GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.3 249 (3) the procedure used in this work represents a new multi-parametric approach that can be used in a volcanic environment; it shows how the interpretation of velocity tomographic images can be complemented with the ones obtained by stratigraphic analysis and resistivity profiles, and, most of all, how this joint interpretation leads to a more robust and reliable interpretation of complex hydrothermal system; (4) the complex interactions (deep fluids, hydrothermal system, geological structures) between deep and shallowsources and structures allowus to use the shallowhydrothermal system processes as a constrain for the fluid migration processes occurring at depth. References Chiodini, G. et al. CO2 degassing and energy release at Solfatara volcano, Campi Flegrei, Italy. Journal Geophysical Research. 106, 16213–16221(2001). Serra, M. et al. A strongly heterogeneous hydrothermal area imaged by surface waves: the case of Solfatara, Campi Flegrei, Italy. Geophysical Journal International. 205, 1813-1822(2016). Gresse, M. et al. Three-Dimensional Electrical Resistivity Tomography of the Solfatara Crater(Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System. Journal of Geophysics Research: Solid Earth , 122(11), 8749-8768(2017). De Landro, G. et al. 3D ultra-high resolution seismic imaging of shallow Solfatara crater in Campi Flegrei(Italy): New insights on deep hydrothermal fluid circulation processes. Scientific Reports 7.1(2017): 3412. Gammaldi, S. et al. High resolution, multi-2D seismic imaging of Solfatara crater(Campi Flegrei Caldera, southern Italy) from active seismic data. Accepted for publication on Journal of Volcanology and Geothermal Research (2018). PRELIMINARY ESTIMATION OF THE SHEAR WAVE VELOCITY MODEL OF ISCHIA ISLAND USING AMBIENT NOISE BROAD BAND RECORDS D. Galluzzo 1 , L. Nardone 1 , R. Manzo 3 , R. Di Maio 3 , M. Moretti 2 , F. Bianco 1 , M. Orazi 1 1 Istituto Nazionale di Geofisica e Vulcanologia, Sez. di Napoli, Osservatorio Vesuviano, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Sez. di Roma Osservatorio Nazionale Terremoti, Italy 3 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università di Napoli Federico II, Italy Introduction. On August 21, 2017, at 18:57 UTC, an earthquake of M D 4.0 occurred in Casamicciola, district of Ischia island at about 2 Km km depth. In volcanic areas, such as the Ischia Island, the precise localization of the earthquakes requires specific velocity models, both for the wide lithological variability and for the high geothermal gradient. These models are available, for example, for the Vesuvius and for the Campi Flegrei areas, but not for the Island of Ischia because they need to use the local seismicity. Since 1999, at least 78 earthquakes have been recorded on Ischia (updated to 21 February 2018) (D’Auria et al. , 2018) and have been localized using the model used for the Campi Flegrei, on the basis of the similar geological and volcanological context of the two volcanoes. Therefore, the aim of this work is the definition of average 1-D shear-wave velocity model of the shallower crust of Ischia using ambient noise array techniques and spectral ratios evaluated on broad band seismic signals recorded by mobile and permanent networks deployed in the last year. Dataset and analysis. After the M D 4.0 earthquake, that hit Casamicciola on August 21, the permanent network (CAI, IFOR, IMTC and IOCA) was implemented with other five seismic stations and six seismic stations of the mobile network (T136* in Fig. 1). All permanent network stations, equipped with broad band, accelerometer and short period sensors, transmit the seismic signals in real-time for seismic surveillance purposes. The stations