http://hdl.handle.net/2122/199 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/2872 Titolo: The permanent thermal infrared network for the monitoring of hydrothermal activity at the Solfatara and Vesuvius volcanoes.<br/><br/>Autori: Vilardo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Augusti, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Granieri, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Caliro, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Minopoli, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Terranova, C.<br/><br/>Abstract: In this paper we describe the activities carried out for the realization of an image surveillancesystems, in the thermal infrared (TIR) wavelengths range, for the continuous long-termmonitoring of the shallow thermal structure of the Solfatara (Campi Flegrei) and Vesuviusvolcanoes. The system implementation was pursued by both acquiring and integrating all thetechnological instruments necessary to operate an instrumental system constituted by: anetwork of remote monitoring stations; a transmission system for the image datacentralization; a control unit for both the remote stations control and the acquired dataprocessing. The analysis of two-years long series of IR images collected at the Solfataraallowed us to evaluate, in the observation period, the main thermal features of the majorfumarole field located in the SE inner slope of the Solfatara crater. http://hdl.handle.net/2122/2580 Titolo: A thermal pressurization model for the spontaneous ...: 2. Traction evolution and dynamic parameters<br/><br/>Autori: Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: We investigate the dynamic traction evolution during the spontaneous propagation ofa 3-D earthquake rupture governed by slip-weakening or rate- and state-dependentconstitutive laws and accounting for thermal pressurization effects. The analyticalsolutions as well as temperature and pore pressure evolutions are discussed in thecompanion paper by Bizzarri and Cocco. Our numerical experiments reveal that frictionalheating and thermal pressurization modify traction evolution. The breakdown stress drop,the characteristic slip-weakening distance, and the fracture energy depend on the slippingzone thickness (2w) and hydraulic diffusivity (w). Thermally activated pore pressurechanges caused by frictional heating yield temporal variations of the effective normalstress acting on the fault plane. In the framework of rate- and state-dependent friction,these thermal perturbations modify both the effective normal stress and the frictioncoefficient. Breakdown stress drop, slip-weakening distance, and specific fracture energy(J/m2) increase for decreasing values of hydraulic diffusivity and slipping zone thickness.We propose scaling relations to evaluate the effect of w and w on these physicalparameters. We have also investigated the effects of choosing different evolution laws forthe state variable. We have performed simulations accounting for the porosity evolutionduring the breakdown time. Our results point out that thermal pressurization modifiesthe shape of the slip-weakening curves. For particular configurations, the traction versusslip curves display a gradual and continuous weakening for increasing slip: in these cases,the definitions of a minimum residual stress and the slip-weakening distance becomemeaningless. http://hdl.handle.net/2122/2579 Titolo: A thermal pressurization model for the spontaneous dynamic rupture propagation on a three-dimensional fault: 1. Methodological approach<br/><br/>Autori: Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: We investigate the role of frictional heating and thermal pressurization on earthquakeruptures by modeling the spontaneous propagation of a three-dimensional (3-D) crack on aplanar fault governed by assigned constitutive laws and allowing the evolution ofeffective normal stress. We use both slip-weakening and rate- and state-dependentconstitutive laws; in this latter case we employ the Linker and Dieterich evolution law forthe state variable, and we couple the temporal variations of friction coefficient with thoseof effective normal stress. In the companion paper we investigate the effects of thermalpressurization on the dynamic traction evolution. We solve the 1-D heat conductionequation coupled with Darcy’s law for fluid flow in porous media. We obtain a relationthat couples pore fluid pressure to the temperature evolution on the fault plane. Weanalytically solve the thermal pressurization problem by considering an appropriate heatsource for a fault of finite thickness. Our modeling results show that thermal pressurizationreduces the temperature increase caused by frictional heating. However, the effect of theslipping zone thickness on temperature changes is stronger than that of thermalpressurization, at least for a constant porosity model. Pore pressure and effective normalstress evolution affect the dynamic propagation of the earthquake rupture producing ashorter breakdown time and larger breakdown stress drop and rupture velocity. Theevolution of the state variable in the framework of rate- and state-dependent friction lawsis very different when thermal pressurization is active. In this case the evolution of thefriction coefficient differs substantially from that inferred from a slip-weakening law. Thisimplies that the traction evolution and the dynamic parameters are strongly affected bythermal pressurization. http://hdl.handle.net/2122/536 Titolo: Carbon dioxide diffuse degassing and estimation of heat release from volcanic and hydrothermal systems<br/><br/>Autori: Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Granieri, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Avino, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Caliro, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Werner, C.; Institute of Geological and Nuclear Sciences, Taupo, New Zealand<br/><br/>Abstract: We present a reliable methodology to estimate the energy associated with the subaerial diffuse degassing of volcanic-hydrothermal fluids. The fumaroles of 15 diffuse degassing structures (DDSs) located in eight volcanic systems in the world were sampled and analyzed. Furthermore, each area was measured for soil temperature gradients and for soil CO2 fluxes. The results show that each hydrothermal or volcanic system is characterized by a typical source fluid which feeds both the fumaroles and diffuse degassing throughthe soil. Experimental data and the results of physical numerical modeling of the process demonstrate that the heat released by condensation of steam at depth is almost totally transferred by conduction in the uppermost part of the soil. A linear relationship is observed between the log of the steam/gas ratio measured in the fumaroles and the log of the ratio between soil thermal gradient and soil-gas flux. The main parameter controlling this relation is the thermal conductivity of the soil (Kc). For each area, we computed the values of Kc which range from 0.4 to 2.3 W m 1 C 1. Using the CO2 soil fluxes as atracer of the deep fluids, we estimated that the total heat released by steam condensation in the systems considered varies from 1 to 100 MW. http://hdl.handle.net/2122/376 Titolo: Active geodynamics of the central Mediterranean Sea: Tensional tectonic evidences in western Sicily from mantle-derived helium<br/><br/>Autori: Caracausi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Favara, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Italiano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Nuccio, P. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Paonita, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Rizzo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia<br/><br/>Abstract: We report results on the measured high 3He/4Heisotope ratio in western Sicily, interpreted together with the heat data. The study of this sector of the Europe-Africa interaction is crucial to a better understanding of thetectonics and the geodynamical evolution of the central Mediterranean area. The estimated mantle-derived helium fluxes in the investigated areas are up to 2–3 orders of magnitude greater than those of a stable continental area.The highest flux, found in the southernmost area near the Sicily Channel, where recent eruptions of the Ferdinandea Island occurred 20 miles out to sea off Sciacca, has been associated with a clear excess of heat flow. Our results indicate that there is an accumulation of magma below thecontinental crust of western Sicily that is possibly intruding and out-gassing through roughly N-S trending deep fault systems linked to the mantle, that have an extensional component. Although the identification of these faults is notsufficiently constrained by our data, they could possibly be linked to the pre-existing faults that originated during the Mesozoic extensional-transtensional tectonic phases.