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Cros, E.
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Cros, E.
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- PublicationRestrictedHigh-resolution shallow seismic tomography of a hydrothermal area: application to the Solfatara, Pozzuoli(2012)
; ; ; ; ; ; ; ; ;Letort, J.; ISTERRE, Institut des Sciences de la Terre, CNRS UMR 5275, Universit´e Grenoble 1, France. ;Roux, P.; ISTERRE, Institut des Sciences de la Terre, CNRS UMR 5275, Universit´e Grenoble 1, France. ;Vandemeulebrouck, J.; ISTERRE, Institut des Sciences de la Terre, CNRS UMR 5275, Université de Savoie, Chamb´ery, France ;Coutant, O.; ISTERRE, Institut des Sciences de la Terre, CNRS UMR 5275, Universit´e Grenoble 1, France. ;Cros, E.; ISTERRE, Institut des Sciences de la Terre, CNRS UMR 5275, Universit´e de Savoie, Chamb´ery, France ;Wathelet, M.; Dipartimento di Scienze della Terra, Universit`a di Perugia, Perugia, Italy ;Cardellini, C.; Dipartimento di Scienze della Terra, Universit`a di Perugia, Perugia, Italy ;Avino, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; ; ; The Solfatara is one of the major volcanoes of the Phlegrean Fields (Campi Flegrei) volcanic complex, and it is located in a densely populated area a few kilometres west of the city of Naples. It is an active resurgent caldera that has been characterized by a rich history of surface–ground deformation and soil diffuse degassing and fumarolic emissions, which are indications of the top of a hydrothermal plume. A seismic survey was completed in May 2009 for the characterization of the main subsurface features of the Solfatara. Using the complete data set, we have carried out surface wave inversion with high spatial resolution. A classical minimization of a least-squares objective function was first computed to retrieve the dispersion curves of the surface waves. Then, the fitting procedure between the data and a three-sedimentlayer forward model was carried out (to a depth of 7 m), using an improved version of the neighbourhood algorithm. The inversion results indicate a NE-SW fault, which is not visible at the surface. This was confirmed by a temperature survey conducted in 2010. A passive seismic experiment localized the ambient noise sources that correlate well with the areas of high CO2 flux and high soil temperatures. Finally, considering that the intrinsic attenuation is proportional to the frequency, a centroid analysis provides an overview of the attenuation of the seismic waves, which is closely linked to the petrophysical properties of the rock. These different approaches that merge complete active and passive seismic data with soil temperature and CO2 flux maps confirm the presence of the hydrothermal system plume. Some properties of the top of the plume are indicated and localized.326 29 - PublicationOpen AccessGas and seismicity within the Istanbul seismic gap(2018-05)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.697 79