Relations between electrical resistivity, carbon dioxide flux, and self-potential in the shallow hydrothermal system of Solfatara (Phlegrean Fields, Italy)

Byrdina, Svetlana; Vandemeulebrouck, Jean; Cardellini, Carlo; Legaz, A.; Camerlynck, Christian; Chiodini, Giovanni; Lebourg, Thomas; Gresse, Marceau; Bascou, Pascale; Motos, Ghislan; Carrier, Aurore; Caliro, Stefano

doi:10.1016/j.jvolgeores.2014.07.010

Cited by 61 publications

(60 citation statements)

References 35 publications

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“…The depth range, for which the variations in velocity are depicted, coincides with the interface of gas-dominated reservoirs overlain by shallow conductive bodies interpreted as aquifers filled by condensate (e.g. Petrillo et al 2013;Byrdina et al 2014).…”

Section: N O I S E -B a S E D 4 -D M O N I T O R I N G O F V E L O C mentioning

confidence: 77%

“…The comparison between the spatial variability of resistivity and gas flux emphasized a highly resistive body indicating that resistivity changes at this depth are related to high temperature gas saturation (Byrdina et al 2014). Further evidence of a gas fluid reservoir comes from recent seismic attenuation imaging, recognizing a vertically extending, high attenuation structure (De Siena et al 2010).…”

Section: Discussionmentioning

confidence: 95%

“…The central Solfatara area around the Fangaia mud pool, corresponding to lowest surface temperatures (Letort et al 2012;Byrdina et al 2014), is characterized by a significant velocity increase for depths larger than 25 m. In parallel, an increase of the v P /v S ratio can be found. This central zone can be interpreted as a mechanically soft and liquid-saturated part of the hydrothermal system, as compared to the drier and hotter zones in the eastern and northwestern sector of the study area.…”

Section: Discussionmentioning

confidence: 96%

“…8) delineate a distinct liquiddominated conductive plume below the Fangaia mud pool. Such a highly conductive layer might be interpreted as an aquifer saturated with hot water condensing from a gas reservoir below (Byrdina et al 2014). The aquifer is anomalously shallow for the water table height and the water temperature.…”

Section: Discussionmentioning

confidence: 99%

“…These systems crosscut the study area and have been active several times in the past. The geophysical structure below the Solfatara area has been investigated on various spatial scales using different geophysical methods like gravity, electric resistivity and thermal imaging (Petrosino et al 2006(Petrosino et al , 2012Bruno et al 2007;Letort et al 2012;Byrdina et al 2014;Vilardo et al 2015). Recently, Serra et al (2016) investigated the shallow structure of a small part of the Solfatara crater using active seismic methods but their penetration depth was limited to 15 m.…”

Section: T H E S O L Fata R a C R At E R : C H A R A C T E R I S T I mentioning

confidence: 99%

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A 3D algorithm based on the combined inversion of Rayleigh and Love waves for imaging and monitoring of shallow structures

2017

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S U M M A R YIn recent years, there has been increasing interest in the study of seismic noise interferometry as it can provide a complementary approach to active source or earthquake-based methods for imaging and continuous monitoring the shallow structure of the Earth. This meaningful information is extracted from wavefields propagating between those receiver positions at which seismic noise was recorded. Until recently, noise-based imaging relied mostly on Rayleigh waves. However, considering similar wavelengths, a combined use of Rayleigh and Love wave tomography can succeed in retrieving velocity heterogeneities at depth due to their different sensitivity kernels. Here, we present a novel one-step algorithm for simultaneously inverting Rayleigh and Love wave dispersion data aiming at identifying and describing complex 3-D velocity structures. The algorithm may help to accurately and efficiently map the shear wave velocities and the Poisson ratio of the surficial soil layers. In the high-frequency range, the scattered part of the correlation functions stabilizes sufficiently fast to provide a reliable estimate of the velocity structure not only for imaging purposes but also allows for changes in the medium properties to be monitored. Such monitoring can be achieved with a high spatial resolution in 3-D and with a time resolution as small as a few hours. In this paper, we describe a recent array experiment in a volcanic environment in Solfatara (Italy) and we show that this novel approach has identified strong velocity variations at the interface between liquids and gas-dominated reservoirs, allowing localizing a region which is highly dynamic due to the interaction between the deep convection and its surroundings.

