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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 AccessSeismicity, seismotectonics and crustal velocity structure of the Messina Strait (Italy)(2009-11)
; ; ; ;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 Messina Strait is the most important structural element interrupting the southernmost part of the Alpine-Apenninic orogenic belt, known as the Calabro-Peloritan Arc. It is being a narrow fan-shaped basin linking the Ionian Sea to the Tyrrhenian Sea. This region is affected by considerable seismic activity which mirrors the geodynamic processes due to the convergence between the African and the Eurasian plates. In the last four centuries, a significant number of disastrous earthquakes originated along the Arc. Among these, the most noteworthy event occurred on December 28, 1908 (known as the Reggio Calabria-Messina earthquake), in the Messina Strait area and caused a large tsunami and more than 100,000 casualties. In this research we focus on the relationships between the general tectonic setting, which characterize the Messina Strait and adjacent areas, seismicity patterns and the crustal structure. We analyzed a data set consisting of more than 300 events occurring in the years from 1999 to 2007, having a magnitude range from 1.0 to 3.8. This data set was exploited in a local earthquake tomography, by carrying out a simultaneous inversion of both the three-dimensional velocity structure and the distribution of seismic foci. We applied the “tomoADD” algorithm, which uses a combination of absolute and differential arrival times and a concept of self-adapting grid geometry, accounting for ray density encountered across the volume. With this method the accuracy of event locations is improved and velocity structure near the source region is resolved in more detail than standard tomography. Fault plane solutions were obtained for the major and best-recorded earthquakes. The obtained velocity images highlight vertical and lateral heterogeneities that can be associated with structural features striking from NNE-SSW to NE-SW. These results are consistent with important tectonic elements visible at the surface and the pattern delineated by earthquake locations and focal mechanisms.302 432 - 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 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 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 - PublicationOpen AccessRoutine analysis for seismic monitoring of eastern Sicily (Italy)(2009-06-11)
; ; ; ; ; ; ; ; ; ; ;Alparone, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Barberi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Di Grazia, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Giampiccolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Maiolino, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Mostaccio, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Musumeci, C.; 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 ;Ursino, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; ; ; ; Eastern Sicily is one of the most high seismic and volcanic risk areas in Italy. The systematic monitoring of seismic activity in this region is carried out by means of a permanent local network, managed by the Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Catania (INGV-CT). The monitoring is performed: on-line by means of automatic systems designed to detect and elaborate the earthquakes and volcanic tremor, while off-line thanks to an expert scientific staff. Skilled ”analysts” daily recognize, analyse and storage all seismic events which occur in the Eastern Sicily, providing accurate information on the time evolution of earthquake activity recorded within the seismic network. In particular, the studied area encompasses four different geodynamic domines: two volcanic areas (Etna, Aeolian Island) and two tectonic ones (Hyblean Plateau and Peloritain Mountains). The good quality of earthquakes locations, the precise and the careful storage of the data, are a fundamental basis for further and important seismological studies. In detail, the scientific staff carry out, with high precision and regularity, the following main tasks: - daily counting of the earthquakes that is possible to recognize on seismograms of continuous recordings; calculation of the duration magnitude and the cumulative seismic strain release; - earthquakes location by using Winsuds software to calculate the main hypocentral parameters stored in catalogues that can be consulted in http://www.ct.ingv.it/Sismologia/analisti/default.asp - calculation of local magnitude for all the localized earthquakes with Matlab code; - waveforms, P and S-wave readings polarities and Hypoellipse output files are stored in appropriate directories inside a Databank; the Database mainly contains the “local” events recorded within the areas of coverage and some events recorded outside the network but in adjoining areas (e.g. southern Calabria, Ionian Sea, Thyrrenian Sea); - information on the daily number of explosion-quakes, VLP and landslides recorded at Stromboli volcano and on the number of very local earthquakes recorded in proximity of La Fossa of Vulcano island; - computation of focal plane solutions using the FPFIT algorithm with the aim to evaluate nodal planes and orientation of P and T axes for earthquakes with Md 3.0. Moreover, during the main eruptive events the scientific staff, in order to alert regional and national Civil Protection authorities, furnish a detailed analysis of seismic activity (parameters of earthquake locations, epicentral maps and cross sections, focal mechanisms, seismic strain release, earthquake rate, etc…) in real time or near real time.259 97 - 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 - 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 - 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 - 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 - PublicationRestrictedSeismological constraints on the Mt. Etna (Italy) 2018 flank eruption and implications in the volcano flanks dynamics.(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 3D earthquake locations, focal mechanisms and stress tensor distribution in a 16- month interval covering the 2018 Mt. Etna flank eruption, enabled us to investigate the relationship between magma intrusion and structural response of the volcano and shed light on the dynamic processes affecting the instability of Mt. Etna. The magma intrusion likely caused tension in the flanks of the volcano, leading to significant ground deformation and redistribution of stress on the neighbouring faults at the edge of Mt. Etna's unstable sector, encouraging the ESE sliding of the eastern flank of the volcano. Accordingly, FPSs of the post-eruptive events show strike slip faulting mechanisms, under a stress regime characterized by a maximum compressive σ1, NE-SW oriented. In this perspective, any flank eruption could temporarily enhance the sliding process of both the southern and eastern flanks of the volcano.911 7
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