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  • 1
    Article
    Article
    Recent activity of Nisyros volcano (Greece) inferred from structural, geochemical and seismological data, (2005)
    Associated volumes
    Details Availability
    In: Bulletin of volcanology, Berlin : Springer, 1986, 67(2005), Seite 358-369, 0258-8900
    In: volume:67
    In: year:2005
    In: pages:358-369
    Type of Medium: Article
    ISSN: 0258-8900
    Language: English
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  • 2
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    Joint observation of coherent coda waves at surface and underground arrays (2013)
    Oxford University Press
    Details
    Publication Date: 2013-06-11
    Description: Local and regional seismicity jointly recorded by two dense small aperture arrays, one installed at surface and one at 1.3 km depth, constitutes an interesting data set useful for coda observations. Applying array techniques to earthquakes recorded at the two arrays we measure slowness, backazimuth and correlation coefficient of the coherent coda wave signals in five frequency bands in the range 1–10 Hz. Slowness distributions show marked differences between surface and underground, with slow signals at surface (slowness greater than 1.0 s km –1 ) that are not observed underground. We interpret these coherent signals as surface waves produced by the interaction of body waves with the free surface characterized by rough topography. The backazimuth values measured in the frequency bands centred at 1.5 and 3 Hz are almost uniformly distributed between 0 and 360°, while those measured at higher frequencies show different distributions between surface and underground. On the contrary, the earthquake envelopes show very similar coda shapes between surface and underground recordings, with an almost constant coda-amplitude ratio (between 4 and 8) in a wide frequency range.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 3
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    TOMO-ETNA experiment at Etna volcano: activities on land (2016)
    In:  Annals of Geophysics
    Details
    Publication Date: 2020-02-12
    Description: In the present paper we describe the on-land field operations integrated in the TOMO-ETNA experiment carried out in June-November 2014 at Mt. Etna volcano and surrounding areas. This terrestrial campaign consists in the deployment of 90 short-period portable three-component seismic stations, 17 Broadband seismometers and the coordination with 133 permanent seismic station belonging to Italy’s Istituto Nazionale di Geofisica e Vulcanologia (INGV). This temporary seismic network recorded active and passive seismic sources. Active seismic sources were generated by an array of air-guns mounted in the Spanish oceanographic vessel “Sarmiento de Gamboa” with a power capacity of up to 5200 cubic inches. In total more than 26,000 shots were fired and more than 450 local and regional earthquakes were recorded. We describe the whole technical procedure followed to guarantee the success of this complex seismic experiment. We started with the description of the location of the potential safety places to deploy the portable network and the products derived from this search (a large document including full characterization of the sites, owners and indication of how to arrive to them). A full technical description of the seismometers and seismic sources is presented. We show how the portable seismic network was deployed, maintained and recovered in different stages. The large international collaboration of this experiment is reflected in the participation of more than 75 researchers, technicians and students from different institutions and countries in the on-land activities. The main objectives of the experiment were achieved with great success.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 4
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    Shear wave velocity and attenuation structure of Ischia island using broad band seismic noise records (2020)
    In:  Journal of Volcanology and Geothermal Research
    Details
    Publication Date: 2021-06-11
    Description: In volcanic areas, accurate localization of earthquakes requires detailed velocity and, possibly, attenuation models, taking into account wide lithological variability and high geothermal gradients. Ischia island (Campania region, Italy) is a seismically-active volcano recently affected by a Mw 3.9 event (Casamicciola, August 21, 2017, 1 km depth). Due to the lack of a specific velocity model, the earthquakes occurred on the island were localized using the one developed for the nearby Campi Flegrei caldera. The aim of this work is the definition of a mean representative 1D shear-wave velocity (Vs) and attenuation (Q) model of the shallower crust (up to 2 km depth) of Ischia. Seismic noise array and spectral ratios techniques were applied to broad band seismic signals recorded by temporary and permanent networks updated after the August 2017 earthquake. The values of both shear-wave velocity (Vs) and quality factor (Q) are realistic, with Q values comparable with those obtained for Campi Flegrei and Stromboli volcanic areas. By taking into account stratigraphic information from deep wells and ultrasonic measurements of velocity on granite and trachytic lava samples, a geological interpretation of the resulting velocity model is provided. Such a model can have significant implications for understanding the dynamics of a volcano, mainly those leading to seismic activity.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 5
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    Seismic source analysis for recent seismicity at Mt. Vesuvius (southern Italy): preliminary results from a full waveform inversion approach (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-12-11