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Section: N O I S E -B a S E D 4 -D M O N I T O R I N G O F V E L O C mentioning

confidence: 77%

Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: T H E S O L Fata R a C R At E R : C H A R A C T E R I S T I mentioning

confidence: 99%

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A 3D algorithm based on the combined inversion of Rayleigh and Love waves for imaging and monitoring of shallow structures

2017

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A geochemical and geophysical reappraisal to the significance of the recent unrest at Campi Flegrei caldera (Southern Italy)

Moretti

Natale

Troise

2017

Geochem Geophys Geosyst

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Volcanic unrest at calderas involves complex interaction between magma, hydrothermal fluids, and crustal stress and strain. Campi Flegrei caldera (CFc), located in the Naples (Italy) area and characterized by the highest volcanic risk on Earth for the extreme urbanization, undergoes unrest phenomena involving several meters of uplift and intense shallow microseismicity since several decades. Despite unrest episodes display in the last decade only moderate ground deformation and seismicity, current interpretations of geochemical data point to a highly pressurized hydrothermal system. We show that at CFc, the usual assumption of vapor‐liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and, accordingly, interpretations of elevated unrest. By relaxing unconstrained geochemical assumptions, we infer an alternative model yielding better agreement between geophysical and geochemical observations. The model reconciles discrepancies between what observed (1) for two decades since the 1982–1984 large unrest, when shallow magma was supplying heat and fluids to the hydrothermal system, and (2) in the last decade. Compared to the 1980's unrest, the post‐2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement, as indicated by geophysical data and despite large changes in geochemical indicators. Our interpretation points out a model in which shallow sills, intruded during 1969–1984, have completely cooled, so that fumarole emissions are affected now by deeper, CO2‐richer, magmatic gases producing the modest heating and overpressure of the hydrothermal system. Our results have important implications on the short‐term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data.

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Geophysical imaging of shallow degassing in a Yellowstone hydrothermal system

Pasquet

Holbrook

Carr

et al. 2016

Geophysical Research Letters

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The Yellowstone Plateau Volcanic Field, which hosts over 10,000 thermal features, is the world's largest active continental hydrothermal system, yet very little is known about the shallow “plumbing” system connecting hydrothermal reservoirs to surface features. Here we present the results of geophysical investigations of shallow hydrothermal degassing in Yellowstone. We measured electrical resistivity, compressional‐wave velocity from refraction data, and shear wave velocity from surface‐wave analysis to image shallow hydrothermal degassing to depths of 15–30 m. We find that resistivity helps identify fluid pathways and that Poisson's ratio shows good sensitivity to saturation variations, highlighting gas‐saturated areas and the local water table. Porosity and saturation predicted from rock physics modeling provide critical insight to estimate the fluid phase separation depth and understand the structure of hydrothermal systems. Finally, our results show that Poisson's ratio can effectively discriminate gas‐ from water‐saturated zones in hydrothermal systems.

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Relations between electrical resistivity, carbon dioxide flux, and self-potential in the shallow hydrothermal system of Solfatara (Phlegrean Fields, Italy)

Cited by 61 publications

References 35 publications

A 3D algorithm based on the combined inversion of Rayleigh and Love waves for imaging and monitoring of shallow structures

A 3D algorithm based on the combined inversion of Rayleigh and Love waves for imaging and monitoring of shallow structures

A geochemical and geophysical reappraisal to the significance of the recent unrest at Campi Flegrei caldera (Southern Italy)

Geophysical imaging of shallow degassing in a Yellowstone hydrothermal system

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