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Scaltrito, Antonio
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Scaltrito, Antonio
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antonio.scaltrito@ingv.it
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- PublicationOpen AccessSeismological and structural constraints on the 2011–2013, Mmax 4.6 seismic sequence at the south-eastern edge of the Calabrian arc (North-eastern Sicily, Italy)(2018)
; ; ; ; ; ; ; ; ; ;; ; ; ;; Between June 2011 and September 2013, the Nebrodi Mountains region was affected by a seismic swarm consisting of > 2700 events with local magnitude 1.3 ≤ ML ≤ 4.6 and located in the 5–9 km depth interval. The seismic swarm defines a seismogenetic volume elongated along the E-W direction and encompasses the NW-SE-oriented tectonic boundary between the Calabrian arc (north-eastward) and the Sicilide units (south-westward). By exploring the recent tectonic deformation and the seismic behavior of the region, this study aims at providing additional constraints on the seismogenetic faults at the southern termination of the Calabrian arc. Waveform similarities analysis allowed observing that ~ 45% of the whole dataset can be grouped into six different families of seismic events. Earthquake multiplet families are mainly located in the eastern part of the seismogenetic volume. We suggest that such a feature is responsive to the lateral lithological variations as highlighted by geology (at the surface) and P-wave seismic tomography (at depth of 10 km). Stress tensor inversions performed on FPSs indicate that the investigated region is currently subject to a nearly biaxial stress state in an extensional regime, such that crustal stretching occurs along both NW-SE and NE-SW directions. Accordingly, mesoscale fault geometries and kinematics analyses evidence that a younger normal faulting stress regime led to a tectonic negative inversion by replacing the pre-existing strike-slip one. Based on our results and findings reported in recent literature, we refer such a crustal stretching to mantle upwelling process (as evidenced by diffuse mantle-derived gas emissions) coupled with a tectonic uplift involving north-eastern Sicily since Middle Pleistocene. Moreover, seismic swarms striking the region would be related to the migration of mantle and sub-crustal fluids toward the surface along the complex network of tectonic structures cutting the crust and acting as pathways.280 30 - PublicationRestrictedCrustal seismic velocity in the Marche region (Central Italy): computation of a minimum 1-D model with seismic station corrections.(2009)
; ; ; ; ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Imposa, S.; Dipartimento di Scienze Geologiche, Università di Catania ;Raffaele, R.; Dipartimento di Scienze Geologiche, Università di Catania ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; A 1-D velocity model for the Marche region (central Italy) was computed by inverting P- and S-wave arrival times of local earthquakes. A total of 160 seismic events with a minimum of ten observations, a travel time residual ≤ 0.8 s and an azimuthal gap lower than 180° have been selected. This “minimum 1-D velocity model” is complemented by station corrections, which can be used to take into account possible near-surface velocity heterogeneities beneath each station. Using this new P-wave velocity model and the program HYPOELLIPSE (Lahr, 1999), the selected local events were relocated. Earthquake locations in this study are of higher quality with respect to the original ones. The obtained minimum 1-D velocity model can be used to improve the routine earthquakes locations and represents a further step towards more detailed seismotectonic studies of the area.255 31 - PublicationRestrictedRelocation of microearthquake swarms in the Peloritani mountains – implications on the interpretation of seismotectonic patterns in NE Sicily, Italy(2005)
; ; ; ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Langer, H.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; The Peloritani Mountains in northeastern Sicily make part of the Appennine-Maghrebian Chain, which forms the highly deformed southern margin of the European Continent. In this zone the NW–SE-striking ‘Aeolian-Tindari-Giardini’ System (ATG) separates two areas of seismicity. To the west of the ATG fault system, seismic activity below a depth of 40 km is essentially absent. To the east of this fault system,we note a significant presence of intermediate depth and deep events, which mark the subduction zone in the Calabrian Arc. Between 1994 and 2003 300 microearthquakes could be located with fair accuracy near the ATG fault system. Their depths range from less than 5 to 40 km, with greater depths occurring to the east of the ATG.We examined the resolution capability of the standard location by applying a grid search location for typical events. The distribution of the residuals shows trends recognizable in the standard locations that are in part an artefact of a non-ideal conditions of the standard locations, such as the station configuration, the use of an unsuitable velocity model and inconsistencies of arrival time pickings. By applying relative location techniques (the double-difference method and a master-event technique) we were able to reduce the scatter of hypocentres significantly. We focused in particular on