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  • 1
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    Seismological constraints on the intrusive mechanism leading the 2001 Etna eruption (2012)
    INGV
    Details
    Publication Date: 2012-02-03
    Description: The 2001 Etna eruption occurred from July 17th to August 9th, 2001 and was preceded by several days of intense seismicity and ground deformation. We investigated the seismic activity recorded during November 2000 - June 2001 interval time preceding the eruption, to understand the meaning of the seismicity connected to the dike intrusion, that locally modified the stress field acting in the area. The earthquakes were recorded by the permanent local networks operating during that time and run by the Istituto Internazionale di Vulcanologia (IIV-CNR) and the Sistema POSEIDON. During the analyzed period, 683 earthquakes have been firstly localized by means of a 1D velocity model derived from Hirn et al., 1991 using the software HypoEllipse [Lahr, U. S. Geol. Survey, Open-File Report, 89/116, 81 pp., 1989]. In order to further improve the quality of the seismic dataset, we extracted 522 earthquakes with Gap less than 200°, Erh 〈 1.5 km, Erz 〈 2 km, RMS less than 0.5 sec, and a minimum number of S phases equal to 2. This latter seismic dataset was relocated using TomoDD code [Zhang and Thurber, BSSA, 93, 1875-1889. 2003] and a 3D velocity model [Patanè et al., Science, 313, 821- 823, 2006 after modified]. Using first motion polarity data, 3D fault plane solutions were computed by means of the software FPFIT [Reasenberg and Oppenheimer, U.S. Geological Survey Open File Report, 85/739, 109 pp, 1985]. Then, adopting restricted selection criteria (Npol more than 12; focal plane uncertainties less than 20°; number of solutions 〈 2; number of discrepancies less than 15%), we selected 116 FPSs. This dataset represented the input file for the stress and strain tensors computation using the inversion codes developed by Gephart and Forsyth,[ JGR 89: 9305-9320, 1984] and by Kostrov [Izv Acad Sci USSR Phys Solid Earth, 1, 23-40], respectively. On the basis of P and T axes distribution and the orientation of the main seismogenic stress and strain axes, we put some seismological constraints on the recharging phase leading to the 2001 Etna eruption.
    Description: Published
    Description: Salina
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: open
    Keywords: Etna ; stress ; strain ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 2
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    Tomographic images and analysis of stress and strain tensors at Mt. Etna: the magmatic unrest leading to the 2008 Etna eruption (2009)
    Details
    Publication Date: 2017-04-04
    Description: We analysed the seismic activity preceding and accompanying the onset of the 2008 Mt. Etna eruption. Since January 2008, a clear seismic evidence of a magmatic unrest of the volcano was observed. Seismicity was firstly located in the southwestern sector of the volcano, at depth ranging between 10 and 20 km, along two tectonic structures (NE-SW and NNW-SSE) usually associated with deeper magmatic recharge mechanisms (Figs. 1, 2). Afterwards, the seismicity was located along the shallower portions of the main structures of the northeastern and southern flanks of the volcano (Figs. 1, 2). On May 13, 2008 an intense seismic swarm (about 230 events in 7 hours) announced the beginning of the eruption (Fig. 1, white circles). In order to provide seismological constraints to the magmatic unrest of the volcano, 336 earthquakes recorded from January 2007 to May 2008 (magnitude greater than 1.0) were selected for stress and strain tensors computation and 3D velocity and attenuation structure determination. This in order to individuate possible stress variations caused by the activation of magmatic sources which can be well evidenced by 3D tomographic images.
