GNGTS 2019 - Atti del 38° Convegno Nazionale

186 GNGTS 2019 S essione 1.3 • We found evidence along the caldera ring-faults (e.g. offshore area of Capo Miseno) of the seismic signature of an ascent of fluids as well as the emplacement of magmatic bodies of or mud volcanoes. This finding supports previous ideas that ring-faults forms a highly permeable zone. Based on seismic stratigraphy calibration, we argue that these processes are recent (< 3.7 ka) and many are still active. Analysis of seismic datasets highlights that the submerged portion of the caldera preserves the seismic record to study and quantify caldera and post-caldera evolution phases, outlining the interplay between volcano-tectonic processes and sea-level variations. References Di Vito M. A., Isaia R., Orsi G., Southon J., de Vita S., D’Antonio M., Pappalardo L. and Piochi M.; 1999: Volcanism and deformation in the past 12 ka at the Campi Flegrei caldera (Italy). Journal of Volcanology and Geothermal Research, 91 , 221–246. Deino A.L., Orsi G., de Vita S., and Pichi, M., 2004. The age of the Neapolitan Yellow Tuff caldera-forming eruption (Campi Flegrei caldera, Italy) assessed by 40Ar/39Ar dating method. Journal of Volcanology and Geothermal Research, 133 , 157–170. Marturano A., Isaia R., Aiello G. and Barra, D.; 2018: Complex dome growth at Campi Flegrei caldera (Italy) in the last 15 ka. Journal of Geophysical Research: Solid Earth, 123 . https://doi.org/10.1029/ 2018JB015672. Sacchi M., Pepe F., Corradino M., Insinga D.D., Molisso F. and Lubritto C.; 2014: The Neapolitan Yellow Tuff caldera offshore the Campi Flegrei: stratal architecture and kinematic reconstruction during the last 15 ky. Mar. Geol., 354 , 15–33. Steinmann L., Spiess V. and Sacchi M.; 2016: The Campi Flegrei caldera (Italy): formation and evolution in interplay with sea-level variations since the Campanian Ignimbrite eruption at 39 ka. J. Volcanol. Geotherm. Res., 327 , 361–374. Steinmann L., Spiess V. and Sacchi M.; 2018: The Post-collapse evolution of a coastal caldera system: Insights from a 3D multichannel seismic survey from the Campi Flegrei caldera (Italy). J. Volcanol. Geotherm. Res., 349 , 83–98. FULL WAVEFORM INVERSION OF TRANSMITTED WAVES FOR THE ESTIMATION OF THE VELOCITY STRUCTURE ALONG THE CROP/18A SEISMIC PROFILE - LARDERELLO GEOTHERMAL AREA A. Mazzotti, A. Tognarelli, E. Stucchi Earth Sciences Department, University of Pisa, Italy Introduction. Volcanic and geothermal areas often pose many challenges to the imaging of the subsurface by reflection seismology. The peculiar nature and structure of the volcanic rocks that often determine small acoustic impedance contrasts, the troublesome near surface conditions, frequently characterized by strongly varying elevations and lateral transitions, conjure to make the acquisition and the processing of reflection data extremely difficult. One of such cases is the geothermal area of Larderello (southern Tuscany, Italy), where reflection imaging has anyhow shown several successes, especially in highlighting the presence and shape of deep reflectors (the well known “K-horizon”), and where the seismic profile CROP/18A is located. What we propose here is to make use of the transmitted waves (mainly diving and refracted P-waves), which are discarded in reflection seismology approaches, to estimate the high-resolution P-wave velocity field that may be used as a direct interpretation asset, complementing reflection imaging. In fact, looking at one example of the recorded seismograms, a common-shot gather of the CROP/18A transect (Fig. 1), it is evident that while reflections are hardly visible, the portion of the seismograms dominated by the transmitted waves stands out from the noise that contaminates the whole data. Therefore, considering the