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Dello Iacono, Dario
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Dello Iacono, Dario
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- PublicationOpen AccessConverted phase identification and retrieval of Vp/Vs ratios from move-out reflection analysis: application to the Campi Flegrei caldera(2007)
; ; ; ; ; ;Vassallo, M.; Dipartimento di Scienze Fisiche, Università di Napoli Federico II (RISSC-Lab), Italy ;Zollo, A.; Dipartimento di Scienze Fisiche, Università di Napoli Federico II (RISSC-Lab), Italy ;Dello Iacono, D.; Dipartimento di Scienze Fisiche, Università di Napoli Federico II (RISSC-Lab), Italy ;Maercklin, N.; Dipartimento di Scienze Fisiche, Università di Napoli Federico II (RISSC-Lab), Italy ;Virieux, J.; Institute Geosciences Azur, CNRS, Nice, France; ; ; ; Here, we propose a method for the determination of Vp/Vs ratios in a horizontally layered propagation media using maximization of a coherency function along theoretical travel-times of PS reflected phases. The theoretical travel-times are computed using the information about the propagation media that is extracted by velocity analysis or by topographic analysis performed on the first arrivals. The method is also a valid tool for the identification of the PS phases associated with a fixed seismic reflector, and it is particularly suitable for data that is stored in common mid-point and common conversion point bin- ning; for this kind of data the hypothesis of horizontally and layered media can usually be verified. We applied the method to both simulated and real datasets. The use of the real data that was acquired in the Campi Flegrei caldera (southern Italy) allowed us to estimate a relatively high Vp/Vs ratio (3.5 ± 0.6) for a very shallow layer (maximum depth, 600 m). This hypothesis has been tested by theoretical rock physical modeling of the Vp/Vs ratios as a function of porosity, suggesting that the shallow layer appears to be formed of unconsolidated, water-saturated, volcanic and marine sediments that filled Pozzuoli Bay during the post-caldera activity.228 209 - PublicationOpen AccessMerging Active and Passive Data Sets in Travel-Time Tomography: The Case Study of Campi Flegrei Caldera (Southern Italy)(2008-10)
; ; ; ; ;Battaglia, J.; Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II ;Zollo, A.; Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II ;Virieux, J.; UMR Géosciences Azur ;Dello Iacono, D.; Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II; ; ; We propose a strategy for merging both active and passive data sets in linearized tomographic inversion. We illustrate this in the reconstruction of 3D images of a complex volcanic structure, the Campi Flegrei caldera, located in the vicinity of the city of Naples, southern Italy. The caldera is occasionally the site of significant unrests characterized by large ground uplifts and seismicity. The P and S velocity models of the caldera structure are obtained by a tomographic inversion based on travel times recorded during two distinct experiments. The first data set is composed of 606 earthquakes recorded in 1984 and the second set is composed of recordings for 1528 shots produced during the SERAPIS experiment in 2001. The tomographic inversion is performed using an improved method based on an accurate finite-difference traveltime computation and a simultaneous inversion of both velocity models and earthquake locations. In order to determine the adequate inversion parameters and relative data weighting factors, we perform massive synthetic simulations allowing one to merge the two types of data optimally. The proper merging provides high resolution velocity models, which allow one to reliably retrieve velocity anomalies over a large part of the tomography area. The obtained images confirm the presence of a high P velocity ring in the southern part of the bay of Pozzuoli and extends its trace inland as compared to previous results. This annular anomaly represents the buried trace of the rim of the Campi Flegrei caldera. Its shape at 1.5 km depth is in good agreement with the location of hydrothermalized lava inferred by gravimetric data modelling. The Vp/Vs model confirms the presence of two characteristic features. At about 1 km depth a very high Vp/Vs anomaly is observed below the town of Pozzuoli and is interpreted as due to the presence of rocks that contain fluids in the liquid phase. A low Vp/Vs body extending at about 3–4 km depth below a large part of the caldera is interpreted as the top of formations that are enriched in gas under supercritical conditions.175 349 - PublicationOpen AccessCombining active and passive data for velocity reconstruction(2007)
; ; ; ; ;Battaglia, J.; Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, Clermont-Ferrand, France ;Dello Iacono, D.; Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, Napoli, Italy ;Zollo, A.; Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, Napoli, Italy ;Virieux, J.; UMR Geosciences Azur, Sophia Antipolis, France; ; ; 120 132 - PublicationRestrictedSeismic images and rock properties of the very shallow structure of Campi Flegrei caldera (southern Italy)(2009-03)
; ; ; ; ; ;Dello Iacono, Dario; Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Napoli, Italy ;Zollo, Aldo; Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Napoli, Italy ;Vassallo, Maurizio; Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Napoli, Italy ;Vanorio, Tiziana; Stanford Rock Physics Laboratory, Stanford University, Stanford, CA, USA ;Judenherc, Sebastien; Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Napoli, Italy - Agecodagis, sarl, Rieux Volvestre, France; ; ; ; In September 2001, an extensive active-seismic investigation (Serapis experiment) was carried out in the Gulfs of Naples and Pozzuoli, with the aim of investigating and reconstructing the shallow crustal structure of the Campi Flegrei caldera, and possibly identifying its feeding system at depth. The present study provides a joint analysis of the very shallow seismic reflection data and tomographic images based on the Serapis dataset. This is achieved by reflection seismic sections obtained by the 3D data gathering and through refined P-velocity images of the shallowest layer of Pozzuoli Gulf (z<1,000 m). From the refined Vp model, the overall picture of the velocity distribution confirms the presence of a complex arc-shaped anomaly that borders the bay offshore. The deeper part of the anomaly (beneath 700 m, with Vp>3,500 m/s) correlates with units made up of agglomerate tuffs and interbedded lava, which form the southern edge of the caldera, which was probably formed following the two large ignimbritic eruptions that marked the evolutionary history of the area under study. The upper part of the anomaly that tends to split into two parallel arcs is correlated with dikes, volcanic mounds and hydrothermal alteration zones noted in previous shallow reflection seismic analyses. The depth of the transition between the upper and lower parts of the anomaly is characterized by an abrupt Vp increase on the one-dimensional (1D) profiles extracted from the 3D tomographic model and by the presence of a strong reflector located at about 0.6/0.7 s Two Way Time (TWT) on Common Mid Point gathers. The move-out velocity analysis and stack of the P–P and P–S reflections at the layer bottom allowed to estimate relatively high Vp/Vs values (3.7±0.9). This hypothesis has been tested by a theoretical rock physical modeling of the Vp/Vs ratio as a function of porosity suggesting that the shallow layer is likely formed by incoherent, water saturated, volcanic and marine sediments that filled Pozzuoli Bay during the post-caldera activity.143 27