http://hdl.handle.net/2122/390 2013-05-22T11:44:30Z http://hdl.handle.net/2122/8475 Title: Very detailed seismic pattern and migration inferred from the April 2010 Pietralunga (northern Italian Apennines) micro-earthquake sequence Authors: Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Cattaneo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Monachesi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Frapiccini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: We propose a very detailed picture of the seismicity occurring in the proximity of the Alto Tiberina Low Angle Normal Fault (ATF, Northern Italian Apennines) by presenting the pattern and evolution of a seismic sequence that occurred on the hanging wall of the ATF in the first months of 2010 and that was characterized by about 1000 events with ML ranging from -0.7 to 3.8. In order to capture the rupture kinematics of the investigated area, a cross-correlation technique was at first applied to calculate very accurate time shifts among the events of the sequence and then to relocate them. Considering the many factors that can affect the accuracy of a routine event location, the whole sequence was relocated with the double-difference method, including both absolute travel-time measurements and cross-correlation differential travel-times. The new locations confirm that seismic activity is mainly arranged along a NW-SE oriented structure, ranging in depth from 4 to 6 km and dipping towards North East with an angle of about 65°. A further analysis of waveforms similarity was performed at a reference station by merging the capability of the cross-correlation technique and the bridging algorithm. The analysis allows us to group events into several earthquake families (from now on multiplets), 11 of which include at least 10 events with a cross-correlation value higher than 0.9. The detected mutiplets allow us to emphasize the spatial and temporal migration of the sequence occurred along a 307°N strike direction with an averaged propagation velocity of about 0.4 km/day. The normal focal mechanisms obtained from the events with ML≥2 validate the supposed extensional tectonic regime of the investigated area. The main nodal planes, characterized by strikes ranging in 312°±12 and dips about -90°, are consistent with the spatial evolution of the aftershocks. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8437 Title: Combining model and geostationary satellite data to reconstruct the hourly SST field over the Mediterranean Sea Authors: Marullo, S.; Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, ENEA; Santoleri, R.; CNR Istituto di Scienze dell'Atmosfera e del Clima; Ciani, D.; CNR Istituto di Scienze dell'Atmosfera e del Clima; Le Borgne, P.; Meteo-France/DP/CMS; Pere, S.; Meteo-France/DP/CMS; Pinardi, N.; Dipartimento di Scienze Ambientali, Universita' di Bologna; Tonani, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Nardone, G.; Istituto Superiore per la Protezione e la Ricerca Ambientale Abstract: This work focuses on the Sea Surface Temperature diurnal cycle reconstruction over the Mediterranean Sea by combining numerical model analyses and geostationary satellite measurements. Our approach is to take advantage of geostationary satellite observations as the diurnal signal source to produce gap‐free optimally interpolated (OI) hourly SST fields using model analyses as first guess. The work is focused on summer 2011 including all the data and model output from June 1st to August 31st 2011. The OI interpolation estimate, the model first guess (provided by an operational forecasting model) and the SEVIRI data (provided by O&SI SAF) were evaluated using drifter and mooring data as a references. Special attention was devoted to the analysis of Diurnal Warming (DW) events that were particularly frequent during this period. Results suggest the following: 1) the model reproduces quite well the Mediterranean SST diurnal cycle with the exclusion of intense DW events but the amplitude of the model cycle is often less intense than the corresponding SEVIRI and drifter observations, due to the different thickness of the surface ocean layer they represent. Time shifts between model and data warming/cooling phases of the day are also discussed. 2) The Diurnal OI SST field (DOISST), resulting from the blending of model and SEVIRI data via optimal interpolation, well reproduces the diurnal cycle (including DW events) leaving substantially unchanged the statistics of the difference between SEVIRI and drifter measurements also in data void positions where the interpolation operates. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8358 Title: Monitoraggio della microsismicità naturale e/o indotta nel periodo maggio 2011 – aprile 2012, Sito di Cortemaggiore. Rendiconto Maggio 2012 Authors: Augliera, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Franceschina, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Lovati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: unavailable 2012-04-30T22:00:00Z http://hdl.handle.net/2122/8204 Title: Statistical investigation of site effects using earthquake and ambient noise recordings (part 2): reconstruction of earthquake spectral ratio from noise Authors: De Rubeis, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cadet, H.; A.D.R.G.T. (SAGE), Association for the Development of Research in Land Slides, Gières, France; Bard, P.