earthquake families with similar waveforms and estimated the geometrical extent of hypocentre clusters. Compared to the standard location the dispersion of hypocentres decreased by an amount of over 90 per cent and the volume occupied by the foci contracted to 1 per cent. The significance of these geometries was tested with Monte Carlo experiments and by interchanging the master events. The cluster geometries are consistent with the dislocation patterns as inferred from fault-plane solutions but do not show a simple relation to the ATG. The role of fluid flow of plutonic origin may be invoked as a possible trigger mechanism. This hypothesis is supported by the presence of geothermal anomalies in the vicinity as well as by an upward migration trend in foci.212 108 - PublicationOpen AccessThe December 2015 Mount Etna eruption: An analysis of inflation/deflation phases and faulting processes(2017-03-10)
; ; ; ; ; ; ; During the first days of December 2015, there were four paroxysmal events at the “Voragine” crater onMount Etna, which were among the most violent observed during the last two decades. A few days afterthe “Voragine” paroxysms, the Pernicana – Provenzana fault system, located near the crater area, under-went an intense seismic swarm with a maximum “local” magnitude MLof 3.6. This paper investigatesthe relationship between the eruptive phenomenon and the faulting process in terms of Coulomb stresschanges. The recorded seismicity is compatible with a multicausal stress redistribution inside the volcanoedifice, occurring after the four paroxysmal episodes that interrupted the usual trend of inflation observedat Mt. Etna. The recorded seismicity falls within the framework of a complex chain of various and inter-correlated processes that started with the inflation preparing the “Voragine” magmatic activity. This wasfollowed with the rapid deflation of the volcano edifice during the paroxysmal episodes. We determinedthat the recorded deflation was not the direct cause of the seismic swarm. In fact, the associated Coulombstress change, in the area of seismic swarm, was of about −1 [bar]. Instead, the fast deflation caused therarely observed inversion of dislocation in the eastern flank at the same time as intense hydrothermalactivity that, consequently, underwent an alteration. This process probably reduced the friction along thefault system. Then, the new phase of inflation, observed at the end of the magmatic activity, triggeredthe faulting processes.143 52 - PublicationOpen AccessEstimation of an optimum velocity model in the Calabro-Peloritan mountains – Assessment of the variance of model parameters and variability of earthquake locations(2007-09)
; ; ; ; ;Langer, H.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Raffaele, R.; Dip. di Scienze Geologiche, Università di Catania ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; Accurate earthquake locations are of primary importance when studying the seismicity of a given area, they allow important inferences on the ongoing seismo-tectonics. Both, for standard, as well as for earthquake relative location techniques, the velocity parameters are kept fixed to a-priori values, that are assumed to be correct, and the observed traveltime residuals are minimised by adjusting the hypocentral parameters. However, the use of an unsuitable velocity model, can introduce systematic errors in the hypocentre location. Precise hypocentre locations and error estimate, therefore, require the simultaneous solution of both velocity and hypocentral parameters. We perform a simultaneous inversion of both the velocity structure and the hypocentre location in NE-Sicily and SW-Calabria (Italy). Since the density of the network is not sufficient for the identification of the 3D structure with a resolution of interest here, we restrict ourselves to a 1D inversion using the well-known code VELEST. A main goal of the paper is the analysis of the stability of the inverted model parameters. For this purpose we carry out a series of tests concerning the initial guesses of the velocity structure and locations used in the inversion. We further assess the uncertainties which originate from the finiteness of the available datasets carrying out resampling experiments. From these tests we conclude that the data catalogue is sufficient to constrain the inversion. We note that the uncertainties of the inverted velocities increases with depth. On the other hand the inverted velocity structure depends decisively on the initial guess as they tend to maintain the overall shape of the starting model. In order to derive an improved starting model we derive a guess for the probable depth of the MOHO. For this purpose we exploit considerations of the depth distribution of earthquake foci and of the shear strength of rock depending on its rheological behaviour at depth. In a second step we derived a smooth starting model and repeated the inversion. Strong discontinuities tend to attract hypocentre locations which may introduce biases to the earthquake location. Using the smooth starting model we obtained again a rather smooth model as final solution which gave the best travel-time residuals among all models discussed in this paper. This poses severe questions as to the significance of velocity discontinuities inferred from rather vague a-priori information. Besides this, the use of those smooth models widely avoids the