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  • 1
    Publication Date: 2017-04-04
    Description: On April 5, 2003, one of the largest eruptions in the last decades was observed at Stromboli volcano, Italy. The eruption occurred in a period of increased volcanic activity, following a first explosion in December 2002, which interrupted the typical moderate “Strombolian” behaviour. We present an exhaustive analysis of the available broadband seismic data and relate them to the observed eruption phases. Prominent features of the seismic signals include an ultra long period signal starting a few tens of seconds prior to the explosive eruption as well as a strong energetic signal a few seconds after the onset of the eruption. Both signals are not exactly synchronized with the other geophysical observations. We present a detailed study of those signals using spectral and particle motion techniques. We estimate eruption parameters and seismic source characteristics by different inversion approaches. Results clearly indicate that the paroxysmal eruption was triggered by a shallow slow thrust-faulting dislocation event with a moment magnitude of Mw=3.0 and possibly associated with a crack that formed previously by dike extrusion. At least one blow-out phase during the paroxysmal explosion could be identified from seismic signals with an equivalent moment magnitude of Mw=3.7 and is represented by a vertical linear vector dipole and two weaker horizontal linear dipoles in opposite direction, plus a vertical force.
    Description: Published
    Description: 164-178
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Stromboli ; source inversion ; volcano seismology ; paroxysm ; 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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  • 2
    Publication Date: 2017-04-03
    Description: Source inversion for long period (LP) events in volcanic areas is an ongoing research topic. The high interest of volcanologists to understand the physical phenomena which govern these characteristic events is related to the fact that they may be directly generated by uid transfers and some of them could be candidates for volcanic activity parameters, or precursors of volcanic eruptions. The signal class of LP-type events generally includes di erent volcanic transients with dominant frequencies in the range between 0.5 and 5 Hz. Although some source models have been proposed to explain their generation (vibration of uid- lled cavities, etc.), the large variety of LP signal forms and the existence of alternative models to explain some of the observations, make it interesting to develop new inversion schemes. Our main goal is to propose an inversion methodology to determine LP source mechanisms and study these events through an exhaustive source inversion by using synthetic data.
    Description: Published
    Description: Bremen (Germany)
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: source inversion ; volcano ; 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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  • 3
    Publication Date: 2017-04-04
    Description: Abstract: On April 5, 2003, one of the largest eruptions in the last decades was observed at Stromboli volcano, Italy. The eruption occurred in a period of anomalous volcanic activity, after a previous explosion in December 2002 interrupted the typical moderate "Strombolian" behaviour. An exhaustive analysis of the available broadband seismic data is here presented and related to the observed eruption phases. Prominent features of the seismic signals include a very long period signal a few tens of seconds prior to the explosive eruption, as well as a strong energetic signal a few seconds after the onset of the eruption.
    Description: Published
    Description: San Francisco
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: source inversion ; Stromboli ; volcano seismology ; paroxysm ; 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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  • 4
    Publication Date: 2017-04-04
    Description: The Northern Apennines (NA) were predominantly formed by a Meso-Cenozoic sedimentary sequence thrust northeast and stacked over the Adriatic foreland during Late Miocene-Pleistocene. Extension on the Tyrrhenian margin is synchronous with thrust emplacements along the external Apenninic chain and is associated by crustal thinning, normal faulting, ductile deformation, volcanic activity and high heat flow. Both, the extensional and the compressional fronts migrated towards the Adriatic foreland during the Plio-Pleistocene. Crustal extension everywere disrupted structural architectures formed during the preceding compressional phase leading to the development of thinned, uplifted and extended crust in the Tuscany mainland. Several models have been proposed to explain the evolution of the NA that are acknowledged to be tectonically complex. We present results from a Receiver Functions (RFs) analysis of teleseismic events recorded at Arezzo seismic station (Tuscany). A broad-band station (ARZ) is installed on the north-east margin of the “Val di Chiana” extensional syntectonic basin. We selected and grouped in “bins” high signal/noise teleseismic events of four years of recording to compute a data-set of RFs. We applied a classical inversion scheme (a Neighbourhood Algorithm) and we carried out a three-dimensional modelling. As a criterion to identify and to distinguish the effects of azimuthal anisotropy from those of lateral heterogeneity, we included the harmonic angular analysis performed by stacking Radial (R) and Transverse (T) components with weights depending on the backazimuth. The results of these analysis provide a detailed three-dimensional image of the S-velocity lithosphere structure.