    Description: Published
    Description: Rome
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: Mt. Etna ; Tomography ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 3
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    Volcanological inferences from seismic-strain tensor computations at Mt. Etna Volcano, Sicily (2008)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Kostrov's (1974) algorithm for seismic-strain tensor computations, in the version implemented by Wyss et al. (1992a) for error estimates, has been applied to shear-type earthquakes occurring beneath the Etna volcano during 1990-1996. Space-time variations of strain orientations and amplitudes have been examined jointly with ground-deformation and gravimetric data collected in the same period and reported in the literature. Taking also into account the information available from volcanological observations and structural geology, we propose a model assuming that hydraulic pressure by magma emplaced in nearly north-south vertical structures produces the E-W orientation of the maximum compressive strain found in the upper 10 km beneath the crater area. In contrast, regional tectonics deriving from the slow, north-south convergence between the African and European plates appear to play a dominant role in the generation of stress and strain fields at crustal depths deeper than 10 km below the volcano. According to our interpretation, the progressive ascent of magma through the upper crust prior to eruption produces the observed gravity changes, cone inflation and unusual seismic strain rate in the upper 10 km associated with a more sharply defined seismic deformation regime (i.e. very small confidence limits of the epsilon 1 orientation). In agreement with this model, deflation revealed by ground-deformation data during the course of the major 1991-1993 eruption was accompanied by a practically nil level of shallow seismicity.
    Description: Published
    Description: 318-330
    Description: JCR Journal
    Description: open
    Keywords: Mt. Etna ; Italy ; Earthquakes ; Seismic strain ; Stress inversion ; Volcanic processes ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Tomographic images of a low velocity Vp and Vs volume beneath Stromboli Volcano, Italy (2009)
    Details
    Publication Date: 2017-04-04
    Description: The present study is mainly focused to determine the hypocentral locations and the velocity structure between the northeastern Sicily and southern Calabria, including the Aeolian Archipelago with particular regard to Stromboli volcano. The main goals are: i) to explore the differences between relative and absolute earthquake locations, ii) to identify spatial clusters in the seismicity, in order to investigate on the most active seismogenic zones and structures and iii) to recognize the presence of low velocity regions beneath the Aeolian Archipelago related to the presence of partial melting. We applied the TomoDD algorithm which use both absolute and differential arrival times to simultaneously determine event locations and Vp and Vp/Vs velocity models. 1,304 well located events have been considered during the 1994-2006 period. This code was applied to the catalog phase data, combining 11,261 P-wave and 5,751 S-wave arrival time differences. On the basis of the distribution of the events, a denser grid with respect to previous studies was used. This allowed a higher resolution of the velocity model and to find a better correspondence with the most active seismogenic zones and structures. Moreover, being the velocity structure of Stromboli poorly defined, a particular attention was devoted to this area. Tomographic images beneath this volcano revealed the presence of a low Vp and Vs (average values around 5.4 and 3.1 Km/s, respectively) elongated volume in the crust, suggesting the existence of partial melting. This volume extending until 17 km of depth, overlies a high Vp and Vs (values greater than 7.5 and 4.5 km /s, respectively) region that can be related to the Moho.
    Description: Published
    Description: Reykjavik
    Description: open
    Keywords: Tomography ; Stromboli ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 5
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    Analysis of the recharging of the volcanic feeder at Mt. Etna using pattern classification of volcanic tremor data and comparison with recent seismic tomography (2012)
    Details
    Publication Date: 2017-04-04
    Description: ABSTRACT FINAL ID: V41H-06 TITLE: Analysis of the recharging of the volcanic feeder at Mt. Etna using pattern classification of volcanic tremor data and comparison with recent seismic tomography SESSION TYPE: Oral SESSION TITLE: V41H. Surveillance of Volcanic Unrest: New Developments in Multidisciplinary Monitoring Methods I (Video On-Demand) Susanna M R Falsaperla1, Graziella Barberi1, Ornella Cocina1 INSTITUTIONS (ALL): 1. Sez Catania, INGV, Catania, Italy. KKAnalysis is a method of pattern classification based on Self Organizing Maps and Fuzzy Cluster Analysis successfully applied to volcanic tremor data recorded at Mt. Etna [Langer et al., J. Volcan. Geoth. Res., doi:10.1016/j.jvolgeores.2010.11.019, 2010]. The classifier can detect anomalies in the seismic signal long before changes in volcanic tremor amplitude and spectral content become evident, and is particularly useful in highlighting impending paroxysmal eruptive activity, such as lava fountains and intense effusive activity. In this study we propose an application to volcanic tremor data recorded from November 1 2005 to January 31 2006, when strong changes in amplitude and frequency content were detected without any visible activity of the volcano was reported by volcanologists and alpine guides. The classifier detects patterns that we interpret as evidence of recharging of the volcanic feeder at depth. We discuss our results considering stations of the permanent network of Mt. Etna, which is run by INGV, comparing their characteristics resulting from pattern classification. To corroborate our results we also take into account VT seismicity and a recently published seismic tomography, which allows us to look at discontinuities and possible zone of magma transfer at depth.
