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  • Articles  (7)
  • 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring  (6)
  • Chemical Engineering
  • Chemistry
  • Organic Chemistry
  • AGU  (7)
  • 2005-2009  (7)
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  • Articles  (7)
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  • 2005-2009  (7)
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  • 1
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    Evidence for ground motion polarization on fault zones of mt. etna volcano (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: During local and regional earthquakes, an evident amplification of horizontal ground motion is observed at two seismological stations near the Tremestieri fault, on the southeastern flank of Mt. Etna volcano. Rotated-component spectral ratios show a narrow spectral peak around 4-Hz along a N40°E direction. A conventional polarization analysis using the eigenvectors of the covariance matrix confirms the very stable directional effect enhancing the approximately NE-SW elongation of the horizontal ground motion in the fault zone. The effect is evident during the entire seismogram and independent of source backazimuth as well as distance and depth of earthquakes. The same polarization is observed in ambient noise as well. This consistency allowed us to use microtremors for checking ground motion polarization along and across the Tremestieri fault zone with a high spatial resolution. The result is a stable polarization of horizontal motion in the entire area, interesting a broad frequency band. To check whether this ground motion property is recurrent and understand a possible relationship with fault strike, faulting style, or orientation of fractures, ambient noise was recorded on other mapped faults of the Mt. Etna area, the Moscarello, Acicatena and Pernicana faults. The latter, in particular, is characterized by different strike and faulting style. A systematic tendency of ambient noise to be polarized is found in all of the faults. A picture emerges where normal faults of the eastern flank show a E-W to NE-SW polarization that changes on the Pernicana fault, which develops approximately E-W and is characterized by a prevailing NW-SE to NS polarization. Directions of polarization were never parallel to the fault strike. Moreover, polarization persists too far away from the fault trace, excluding an effect limited to a narrow low velocity zone hosted between harder wall rocks. Both these observations rule out an interpretation in terms of fault-trapped waves. The cause of observed polarizations will be the subject of future studies. However, the consistency with recent results of velocity anisotropy in a part of the investigated area suggests a possible role of attenuation anisotropy on horizontal amplitude variations versus azimuth.
    Description: Published
    Description: B10306
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: polarization ; fault zones ; Etna volcano ; microtremors ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 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::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Spatial mapping of the b value at Mount Etna, Italy, using earthquake data recorded from 1999 to 2005 (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The spatial pattern of the b value of the frequency-magnitude relation has been analyzed using gridding techniques beneath Mount Etna, Italy. A regional data set of 2900 events with Md (duration magnitude) 1.5 up to 15 km depth occurring between August 1999 and December 2005 has been used. Two regions with an abnormally high b value have been found, one centered beneath the southern part of the Valle del Bove, above the 6 km below sea level (bsl) deep basement, and the other beneath the summit region 2 km bsl east of the Central Craters. We can infer that these high b value anomalies are regions of increased crack density, and/or high pore pressure, related to the presence of nearby magma storage. This interpretation is supported by all the available geophysical evidence, such as tomographic studies and geodetic deformation measurements. The data set has also been subdivided into five periods, corresponding to different phases of volcanic activity: 2001 preeruption, 2001 eruptive, 2002–2003 preeruption, 2002–2003 eruptive, and 2002–2003 posteruption. The minimum magnitude of completeness, Mc, and the b value were computed for each period. A volume of anomalously high b values can be observed in each of these periods (except for the 2002–2003 preeruption interval). This approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated.
    Description: Published
    Description: B12303
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: b value ; Mount Etna ; frequency-magnitude relation ; magmatic intrusions ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    First observations of non-volcanic, long-period seismicity in the Central Apennines, Italy (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We report unprecedented observations of long-period (LP) seismicity in non-volcanic setting. Our data are from the Central-Northern sector of the Apennine chain, Italy. For this area, intense CO2 circulation of mantle origin has been documented by either groundwater composition and borehole measurements. We perform waveform correlation and stacking to obtain reliable epicenter estimates. Following Chouet's crack model, we find that both the quality factor and dominant frequency of LP oscillations are consistent with the sustained resonance of a wet crack filled by a water-CO2 mixture.