problems of hypocentre locations being affected by sudden velocity jumps, an effect which can be extremely disturbing in relative location procedures. The differences of the velocity structure obtained with different starting models is larger than those encountered during the bootstrap test. This underscores the importance of the choice of the initial guess. Fortunately the effects of the uncertainties discussed here on the final locations turned out as limited, i. e., less than 1 km for the horizontal coordinates and less than 2 km for the depth.304 194 - PublicationOpen AccessHYPSTHER PROJECT: HYBRID GROUND MOTION PREDICTION EQUATIONS FOR PSHA PURPOSES(2017-01-09)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In the last decades, the calibration of reliable GMPEs became a critical issue in Probabilistic Seismic Hazard Assessment (PSHA). NGA-East project provides a set of new GMPEs for median and standard deviation of Ground Motions (GMs) and their associated weights in the logic trees for use in PSHA for Central and Eastern North-American Region. These results include the use of synthetic data to fill the lacking of observations, especially for moderate to large earthquakes in near field conditions. On the European side, some efforts have been made within the NERA EU Project for the calibration of physics-based GMPEs, which are particularly effective in showing important ground motion features in near source regions. Indeed, when the site is very close to the fault, the rupture processes are predominant and the finite-source effects, such as directivity, hanging wall/foot wall, radiation-pattern and slip distribution can dominate the GMs. Therefore, the empirical GMPEs are generally incapable to capture such features, because the strong motion recorded data in near source are few. This paper explains the aims of HYPSTHER (HYbrid ground motion prediction equations for PSha purposes: the study case of souTHERn Italy) project, devoted to develop a methodological approach to retrieve ground motion prediction models, based on the integration between recorded and synthetic data. The motivation of this research is to supply the lack of instrumental observations for moderate to large earthquakes in near fault conditions. In this framework, we will test this methodology for the study case of Southern Italy, focusing our attention on Calabria and Sicily regions. The target area has been chosen based on the expected high hazard level, despite the seismic activity has been scarce in the last decades. In addition, along the Sicily coast many critical infrastructures are present, such as chemical plants and large ports, which strongly increase the risk of technological accidents induced by natural hazards. The results of the HYPSTHER project will be a set of Ground Motion Prediction Equations (GMPEs) for PGA, PGV and SA in the period range T=0.04-4s. Additional results include recorded and synthetic ground motion datasets. The project products can be tested and incorporated in a next generation of the Italian Seismic Hazard Maps.127 75 - PublicationOpen AccessPlanning the improvement of a seismic network for monitoring active volcanic areas: the experience on Mt. Etna(2013-10-23)
; ; ; ; ; ;D’Alessandro, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Di Prima, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Rapisarda, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980’s, seismic activity was monitored at Mt. Etna (volcano) by a permanent seismic network, progressively improved in the following years. This network has been considerably enhanced since 2005 by 24-bit digital stations equipped with broad-band (40s) sensors. Today, thanks to a configuration of 33 broad-band and 12 short-period stations, we have a good coverage of the volcanic area as well as a high quality of the collected data. In the framework of the VULCAMED project a workgroup of Istituto Nazionale di Geofisica e Vulcanologia has taken on the task of developing the seismic monitoring system, through the installation of other seismic stations. The choice of optimal sites must be clearly made through a careful analysis of the geometry of the existing seismic network. In this paper, we applied the Seismic Network Evaluation through Simulation in order to evaluate the performance of the Etna Seismic Network before and after the addition of the stations in the candidate sites. The main advantage of the adopted method is that we can evaluate the improvement of the network before the actual installation of the stations. Our analysis has permitted to identify some critical issues of the current permanent seismic network related to the lack of stations in the southern sector of the volcano, which is nevertheless affected by a number of seismogenic structures. We have showed that the addition of stations at the candidate sites would greatly extend the coverage of the network to the south by significantly reducing the errors in the hypocenter parameters estimation.548 119 - PublicationOpen AccessContributo delle reti sismiche mobili durante i periodi di crisi: l’esempio della sequenza dei Monti Nebrodi del 2011(2014-10-17)