    Description: Published
    Description: San Francisco, California, USA
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: open
    Keywords: Seismic data ; Etna ; volcanic tremor ; tomography ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 6
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    Dynamics of the upper SE flank of Mt. Etna: a synoptic view from the characteristics of the seismic signals between November 2005 and January 2006 (2012)
    Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Osservatorio Etneo
    Details
    Publication Date: 2017-04-04
    Description: Dynamics of the upper SE flank of Mt. Etna: a synoptic view from the characteristics of the seismic signals between November 2005 and January 2006 Falsaperla, S., G. Barberi, O. Cocina Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Osservatorio Etneo,P.zza Roma 2, 95125, Catania, Italy The July – December 2006 eruptive activity at Mt. Etna was preceded by changes in volcanic tremor characteristics. The amplitude of volcanic tremor peaked in December 2005 after a restless, even though slow increase, starting from July 2005, during which no visible change was reported in the visible activity of the volcano by volcanologists and alpine guides. In this study we focus on a three-month long time period, i.e., from November 1 2005 to January 31 2006, which was characterized by strong changes in amplitude and frequency content of volcanic tremor. In so doing, we analyze records from permanent stations run by INGV as well as a few broadband seismic sensors of a temporary array, deployed from July 2005 to January 2006. Pattern classification analysis based on Self Organizing Maps and Fuzzy Cluster Analysis highlights variations in volcanic tremor data we interpret as evidence for magma ascent, representing a stage of recharging of the volcanic feeder at depth. This hypothesis is supported by VT seismicity, which was intense in the time span investigated. In particular, earthquakes recorded on January 8, 2006 (with foci between 10 and 15 km) were the major indicators to sketch out the modality of transfer of magma within the volcano during this recharging phase [Cocina et al., Geophysical Research Abstracts, Vol. 12, EGU2010-9267, 2010]. Finally, differences in the characteristics of the seismic signal at reference stations are also analyzed in the light of a recently published seismic tomography [Patanè et al., Science, Vol. 313, 821-823, 2006].
    Description: Published
    Description: Salina, Italy
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: open
    Keywords: Etna ; seismic signals ; pattern classification ; tomography ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 7
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    Time-resolved velocity tomography at Mount Etna (Italy) volcano during 2000-2008 (2012)
    Details
    Publication Date: 2017-04-04
    Description: The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography (4D tomography) to detect variations in elastic parameters during different volcanic cycles in the period November 2000–May 2008, that includes several flank eruptions. The use of a large number of permanent seismic stations and the abundance of local earthquakes, occurring both before and during the eruptions, guarantee consistent and high-resolution velocity models. First, we performed a tomographic inversion of the whole data set to define the 3D P-wave velocity (VP) and the structure of the P- to S-wave velocity ratio (VP/VS). A total of ca. 3,000 well constrained earthquakes (root mean square time residuals ≤ 0.4 s; horizontal and vertical hypocentral location errors ≤ 1.5 km; azimuthal gap of the stations ≤ 180°), ca. 40,000 P-wave arrivals, and ca. 9,000 S-wave arrivals were inverted to model a grid, 2 km by 2 km by 1 km spaced, with the use of SIMULPS-14 software. Then, on the basis of geophysical and geochemical observations indicating some cyclic recharging and discharging (eruptions) phases, we inverted different sub-periods to investigate time variations in the elastic parameters. The observed time changes of velocity-oriented anomalies suggest that four-dimensional tomography could provide a basis for more efficient volcano monitoring and short- and midterm eruption forecasting.