-Y.; ISTerre, CNRS, IFSTTAR, Université de Grenoble, Grenoble, France; Theodoulidis, N.; ITSAK-EPPO, Institute of Engineering Seismology and Earthquake Engineering, Thessaloniki Geece Abstract: Standard spectral ratio from earthquake recordings (SSR) is considered the reference empirical method for assessing site effects as a function of frequency. However, other estimates can be easily obtained from noise measurements (i.e., Horizontal-to-Vertical Spectral Ratio, HVN), even though their reliability in terms of amplitude is controversial. In the framework of the ToK ITSAK-GR (2006-2010) and NERA (2007-2013) EC projects. Recordings from 64 sites from very different geographical areas where analyzed in the companion paper Cultrera et al. (2012); The authors evidenced statistically significant correlations between SSR and HVN through an appropriate linear combination of spectral ratio amplitudes using the canonical correlation technique. In the present paper we go one step further and show how to estimate the SSR spectral ratio of specific sites when only single station noise measurements are available, using the results of the canonical correlation analysis between SSR and HVN recorded at several sites and pertaining to the same area. A sistematic SSR evaluation has been conducted and tested by a cross validation procedure: the expected SSR at each validation site are in turn estimated by a weighted average of the SSR values measured at the other sites; the weights are properly set to account more for the sites with similar behavior in terms of the canonical correlation results between HVN and SSR. To evaluate the goodness of the estimation, we compared all the inferred and the original SSR, and we performed a critical analysis on the spectral characteristics of earthquake site response as recovered from noise measurements. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8203 Title: Statistical investigation of site effects using earthquake and ambient noise recordings (part 1): correlations between different estimates. Authors: Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; De Rubeis, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Theodoulidis, N.; Institute of Engineering Seismology and Earthquake Engineering (EPPO-ITSAK), Thessaloniki, Greece; Bard, P.-Y.; Institut des Sciences de la Terre (ISTerre), Risques, Grenoble, France Abstract: The Horizontal-to-Vertical Spectral Ratio from earthquake recordings (HVSR) and from ambient noise recordings (HVN) realistically indicate fundamental frequency but, for the majority of the worldwide examined sites, they do not provide reliable amplification curves as predicted by the earthquake Spectral Ratio to a reference site (SSR). Given the fact that HVSR and especially HVN can be easily obtained, it is challenging to search for a meaningful correlation with SSR amplification functions in the whole frequency band. To this aim we used recordings from 75 sites worldwide and we applied a multivariate statistical approach (the canonical correlation analysis) to investigate and quantify any correlation among spectral ratios and, from a subset of sites in sedimentary basins, with geometrical and geophysical parameters (S-wave velocity and the 2D geometry of the valley). Results show a correlation between SSR and HVN or HVSR that can be statistically quantified, and it is modulated in specific frequency range. Moreover, the larger are the Vs30, the bedrock depth and the valley’s shape ratio, the higher is the low-frequency amplitude in HVSR and HVN, and the lower is the high-frequency value. Despite the limitation of the database, the correlation results can be used to estimate the excepted SSR spectral ratio of specific sites in the investigated areas when only noise measurements are available(see the companion paper De Rubeis et al., 2012). 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8163 Title: Accounting for source effects in the ShakeMap procedure: the 2000 Tottori and the 2008 Miyagi earthquakes Authors: Spagnuolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Faenza, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Herrero, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Michelini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: Recently, there have been great improvements in real-time seismology. At present, source parameters are available within a few tens of minutes after the earthquake occurrence and there is an evidence that this time will be further reduced, in terms of efficiency of real time transmission and increasing data coverage. In this context, together with the development of new ground motion predictive equations (GMPEs) able to account for source complexity, the generation of maps of strong ground motion shaking in quasi real-time has become ever more feasible after the occurrence of a damaging earthquake. However, GMPEs may not reproduce faithfully the ground motion in the near source region if the finiteness of the causative fault is