    Description: The detailed analysis of volcanic seismicity can allow the identification of the processes occurring in a volcanic system and obtain information about its state and evolution. In the last decades, the seismicity of Mt. Vesuvius has consisted mainly of volcano-tectonic (VT) seismic events, with an average rate of some hundreds of earthquakes per year with magnitudes between −1.0 and 2.5, located up to 6-7 km below sea level (b.s.l.). Unusual low-frequency (LF) seismicity has also been observed, localized at a depth of 5-7 km. Previous seismic source analyses applied conventional methodologies based on first pulse characteristics, which are difficult due to high background noise, low magnitude and emergent first arrivals. To overcome these challenges, we analyze here the Mt. Vesuvius seismicity over the past 20 years by using a robust probabilistic seismic source inversion tool. This methodology provides the results in terms of moment tensor solutions estimated by using seismic waveforms and waveform attributes. In agreement with previous studies, two clusters of seismicity are clearly evidenced, both in terms of depth (0-4 km and 5-7 km b.sl. for VT and LF events, respectively) and frequency content (5-15 Hz and 2-6 Hz, respectively). Our preliminary results show that: a) the probabilistic approach for the whole waveform inversion provides acceptable results even for small magnitude earthquakes, and b) both seismicity clusters show strongly heterogeneous focal mechanisms, confirming past literature studies. We attribute the latter result to a highly heterogeneous stress field beneath Mt. Vesuvius.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Urban Disaster-Prevention Strategies Using Macroseismic Fields and Fault Sources (2012)
    Details
    Publication Date: 2021-07-14
    Description: This contribution presents the general framework of the European project UPStrat-MAFA "Urban disaster Prevention Strategies using MAcroseismic Fields and FAult Sources" and its ongoing activities. A unique probabilistic procedure is being used for seismic hazard evaluation, using both macroseismic fields and characteristics of fault sources for the analysis of data from volcanic and tectonic areas: Mt. Etna, Mt. Vesuvius and Campi Flegrei (Italy), Azores Islands (Portugal), South Iceland (Iceland), Alicante-Murcia (Spain), and mainland and offshore Portugal. An improvement of urban scale vulnerability information on building and network systems (typologies, schools, strategic buildings, lifelines, and others) is proposed in the form of a global Disruption Index, with the objective to provide a systematic way of measuring earthquake impact in urbanized areas considered as complex networks. Disaster prevention strategies are considered based on an education information system, another effective component of the disaster risk reduction given by long-term activities.
    Description: Co-financed by the EU - Civil Protection Financial Instrument, in the framework the European project ”Urban disaster Prevention Strategies using MAcroseismic Fields and FAult Sources (Acronym: UPStrat-MAFA, Grant Agreement N. 23031/2011/613486/SUB/A5). http://ec.europa.eu/echo/funding/cp_projects2011_en.htm
    Description: Published
    Description: Lisbon - Portugal
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: open
    Keywords: Probabilistic hazard ; seismic risk ; urban disaster prevention strategies ; UPStrat-MAFA ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 05. General::05.03. Educational, History of Science, Public Issues::05.03.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 7
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    Attenuation and velocity structure from diffuse coda waves: Constraints from underground array data (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2021-05-12
    Description: An analysis of coda waves excited in the 0.2–20 Hz frequency band and recorded by the underground array Underseis (central Italy) has been performed to constrain both seismic attenuation at regional scale and velocity structure in the Mount Gran Sasso area. Attenuation was estimated with the MLTWA method, and shows a predominance of scattering phenomena over intrinsic absorption. The values of Qi and Qs are compatible with other estimates obtained in similar tectonic environments. Array methods allowed for a detailed study of the propagation characteristics, demonstrating that earthquake coda at frequencies greater than about 6 Hz is composed of only body waves. Coherence and spectral characteristics of seismic waves measured along the coda of local and regional earthquakes indicate that the wavefield becomes fully diffuse only in the late coda. The frequency-dependent energy partitioning between horizontal and vertical components has been also estimated and compared with synthetic values computed in a layered half-space under the diffuse field assumption. This comparison confirms that, for frequencies higher than 6 Hz, the coda appears as a sum of body waves coming from all directions while, in the low frequency range (0.2–2 Hz), the observations can be well explained by a coda wavefield composed of an equipartition mixture of surface and body waves traveling in a multiple-layered medium. A Monte-Carlo inversion has been performed to obtain a set of acceptable velocity models of the upper crust. The present results show that a broadband coda wavefield recorded in an underground environment is useful to constrain both the regional attenuation and the velocity structure of the target area, thereby complementing the results of classical array analysis of the wavefield.