; ; ; ; ; ; ; ;Cammarata, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Gambino, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Maiolino, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Messina, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Rapisarda, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Zuccarello, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; In questo lavoro viene descritta l’installazione di una rete mobile nell’area dei Monti Nebrodi in seguito all’evento del 23-06-2011 di Ml = 4.6 e come tale intervento ha contribuito al miglioramento della localizzazione delle sorgenti sismiche soprattutto nella determinazione della profondità degli eventi. Verranno anche presentati i risultati delle localizzazioni ottenute attraverso l’integrazione dei dati acquisiti durante questa campagna, con quelli della rete sismica permanente dell’INGV-Osservatorio Etneo ( INGV -OE).678 102 - PublicationRestrictedPossible role of fluid overpressure in the generation of earthquake swarms in active tectonic areas: The case of the Peloritani Mts. (Sicily, Italy)(2008)
; ; ; ; ; ;Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Palano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Sortino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; ; ; ; The Peloritani Mts. (NE Sicily) are characterized by frequent seismicity. Between 1994 and 2006 more than 1000 earthquakes (1.0≤ML≤3.3) occurred, mostly as highly clustered swarms located at shallow depth near the villages of Castroreale and Rodì Milici (western part of Peloritani Mts.). The same area is also characterized by some geothermal springs and gas vents. Using a multidisciplinary approach, data were collected on the tectonic setting, seismicity pattern and geochemical characteristics of fluid emissions, with the aim of understanding the process of earthquake swarm generation beneath the investigated area. Most of the gases emitted in the study area, in terms of focused and/or diffuse gas emissions often associated with thermal fluids, is of mantle origin, as shown by their He isotopes ratio. On approaching the surface, deep gases interact strongly with local aquifers. An estimate of both the surface efflux of mantle-derived gases measured in focused emissions and of the P–T conditions of fluids in the local crust point to a pressurised gas source that would be located at depth of 7–12 km, corresponding to the range of hypocentral depths of seismic swarms. The complex network of tectonic structures in the area would act as high-permeability pathways for the migration of sub-crustal fluids towards the surface. This scenario could be compatible with a close interplay between pressurised mantle fluids at depth, nucleation of earthquakes due to higher-thanhydrostatic pore pressure and release of mantle-derived gases at the surface. This sequence would be repeated in time, thus producing the observed cycles in the local seismic activity.294 36 - PublicationOpen AccessMultidisciplinary study of the Tindari Fault (Sicily, Italy) separating ongoing contractional and extensional compartments along the active Africa–Eurasia convergent boundary(2013)
; ; ; ; ; ; ;De Guidi, G.; Dipartimento di Scienze Geologiche, Università di Catania, Catania, Italy ;Lanzafame, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Palano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Puglisi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scaltrito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Scarfì, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; The Africa–Eurasia convergence in Sicily and southern Calabria is currently expressed by two different tectonic and geodynamic domains: thewestern region, governed by a roughlyN–S compression generated by a continental collision; the eastern one, controlled by a NW–SE extension related to the south-east-directed expansion of the Calabro–Peloritan Arc. The different deformation pattern of these two domains is accommodated by a right-lateral shear zone (Aeolian–Tindari–Letojanni fault system) which, from the Ionian Sea, north of Mt. Etna, extends across the Peloritani chain to the Aeolian Islands. In this work, we study the evidence of active tectonics characterizing this shear zone, through the analysis of seismic and geodetic data acquired by the INGV networks in the last 15 years. The study is completed by structural and morphological surveys carried out between Capo Tindari and the watershed of the chain. The results allowed defining a clear structural picture depicting the tectonic interferences between the two different geodynamic domains. The results indicate that, besides the regional ~N130°E horizontal extensional stress field, another one, NE–SW-oriented, is active in the investigated area. Both tension axes are mutually independent and have been active up to the present at different times. The coexistence of these different active horizontal extensions is the result of complex interactions between several induced stresses: 1) the regional extension (NW–SE) related to the slab rollback and back-arc extension; 2) the strong uplift of the chain; 3) the accommodation between compressional and extensional tectonic regimes along the Aeolian– Tindari–Letojanni faults, through a SSE–NNW right-lateral transtensional displacement. In these conditions, the greater and recurring uplift activity is not able to induce a radial extensional dynamics, but, under the “directing” action of the shear system, it can only act on the regional extension (NW–SE) and produce the second system of extension (NE–SW).252 530
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