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Scarpa, Roberto
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- PublicationRestrictedJoint observation of coherent coda waves at surface and underground arrays(2013-04-16)
; ; ; ; ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Galluzzo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; Università di Salerno; ; ; 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.243 25 - PublicationRestrictedContinuous tracking of volcanic tremor at Mount Etna, Italy(2007-05)
; ; ; ; ; ;Di Lieto, B.; Dipartimento di Fisica, Università degli Studi di Salerno, Salerno, Italy ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Zuccarello, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;La Rocca, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; Dipartimento di Fisica, Università degli Studi di Salerno, Salerno, Italy; ; ; ; Using data from two dense array of short period seismometers, we analyse the kinematic properties of volcanic tremor preceding and accompanying the 2004–2005 eruption of Etna Volcano, Italy. Results from slowness analyses indicate the action of at least two distinct sources. The first dominates the pre-eruptive period, and is likely associated with the main plumbing system feeding the Summit and southeast craters. Following the onset of the eruption, secondary directions of wave-arrival encompass the eruptive fissures, located on the lower eastern flank of the southeast crater. Nonetheless, significant energy radiation from this latter source was also occurring prior to the onset of the lava effusion, likely suggesting the presence of a resident magma batch, in agreement with independent petrologic and geochemical data.372 30 - PublicationOpen AccessTeleseismic P-residual study in the Italian region - inferences on large scale anisotropic structure of the subcrustal lithosphere(1998-04)
; ; ; ;Plomerová, J.; Geophysical Institute, Czech Academy of Sciences, Prague, Czech Republic ;Babuska, V.; UNESCO, Division of Earth Sciences, Paris, France ;Scarpa, R.; Dipartimento di Fisica, Università dell'Aquila, Coppito, L'Aquila, Italy; ; Jeffreys-Bullen (absolute) and relative P-wave travel-time residuals were analyzed over Italy and its surrounding using P arrival times from the ISC bulletins supplemented by the data from local observatories. We analyzed the travel-time station corrections by two independent methods to obtain information on lateral variations of the velocity structure over the area and a view of possible upper mantle anisotropy. In the first method, the station corrections are computed as a constant and two cosine terms with appropriate phase shifts. Besides a static term, the second method allows us to study the relative residuals in dependence both on azimuths and incidence angles and thus to investigate their spatial variations and to map lateral variations of anisotropic structure of the subcrustal lithosphere. The high and low-velocity directions inferred from the spatial distribution of the relative residuals as well as the high- and low-velocity upper mantle heterogeneities reflect the geodynamic development of the region, governed by the collision between the African and Eurasian plates152 434 - PublicationRestrictedShallow velocity structure of Stromboli volcano, Italy, derived from small-aperture array measurements of Strombolian tremor(1998-06)
; ; ; ; ; ; ;Chouet, B.; U.S. Geological Survey ;De Luca, G.; Dipartimento di fisica, Università degli studi dell'Aquila ;Milana, G.; Servizio Sismico Nanionale ;Dawson, P.; U.S. Geological Survey ;Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; Dipartimento di fisica, Università degli studi dell'Aquila; ; ; ; ; The properties of the tremor wave field at Stromboli are analyzed using data from small-aperture arrays of short-period seismometers deployed on the north flank of the volcano. The seismometers are configured in two semi-circular arrays with radii of 60 and 150 m and a linear array with length of 600 m. The data are analyzed using a spatiotemporal correlation technique specifically designed for the study of the stationary stochastic wave field of Rayleigh and Love waves generated by volcanic activity and by scattering sources distributed within the island. The correlation coefficients derived as a function of frequency for the three components of motion clearly define the dispersion