated error bars accurately represent the true uncertainties in comparing the transfer functions. In this work we will show the preliminary results obtained from the analysis of the data coming from the new MT monitoring network installed in Agri Valley. This analysis gives us the possibility: i) to better study the temporal stability of the signals, ii) to better discriminate the noise affecting the measures by remote reference estimation. The performed analysis disclosed a relatively low degree of noise in the investigated area, which is a promising condition for monitoring.255 229 - PublicationRestrictedEffect of grain size on mobility of dry granular flows of angular rock fragments: An experimental determination(2010-03-25)
; ; ;Cagnoli, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Romano, G.; Università La Sapienza; Rapid mass movement of rock fragments are among the most hazardous natural phenomena. They are too dangerous to be approached and studied directly and, for this reason, experiments are necessary to understand their flow mechanisms. Here, we present the results of experiments on granular flow mobility obtained releasing batches of angular rock fragments down a curved chute. Our experiments demonstrate that the finer the grain size of the flow, the larger its mobility. This is accompanied by a decrease of fragments agitation when grain size decreases as shown by particle image velocimetry measurements of high-speed video camera images. The smaller the agitation, the smaller is also the energy dissipated by flows per unit of travel distance. This explains the effect of finer grain size on flow mobility. These results are an important step towards the prediction of runout distances as a function of the features that characterize the different geophysical flows.157 19 - PublicationOpen AccessA new magnetotelluric monitoring network operating in Agri Valley (Southern Italy): study of stability of apparent resistivity estimates(2008-02)
; ; ; ; ; ;Balasco, M.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy ;Lapenna, V.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy ;Romano, G.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy ;Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, Italy ;Telesca, L.; Istituto di Metodologie per l’Analisi Ambientale, CNR, Tito Scalo (PZ), Italy; ; ; ; Variations detected in geophysical, especially electromagnetic, parameters in seismic active areas have been sometimes attributed to modifications of the stress field. Among the different geophysical methods, magnetotellurics (MT) could be one of the most effective because it allows us to explore down to seismogenic depths. Continuous MT recording could allow us to evaluate whether possible variations are significantly correlated with the seismic activity of investigated area. To assess the significance of such observations we must be able to say how well an apparent resistivity curve should be reproduced when measurements are repeated at a later time. To do this properly it is essential to know that the estimated error bars accurately represent the true uncertainties in comparing the transfer functions. In this work we will show the preliminary results obtained from the analysis of the data coming from the new MT monitoring network installed in Agri Valley. This analysis gives us the possibility: i) to better study the temporal stability of the signals, ii) to better discriminate the noise affecting the measures by remote reference estimation. The performed analysis disclosed a relatively low degree of noise in the investigated area, which is a promising condition for monitoring.236 115