    Description: Published
    Description: 34 - 42
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Energy equipartition ; Scattering ; velocity/attenuation structure ; array analysis ; Diffuse wavefield ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Seismic Signals Associated with Landslides and with a Tsunami at Stromboli Volcano, Italy (2005)
    Details
    Publication Date: 2017-04-04
    Description: In this article, we analyze the seismic signals produced by two landslides that occurred at the Stromboli volcano on 30 December 2002, recorded by both broadband and short-period seismic stations located in the 2.5–22-km distance range from the source. For both landslides, the characteristics of the low-frequency seismograms indicate a complex time history in the release of seismic energy. The first landslide occurred over the submerged part of the northwest sector of the volcano and had associated a large-amplitude, low-frequency pulse representative of the abrupt detachment of a large mass. Lower amplitude phases in the following 3 minutes possibly indicate minor detachment events. The highest amplitude, lowfrequency signals are well described by a single-force source model. The second mass-failure episode is also characterized by a complex source and can be interpreted as a multiple event, with a less abrupt onset and at least four detachments occurring during 4–5 minutes and producing low-frequency signals. Synthetic seismograms generated by a shallow single force located in the submerged area of Sciara del Fuoco and directed upslope, fit well the first low-frequency seismic pulse recorded at Stromboli and Panarea by three-component stations. From this simulation, we estimated the force exerted by the first mass failure. The estimate of the volume through two different procedures, gives values in the range of 1.0–1.5 million m3 and about 14 million m3, respectively. The landslides, which involved both the submarine and the subaerial northwest flank of the volcano, produced a tsunami that struck the coast of Stromboli Island and in a few minutes reached the other islands of the Aeolian Archipelago. Three broadband seismic stations installed on land about 100 m from the coastline at Panarea Island, located 20 km southwest of Stromboli, recorded very long period seismic signals produced by the tsunami waves. Analysis of these signals gives invaluable information on the spectral content and propagation properties of tsunami waves and on their interaction with the ground at a short distance from the coast. Synthetic tsunami waves, obtained by a landslide source model and taking into account the bathymetry of the sea surrounding Stromboli and Panarea Islands, fit the observed phenomena and the experimental data very well.
    Description: Published
    Description: 1850-1867
    Description: partially_open
    Keywords: Seismic signals ; Landslides ; Tsunami ; Stromboli Volcano ; 03. Hydrosphere::03.03. Physical::03.03.01. Air/water/earth interactions ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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    Format: 1262179 bytes
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  • 9
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    Predominant frequency variations in the ambient noise recorded in the Colfiorito basin (Umbria, Italy) (2007)
    Details
    Publication Date: 2017-04-04
    Description: The Colfiorito basin is located at the boundary between Umbria and Marche districts in Central Italy. The area was struck by several strong earthquakes in the past, and during the September 1997 to April 1998 seismic sequence, the macroseismic intensity was as large as IX (MCS scale) in the region. Ambient noise measurements are carried out over fifty points in the basin; H/V spectral ratios as well as spectral ratios using a reference rock site are calculated. Polarization analyses are also performed in narrow frequency bands where spectral amplitude peaks are observed to dominate, to discriminate preferential directions of propagation in the noise wave field which could be related to source or path effects, other than site effects. In the spectral ratios, the frequencies of the most pronounced peaks generally agree with the resonance frequencies computed for the measurement sites on the basis of 1-D velocity models, at least where no strong lateral variations of the sediment thickness are present.
    Description: Unpublished
    Description: Nice, France
    Description: open
    Keywords: microtremors ; H/V spectral ratios ; polarization ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
    Format: 900748 bytes
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  • 10
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    H/V spectral ratios and array techniques applied to ambient noise recorded in Colfiorito basin, Central Italy. (2007)
    Seismological Society of America
    Details
    Publication Date: 2017-04-04
    Description: The Colfiorito Basin is a small intramountain depression in the southern section of the Northern Apennine chain that is filled with Quaternary alluvial deposits. The presence of soft alluvial deposits has significantly influenced the level of local damage that was caused by two major earthquakes (ML 5.6 and 5.8) belonging to the swarm that started in September 1997. To verify the effects of the basin structure on the predominant frequency of seismic motion, ambient noise measurements were carried out in the Colfiorito Basin during two experiments in May and July of 2002. The horizontal-to-vertical spectral ratios (HVSRs) were calculated for data collected at four profiles in the basin. Array techniques were applied to determine the wave types that composed the noise, to estimate their apparent velocity and azimuth of propagation, and to calculate a velocity-dispersion curve from which a velocity-depth structure was derived. The data analysis shows a high amplification in the HVSR at low frequency. This feature is common to most of the sites, including the reference site, and it is interpreted as being due to weather disturbances. The peak frequencies of the spectral ratio calculated at the sites located in the center of the basin coincide with the theoretically estimated resonance frequencies. The arrayaveraged HVSR calculated for the array located in the middle of the plain has a pronounced peak at 0.9 Hz. This corresponds to the peak of the amplification function calculated on the basis of the velocity model deduced from the dispersion analysis. The HVSR method is instead unsuitable for the prediction of the resonance frequencies of sediments in the sites where strong lateral variations of basement topography are present. We measured apparent velocities in the range of 0.3–0.8 km/sec by applying f-k methods to array recordings. These values are compatible with the predominance of surface waves in the noise, as also confirmed by polarization analysis. Both Rayleigh and Love waves are present in the background seismic noise. The results obtained by applying the spatial autocorrelation method to the vertical component of the ground motion recorded at a 240-m-wide circular array deployed in the middle of the basin revealed the presence of Rayleigh waves, and f-k methods combined with polarization techniques revealed the presence of polarized Love waves. The wave-field analysis indicates two main propagation directions: the first is around N100 E in the frequency band of 1.0–2.0 Hz; this radiation can be interpreted as being generated at the east-southeast step borders of the basin. The second main direction is around N300 E in the frequency band of 2.0–3.0 Hz; its source may be a 180-m-deep depression located at the southwest corner of the basin.
    Description: Published
    Description: 490–505
    Description: reserved
    Keywords: NONE ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 556544 bytes
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