    Description: Published
    Description: San Diego (California)
    Description: restricted
    Keywords: Mt. Etna ; Tomography
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 8
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    Seismological features of the Pernicana–Provenzana Fault System (Mt. Etna, Italy) and implications for the dynamics of northeastern flank of the volcano (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: The Pernicana–Provenzana Fault System is one of the most active tectonic systems of Mt. Etna and it plays an important role in the dynamic of the eastern flank of the volcano. Earthquakes occurring close to this structural trend have reached magnitudes up to 4.2, sometimes with coseismic surface faulting, and have caused severe damages to tourist resorts and villages in the vicinity of this structure. In the last decade, a large number of shocks, sometimes in the form of swarms, linked to Pernicana–Provenzana Fault System movements have been detected by the permanent local seismic network operating in eastern Sicily. In this paper, we report on the detailed study of the seismic activity occurring during the 2000–2009 time span in the Pernicana–Provenzana Fault System area. Firstly, we located 407 earthquakes using a standard location code and a 1D crustal velocity model. We then applied two different approaches to calculate precise hypocenter locations of the events. In particular, a non-linear code was adopted to obtain an estimate of the a posteriori Probability Density Function in 3D space for the hypocenter location. Moreover, a relative location of correlated event pairs was performed, using the double-difference method. These two different location approaches allowed defining with good accuracy, the most active and hazarding sectors of the structure. The results of these precise locations showed a tighter clustering in the epicenters and in focal depths, in comparison with standard locations. Earthquakes are located along the Pernicana–Provenzana Fault System, and are mainly clustered in two zones, separated by an area with very low rate of earthquakes occurrence, but characterized by the highest energy release. Depths of the foci are very shallow, ranging between the surface and about 3 km b.s.l. Kinematics of the Pernicana–Provenzana Fault System, revealed by the fault plane solutions computed for the most energetic earthquakes, highlights a predominant dip–slip and left strike movements along E–W oriented fault planes, in agreement with field observations.
    Description: Published
    Description: 16-26
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Etna volcano ; Pernicana–Provenzana Fault System ; Earthquakes ; Precise location ; Fault plane solutions ; Seismic strain release ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Time-resolved velocity tomography at Mount Etna (Italy) volcano during 2000-2008 (2012)
    Details
    Publication Date: 2017-04-04
    Description: The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography (4D tomography) to detect variations in elastic parameters during different volcanic cycles in the period November 2000–May 2008, that includes several flank eruptions. The use of a large number of permanent seismic stations and the abundance of local earthquakes, occurring both before and during the eruptions, guarantee consistent and high-resolution velocity models. First, we performed a tomographic inversion of the whole data set to define the 3D P-wave velocity (VP) and the structure of the P- to S-wave velocity ratio (VP/VS). A total of ca. 3,000 well constrained earthquakes (root mean square time residuals 0.4 s; horizontal and vertical hypocentral location errors 1.5 km; azimuthal gap of the stations 180 ), ca. 40,000 P-wave arrivals, and ca. 9,000 S-wave arrivals were inverted to model a grid, 2 km by 2 km by 1 km spaced, with the use of SIMULPS-14 software. Then, on the basis of geophysical and geochemical observations indicating some cyclic recharging and discharging (eruptions) phases, we inverted different sub-periods to investigate time variations in the elastic parameters. The observed time changes of velocity-oriented anomalies suggest that four-dimensional tomography could provide a basis for more efficient volcano monitoring and short- and midterm eruption forecasting.
    Description: Published
    Description: Vienna
    Description: restricted
    Keywords: Mt. Etna ; Tomography
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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