    Description: Unpublished
    Description: Vienna
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: receiver function ; Northern Apennines ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 5
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    American Geophysical Union
    Publication Date: 2017-04-04
    Description: Explosion-quake seismograms recorded at Stromboli show that seismic phases with a high-amplitude and high-frequency content propagate with a velocity of approximately 330 m/s - the sound speed. The analysis of seismograms, recorded at a distance of 500 m from one of the three active vents, shows for the first onset a low frequency and particle motion characteristics of a p-wave, which loses its longitudinal polarization with the onset of the air-wave. Recording the explosion-quake simultaneously with a microphonewe would ascertain that the high frequency onset coincides with the air-wave's. In order to better understand the seismic wavefield generated by the atmospheric pressure, we performed a controlled source experiment at Stromboli using a seismic gun. Seismograms with the same two phases and particle motions comparable with the volcanic seismic data were obtained. A second experiment demonstrated, that the air-wave propagates at least in the uppermost 1m of the gound. We suggest that the seismic source of the corresponding seismograms is an explosion at the top of the magma column and conclude that the p- and air-waves are both generated in the same point and at the same time.
    Description: Published
    Description: 65-68
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: volcano seismology ; Stromboli ; air wave ; 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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  • 6
    Publication Date: 2017-04-04
    Description: In this paper we present the seismicity analysis of a small sector of the Northern Apennines in 27 terms of spatio-temporal distribution, merging data from the Italian seismic bulletin with new 28 data collected by temporal seismic networks. Our attention is focused on the region enclosed 29 between Toscana, Umbria, Marche and Emilia-Romagna. This area is mainly characterized by a 30 diffuse seismicity, partly clustered in small sequences (Mw 〈 4.7). Improved seismicity locations, 31 together with stress field analysis allows to characterize the manner of seismogenic stress release 32 in the area. Two regions of significantly different seismic release behavior could be 33 distinguished: (i) the inner/western part (Tuscan side) of the study area, where seismicity is 34 clustered at shallow depths (〈18 km) and where strong earthquakes occurred in the past, (ii) the 35 outer(eastern) part (Marche side), where the seismicity is diffuse across all of the crustal volume, 36 reaching depths of down to 30 km. 37 Along the Apenninic chain, seismicity is nearly absent inside well defined zones. In our opinion, 38 these peculiarities of seismicity release could be related to the heterogeneity of crustal volume 39 and to the transition between Tyrrhenian and Adriatic domains.
    Description: Submitted
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: Alto Tiberina Fault ; Seismicity ; Northern Apennines ; focal mechanisms ; stress field ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
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  • 7
    Publication Date: 2017-04-04
    Description: We analyze the seismicity of a small sector of the Northern Apennines merging data from the Italian seismic bulletin with original data collected by temporary seismic networks. Our attention is focused on the region enclosed between the Apenninic watershed and the Adriatic Sea. This portion of belt is interested by the occurrence of diffuse crustal seismicity and small-to-moderate earthquakes. In this paper we study the five small sequences with mainshock having Mw 〈 4.7 that in the past 15 years hit the area. Our interest is addressed to better understand the relationship between these events and the regional seismotectonic setting in terms of seismicity distribution and stress field. Two regions with different behavior in the seismic release can be distinguished: (i) along the watershed where seismicity is clustered at shallow depths (〈 15 km) and where strong earthquakes occurred in the past, (ii) an eastern portion where the seismicity is distributed across all of the crustal volume, locally reaching depths down to 30 km. The focal mechanism of the seismic sequences shows mainly normal fault kinematics coherent with the regional stress field. Detailed stress field analysis suggests a rotation of the principal stress axis moving from the axial part of the chain toward the Adriatic Sea to the east.