    Description: Published
    Description: L12303
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: Long-period events ; apennines ; fluids ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Coda wave interferometric detection of seismic velocity changes associated with the 1999 M = 3.6 event at Mt. Vesuvius (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We detect seismic wave velocity changes at Mt. Vesuvius, using doublets and the Coda Wave Interferometry method. The high sensitivity of multiply scattered coda waves to temporal changes in the medium allows us to detect velocity variation smaller than 0.4%. We use 17 doublets, some of them grouped in families of multiplets, spanning January 1996 to December 1999. Data show a systematic increase in velocity from 1996 to end- September 1999, followed by a rapid drop in velocity. This drop immediately precedes a sustained swarm of VT-type earthquakes, including the 9th October 1999 M = 3.6 event, the largest in the region since at least 1972. We propose a long term fluid pressurization followed by influx as a possible causative mechanism.
    Description: Published
    Description: L06306
    Description: reserved
    Keywords: NONE ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 1508425 bytes
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  • 5
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    Ocean bottom seismometers deployed in the Tyrrhenian Sea (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The Institute for Geophysics at Hamburg University and the Research Center for Marine Geoscience (GEOMAR) of Kiel University have developed new, wideband ocean bottom seismic stations for long-term, deep sea deplyments of up to 1 year.
    Description: Published
    Description: 309-315
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: open
    Keywords: Ocean Bottom Seismometer ; Tyrrhenian Sea ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Reactive halogen chemistry in volcanic plumes (2007)
    AGU
    Details
    Publication Date: 2023-01-19
    Description: Bromine monoxide (BrO) and sulphur dioxide (SO2) abundances as a function of the distance from the source were measured by ground-based scattered-light Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) in the volcanic plumes of Mt. Etna on Sicily, Italy in August-October 2004 and May 2005 and Villarica in Chile in November 2004. BrO and SO2 spatial distributions in a cross section of Mt. Etna’s plume were also determined by Imaging DOAS. We observed an increase in the BrO/SO2 ratio in the plume from below the detection limit near the vent to about 4.5 x 10-4 at 19 km (Mt. Etna) and to about 1.3 x 10-4 at 3 km (Villarica) distance, respectively. Additional attempts were undertaken to evaluate the compositions of individual vents on Mt. Etna. Furthermore, we detected the halogen species ClO and OClO. This is the first time that OClO could be detected in a volcanic plume. Using calculated thermodynamic equilibrium compositions as input data for a one–dimensional photochemical model, we could reproduce the observed BrO and SO2 vertical columns in the plume and their ratio as function of distance from the volcano as well as vertical BrO and SO2 profiles across the plume with current knowledge of multiphase halogen chemistry, but only when we assumed the existence of an ”effective source region”, where volcanic volatiles and ambient air are mixed at about 600°C (in the proportions of 60% and 40%, respectively)
    Description: Published
    Description: D06311
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Description: open
    Keywords: Chemistry ; Volcanic Plumes ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Source and Qp parameters from pulse width inversion of microearthquake data in southeastern Sicily, Italy (2005)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Source and Qp parameters were estimated from the inversion of first arrival P waveform durations of about 300 microearthquakes recorded at a digital seismic network operating in southeastern Sicily. The average risetime and pulse width at each station do not show large differences, allowing us to exclude significant differential attenuation site effects. A first Qp estimate was obtained by applying the classical risetime method, under the assumption of a point-like source time function. In order to investigate the effect of directivity due to the finiteness of seismic sources, new nonlinear relationships, based on a circular crack model rupturing at a constant velocity, were numerically built. These relationships were used to formulate a nonlinear inverse method for retrieving source (radius, dip, and strike of the circular crack) and Qp parameters from the inversion of risetime and pulse width data. The application of the method produced a better fit of the observed data and a Qp value higher than that obtained by applying the risetime method. The discrepancy between the different Q estimates may be due to a trade-off among source dimension and Qp, as we inferred from a test on a subset of low-magnitude events (Ml ≤ 2.5). A good agreement with independent estimates of fault plane solutions, as inferred from P polarities and S polarizations, was found. The estimated stress drops are generally very low (0.1–10 bars). This suggests that the background seismic activity in southeastern Sicily is related to fault segments and/or weakened zones where great stress accumulations are hindered.
    Description: Published
    Description: 1-14
    Description: partially_open
    Keywords: source and Qp parameters ; risetime ; pulse width ; attenuation ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 490 bytes
    Format: 654914 bytes
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