characteristics for both Rayleigh and Love waves. Love and Rayleigh waves contribute 70% and 30%, respectively, of the surface-wave power. The phase velocities of Rayleigh waves range from 1000 m/sec at 2 Hz to 350 m/sec at 9 Hz, and those for Love waves range from 800 to 400 m/sec over the same frequency band. These velocities are similar to those measured near Puu Oo on the east rift of Kilauea Volcano, Hawaii, although the dispersion characteristics of Rayleigh waves at Stromboli show a stronger dependence on frequency. Such low velocities are consistent with values expected for densely cracked solidified basalt. The dispersion curves are inverted for a velocity model beneath the arrays, assuming those dispersions represent the fundamental modes of Rayleigh and Love waves.268 28 - PublicationOpen AccessTopography effects in the polarization of coda waves: a comparison between surface and deep recordings(2012)
; ; ; ; ; ; ; ; ; ; ; Local and regional earthquakes recorded in 2007 by two seismic arrays at Gran Sasso (Italy), one located at surface and one at 1.4 km depth, have been analyzed. Polarization properties of the seismic wavefield have been estimated at both arrays on a short sliding window and in several frequency bands. Array methods were also applied, and the estimated slowness and backazimuth were used to compute the stacking of phase shifted signals in order to improve the signal to noise ratio. Results of polarization computed over single station and array stacked signals have been compared between the two arrays. A well defined polarization azimuth, roughly perpendicular to the main massif ridges, is evident at surface in a broad frequency band. This is observed for earthquake body waves and coda waves. On the contrary, underground the same effect is slightly visible only at very low frequency.75 34 - PublicationOpen AccessLONG-TERM TEMPERATURE MONITORING OF VOLCANIC AREAS BY DISTRIBUTED OPTICAL FIBER SENSORS(2008-09)
; ; ; ; ; ; ; ;Bernini, R.; IREA- CNR, Napoli, Italy ;Gravina, R.; IREA- CNR, Napoli, Italy ;Minardo, A.; Dipartimento di Ingegneria dell’Informazione, Seconda Università di Napoli, Aversa (CE), Italy ;Zeni, L.; Dipartimento di Ingegneria dell’Informazione, Seconda Università di Napoli, Aversa (CE), Italy ;Petrillo, Z.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; Dipartimento di Fisica, Università degli studi di Salerno, Italy; ; ; ; ; ; We present the first results of long- term monitoring of temperature profiles at the Campi Flegrei caldera. The measurements were carried out along a 76 meters-deep borehole already equipped with a borehole strain-meter. We installed a cable containing a loop of optical fiber in order to use a fiber-optics distributed sensor based on stimulated Brillouin scattering. The obtained data are consistent with results of both deep and surface geothermal explorations and indicate that geothermal gradient can be efficiently measured and monitored by the proposed technique.157 297 - PublicationOpen AccessUnderground earth strain and seismic radiation measurements with a laser interferometer and a dense small-aperture seismic array(1997-10)
; ; ; ; ; ; ;Amoruso, A.; Dipartimento di Fisica, Università dell'Aquila, Italy ;Crescentini, L.; Dipartimento di Fisica, Università dell'Aquila, Italy ;De Luca, G.; Laboratori Nazionali del Gran Sasso, Istituto Nazionale di Fisica Nucleare, Assergi, L'Aquila, Italy ;Scarpa, R.; Dipartimento di Fisica, Università dell'Aquila, Italy ;Abril, M.; Instituto Andaluz de Geofisica y Prevencion de Desastres Sismicos, Granada, Spain ;Cirella, Al.; Dipartimento di Fisica, Università dell'Aquila, Italy; ; ; ; ; This paper describes two geophysical instruments, installed in the underground physics laboratories of Gran Sasso (LNGS-INFN), located in the seismic zone of the Central Apennines, Italy. These instruments monitor strain and seismic radiation with very high sensitivity: one is a 90 m-long laser interferometer, sensitivity 3 x 10-12, frequency response 10-7-10-2 Hz, and has been operating since 1994. The other is a small-aperture seismic array composed of 21 three-component short period (Mark L4C-3D) and 3 broadband (Guralp CMG-3ESP) seismometers. This dense array will be in operation at the beginning of 1998.243 328 - PublicationOpen AccessERUPTIVE HISTORY, SEISMIC ACTIVITY AND GROUND DEFORMATIONS AT MT VESUVIUS, ITALY(1985)