    Description: Published
    Description: 136-144
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Northern Apennines ; Stress field ; Focal mechanisms ; Seismicity ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 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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  • 8
    Publication Date: 2017-04-04
    Description: L’Appennino Settentrionale è una catena montuosa NE-vergente ed è il risultato dell’affioramento del prisma di accrezione originato in seguito alla subduzione della litosfera adriatica sotto il mar Tirreno ed ancora in atto (Faccenna et al., 2001). Dall’Oligocene ad oggi, l’Appennino Settentrionale è stato interessato da due fasi deformative: inizialmente compressiva con la formazione di thrusts e più recentemente distensiva (Elter et al., 1975). Attualmente è caratterizzato da un regime crostale distensivo con una velocità stimata circa 2.5 mm/anno (Hunstad et al., 2003). Gli effetti e le conseguenze di questi episodi deformativi sono ben visibili attraverso un’analisi geologica e geofisica. L’area in studio è posta in corrispondenza della transizione tra la successione Toscana ed il settore Tirrenico del dominio Umbro-Marchigiano, quindi, una zona particolarmente dibattuta da un punto di vista geodinamico, a causa della presenza di diverse tipologie crostali, flusso di calore e anomalie gravimetriche.
    Description: Published
    Description: Rome
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: receiver function ; Northern Apennines ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 9
    Publication Date: 2017-04-04
    Description: The high interest of volcanologists to understand the physical phenomena which governs long period (LP) events is related to the fact that they may be directly generated by fluid transfer and could be indicators of the level of activity in the volcano and in some cases could act as precursor to eruptions. The wide variety of waveforms and spectral contents existing for LP events, as well as the existence of alternative models to explain the observations make it interesting to develop new inversion schemes. We propose an inversion methodology to determine source mechanisms and study these events through an exhaustive source inversion by using synthetic and observed data. Our method for source inversion is based on a frequency domain approach, which has its main advantage in reducing computational requirements. The resulting source mechanism is represented by the sum of two time-dependent terms: a full moment tensor and a single force. The method has been applied to different sets of synthetic and observed data, including data from Kilauea volcano. Green’s functions have been calculated using different layered crustal models, which have been proposed for volcanic areas. Inversion tests are established to check the stability of the method and the possibility of retrieving all source components. The method has been finally applied to volcanic data and results are interpreted in terms of possible source models.
    Description: Published
    Description: Vienna
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: source inversion ; volcano ; 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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  • 10
    Publication Date: 2017-04-04
    Description: The steep topography, which characterizes certain volcanic areas, may strongly influence the displacement field associated to seismic signals. As a consequence, the interpretation of seismic data for the inversion of the seismic source and the crustal structure properties should carefully take into account these effects. We propose a set of numerical simulations for seismic wave propagation in a 3-D homogeneous model of Stromboli volcano, Italy, based on the application of a pseudospectral technique. The model assumes a topography with a discretization of 100 m on the horizontal directions, and 1 m on the vertical direction, while bathymetry is not yet included. We estimate the surface displacement field for different seismic sources, reproducing possible phenomena occurring during an eruptive process. These include purely isotropic sources, the realistic inclusion of an additional deviatoric CLVD component, which may take into account the effects of explosive events in presence of conduits and the final fall-out of material at the volcanic surface. Different durations of the source time function are tested in order to compare the effects of topography for seismic radiations with a variable range of frequency content. The comparison of results highlights the effects, which are strictly related to the presence of a steep topography.
    Description: Published
    Description: Vienna
    Description: 3.6. Fisica del vulcanismo
    Description: open
    Keywords: Stromboli ; source inversion ; 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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