not taken into account. In this work, we test the effectiveness of refined GMPEs to improve the accuracy of the ShakeMap software package in the generation of the shakemaps. The test is conducted controlling the performance of ShakeMap as we decrease the amount of the available data. We then update ShakeMap with the equations derived within the NGA project (Power et al. 2008) in order to better constrain source effects that are likely to influence strongly the level of ground shaking. In order to conduct the test properly, we select an area as dense as needed to ensure an objective appraisal of the results. We investigate two well-recorded events from Japan: the 2008 Iwate-Miyagi (Mw7) and the 2000 Tottori (Mw6.6) events. The results outline that these equations can capture some aspects of the ground shaking, in particular the effects that depend the most on the earthquake source. Nevertheless, the huge scatter of real data respect to the distance from the source is not fully embedded inside the predictive equations, and the strong variability maybe attributable to other multidimensional effects, like propagation effects and local site amplification. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7738 Title: Le fasi di colluviamento tardoantiche nel Piano della Civita e la fine della frequentazione dell'abitato di Alba Fucens. Atti del Convegno in memoria di Joseph Mertens. Authors: Galadini, Fabrizio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ceccaroni, Emanuela; Soprintendenza dei Beni Archeologici dell'Abruzzo; Falcucci, Emanuela; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Gori, Stefano; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: L’evidenza di abbandono di un abitato antico successivamente ad un forte terremoto porta logicamente ad ipotizzare una relazione diretta tra i due eventi. Ciò vale tanto più in riferimento all’età tarda, considerando che la catastrofe naturale potrebbe inserirsi in un quadro di decadenza preesistente dell’insediamento. Un’ipotesi come questa potrebbe toccare Alba Fucens, ove sono chiare e numerose le evidenze del terremoto tardoantico e ancora più chiaro è il fatto che l’insediamento, a un certo punto della sua storia e successivamente al terremoto, fu abbandonato. Tuttavia, su un piano generale, è opportuno sottolineare che la tesi secondo cui l’abbandono di un abitato antico sia da riferirsi esclusivamente a un forte terremoto deve essere sottoposta ad analisi di più ampia prospettiva. Queste devono coinvolgere aspetti difficilmente quantificabili, come gli effetti sulla popolazione del venir meno del tessuto urbanistico ed edilizio o – in senso ancora più ampio – la risposta delle società antiche alle ovvie ricadute economiche a scala locale o al cambiamento del tessuto relazionale con il territorio pure sinistrato. Le informazioni archeologiche relative ad Alba Fucens sembrano alimentare l’ipotesi della continuità abitativa su un ampio arco cronologico plurisecolare che include il momento dell’evento sismico, secondo il modello generale dello sviluppo “verticale”, in situ, degli abitati antichi periodicamente afflitti dalle conseguenze dei terremoti distruttivi, suggerito – a esempio – nel lavoro di Ambraseys (2005). In effetti, già Mertens (1991) citò le evidenze stratigrafiche di una continuità della vita nell’abitato di Alba colpito dal terremoto1, seppure con modalità precarie. Tali evidenze possono essere affiancate i) alle tracce di continuità abitativa tra Tarda Antichità e Alto Medioevo discusse nei più recenti lavori di Redi (2001) e Tulipani (2006) e ii) al ritrovamento di resti di strutture abitative tarde o altomedievali nel piazzale antistante il santuario di Ercole nelle ultime campagne di scavo (2008-2009). Sono altresì compatibili con la fonte che cita l’accampamento di militari bizantini durante la guerra gotica (Procopio, Bell. Goth., II, 7). Tutte 1 - Tale evento sismico è attributo da Mertens (1991) al IV secolo d.C.; in precedenza, l’autore (Mertens, 1981) aveva riferito di “catastrofi che si abbatterono sulla città alla fine del IV e nel corso del V secolo”. Il terremoto è invece attribuito al V-VI secolo da Galadini (2006) e Galadini et al. (2010). 2 evidenze e vicende apparentemente successive al terremoto distruttivo. Sembra pertanto chiaro che le ragioni dell’abbandono definitivo e completo dell’abitato storico non siano da riferirsi soltanto agli effetti – diretti e forse nemmeno indotti e di lungo periodo – dell’evento sismico tardoantico. In questo articolo, dopo una breve sintesi sullo stato delle conoscenze relative al terremoto che nella Tarda Antichità colpì Alba Fucens, si fornirà un’interpretazione sull’origine dei sedimenti che ricoprivano i resti archeologici prima delle attività di scavo. Tali successioni, risultanti dai processi sedimentari naturali e culturali che hanno interessato l’area dell’abitato antico, saranno descritte in dettaglio nell’Appendice 1. Nella prospettiva di questa analisi, sembra utile segnalare che, dal punto di vista geomorfologico, il Piano della Civita – area che ospita i resti attualmente visibili della città – si deve considerare come una sorta di piccolo bacino, cioè come un’entità fisiografica naturalmente predisposta alla sedimentazione, in funzione delle condizioni al contorno, rappresentate sostanzialmente dalla stabilità dei versanti adiacenti. L’interpretazione in termini di modalità deposizionale delle varie unità stratigrafiche che riempivano il Piano della Civita e la definizione dell’età della sedimentazione forniranno spunti per meglio definire la storia ambientale del sito e i suoi effetti sull’insediamento di Alba Fucens. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7348 Title: Determining the origin of carbon dioxide and methane in the gaseous emissions of the San Vittorino plain (central Italy) Authors: Giustini, F.; CNR; Blessing, M.; BRGM; Brilli, M.; CNR; Lombardi, S.; University La Sapienza; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We are presenting here both chemistry and isotope ratios of helium (He), carbon (13C) and hydrogen (D) of free gases collected in the San Vittorino plain, an intramontane depression of tectonic origin, in order to provide new constraints to better understand mantle degassing in central Italy. Carbon isotopic composition of the carbon dioxide (δ13C-CO2 -2.0‰ to -3.8‰) and He isotope ratios (R/RA 0.12 to 0.27) are used to calculate the fraction of CO2 originating from mantle degassing versus sedimentary sources. Results show that CO2 predominantly (average of 80%) derives from thermo-metamorphic reaction of limestone. The remaining 20% are attributed to a mantle source. The presence of tectonic dislocations allows upward gas migration from a deep source to the Earth’s surface, not only in the peri-Tyrrhenian sector, but also in the more eastern part of central Italy. Isotope ratios of methane (13C-CH4 -6.1‰ to -22.7‰; D-CH4 -9‰ to -129‰) shows that the gas vent releases gas of thermogenic origin, involving CO2 and/or organic matter. Methane seems not to be related to mantle or magma degassing, but seems to be affected by microbial oxidation process. 2010-12-31T23:00:00Z http://hdl.handle.net/2122/7331 Title: Soil gas geochemistry for the study of far- and near-field gas migration mechanisms. Authors: Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Beaubien, S. L.; Universy La Sapienza; Lombardi, S.; Univeristy La Sapienza Abstract: Detailed soil-gas surveys have been conducted at two mine districts to better comprehend gas migration mechanisms from deposits buried at different depths. The Tolfa (Lazio, Central Italy) and Neves-Corvo (Baixo Alentejo, Portugal) mine districts have different characteristics: the former is superficial (30-100 m) while the latter is located at a depth of 400-500 m and covered by low-permeability metamorphic rocks. The soil-gas results from these two different investigated areas provide interesting results related to the study of far- and near-field gas migration mechanisms. In particular, the anomalous concentrations of sulphur compounds (COS, CS2 e SO2), CO2, and Rn confirmed the presence of the two ore deposits. Furthermore, radon was found to be sensitive to soil permeability variations and to be associated with migration pathways (faults and/or fractures). Overall the results indicate the potential for using the studied gas species as indicators of deep seated ore deposits (i.e. in the Neves-Corvo mine district), even at locations where there is thick overburden and no surface evidence. 2010-12-31T23:00:00Z http://hdl.handle.net/2122/6928 Title: On deformation sources in volcanic areas: modeling the Campi Flegrei (Italy) 1982-84 unrest Authors: Trasatti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Bonafede, M.; Università di Bologna; Ferrari, C.; Università di Bologna; Giunchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Berrino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: Deformation sources in volcanic areas are generally modeled in terms of pressurized tri-axial ellipsoids or other cavities with simple geometrical shapes embedded in homogeneous half-spaces. However, the assumption of a particular source mechanism and the neglect of medium heterogeneities bias significantly the estimate of source parameters. Leveling and EDM data, collected during the 1982-84 unrest episode at Campi Flegrei (Italy), are employed to retrieve source parameters according to a Bayesian inversion procedure, considering the heterogeneous elastic structure of the volcanic area. We describe a general deformation source in terms of a suitable moment tensor, through 3D finite element computations. Best fitting moment tensors are found to be incompatible with any pressurized ellipsoid. Taking into account the deflation of a deeper magma reservoir, which accompanies the inflation of the shallower moment source, data fit improves considerably but the retrieved moment tensor of the shallow source is found to be incompatible with pressurized ellipsoids, still. Looking for alternative physical models of the deformation source, we find that the best fit moment tensor can be best interpreted in terms of a mixed-mode (shear and tensile) dislocation at 5.5 km depth, striking EW and dipping by 30 to the North. Gravity changes are found to be compatible with the intrusion of 60·106 m3 of volatile rich magma with density 2000 kg/m3. 2009-12-31T23:00:00Z