; ; ; ; ; ;Bonasia, V.; University of Naples ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Pingue, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scandone, R.; University of Rome III ;Scarpa, R.; University of Salerno; ; ; ; We describe the eruptive history and seismicity and ground deformation of Mt. Vesuvius in the time interval 1970-1982368 677 - PublicationOpen AccessDynamic strain anomalies detection at Stromboli before 2019 vulcanian explosions using machine learning(2022-08-16)
; ; ; ; ; ; ; ; ; ; ; Identifying and characterizing the dynamics of explosive activity is impelling to build tools for hazard assessment at open-conduit volcanoes: machine learning techniques are now a feasible choice. During the summer of 2019, Stromboli experienced two paroxysmal eruptions that occurred in two different volcanic phases, which gave us the possibility to conceive and test an early-warning algorithm on a real use case: the paroxysm on July, 3 was clearly preceded by smaller and less perceptible changes in the volcano dynamics, while the second paroxysm, on August 28 concluded the eruptive phase. Among the changes observed in the weeks preceding the July paroxysm one of the most significant is represented by the shape variation of the ordinary minor explosions, filtered in the very long period (VLP 2–50 s) band, recorded by the Sacks-Evertson strainmeter installed near the village of Stromboli. Starting from these observations, the usage of two independent methods (an unsupervised machine learning strategy and a cross-correlation algorithm) to classify strain transients falling in the ultra long period (ULP 50–200 s) frequency band, allowed us to validate the robustness of the approach. This classification leads us to establish a link between VLP and ULP shape variation forms and volcanic activity, especially related to the unforeseen 3 July 2019 paroxysm. Previous warning times used to precede paroxysms at Stromboli are of a few minutes only. For paroxysmal events occurring outside any long-lasting eruption, the initial success of our approach, although applied only to the few available examples, could permit us to anticipate this time to several days by detecting medium-term strain anomalies: this could be crucial for risk mitigation by prohibiting access to the summit. Our innovative analysis of dynamic strain may be used to provide an early-warning system also on other open conduit active volcanoes.117 13 - PublicationRestrictedTHE 23 NOVEMBER 1980 SOUTHERN ITALY EARTHQUAKE(1983-02)
; ; ; ; ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Iannaccone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Scarpa, R.; University of Salerno; ; ; The seismic activity associated with the catastrophic southern Italy earth- quake was monitored by 11 seismic stations operating before this event, within an epicentral distance of 200 km, and by 32 additional short-period seismom- eters installed soon after the main shock. The hypocenter of this event was located at 40°46'N and 15°18'E, at 16 km depth. The fault-plane solution reveals normal faulting, with tensile axis dipping 18 ° and oriented orthogonal to the axis of the Apennines chain. This mechanism is in good agreement with the stress pattern inferred from some previous earthquakes and the local seismotectonics. The hypocenter locations of more than 600 aftershocks, with local magnitudes greater than 2.4, show a pronounced alignment extending for about 70 km, oriented north 120 ° and scattered laterally less than 15 km. These events are mostly concentrated between 8 and 16 km depth. A cluster of aftershocks occurred close to the hypocenter of the main shock covering a region elongated 25 km which corresponds also to the highly damaged area. No significant spreading of the aftershock area with time is observed, but one of the events with higher magnitude (M, = 4.8, 14 February 1981) is displaced 20 km NW from the tip of the aftershock region. The time evolution of the number of aftershocks fits well Omorrs hyperbolic law with a decay coeffcient of 1.07 __. 0.06. The possibility of a future delayed multiple sequence of large events, as already observed in the past along the central and southern Apennines, is discussed. In particular, a relatively high seismic potential seems to exist along the northern boundary of the 1980 rupture segment.321 42
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