Seismological and SAR signature of unrest at Nisyros caldera, Greece

Sachpazi, Maria; Kontoes, Charalampos; Voulgaris, Nicholas; Laigle, Mireille; Vougioukalakis, Georgios C.; Sikioti, Olga; Stavrakakis, G.; Baskoutas, J.; Kalogeras, I.; Lépine, Jean-Claude

doi:10.1016/s0377-0273(01)00334-1

Cited by 44 publications

(37 citation statements)

References 25 publications

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“…Thousands of local, shallow, low magnitude seismic events have been manifested, located mainly in the area between Nisyros and Yali islands, with characteristics that do not permit the discrimination between tectonically and volcanically triggered events. In the same period ground deformation was manifested by the opening of two fractures on North Nisyros and Yali, along active faults previously mapped on land and underwater and by a vertical ground uplift of about 140 mm revealed by SAR interferometry (SACHPAZI et al, 2002). Similar periods of intense seismic activity have been common to the past: It is known that violent seismic shocks accompanied the eruptions of 1871-1873 (GORCEIX, 1873a(GORCEIX, -d, 1874.…”

Section: Past and Recent Seismicity Of Nisyrosmentioning

confidence: 76%

“…At the end of 1995, an intense seismic activity began on the island and lasted for about three years (VOUGIOUKALAKIS et al, 1998;SACHPAZI et al, 2002). Thousands of local, shallow, low magnitude seismic events have been manifested, located mainly in the area between Nisyros and Yali islands, with characteristics that do not permit the discrimination between tectonically and volcanically triggered events.…”

Section: Past and Recent Seismicity Of Nisyrosmentioning

confidence: 99%

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Continuous, Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)

Teschner

Faber

Poggenburg

et al. 2007

Pure appl. geophys.

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In this paper the installation and long-term operation of a system for continuous monitoring of fumarolic gases is described. Several physicochemical and gas-geochemical parameters such as the concentration of CO 2 , H 2 S and CO in the fumarolic emissions, as well as the temperatures of the hydrothermal steam and soil in close vicinity of the fumarole and steam pressure are measured in short-time intervals (typically 15 seconds). Data are logged on-site and in parallel transferred to a remote station by digital telemetry. Specially developed software enables the real-time observation of the local conditions in the crater and full bidirectional control of the monitoring system. Fluctuations in the monitored parameters are also reported. From the data presented it can be concluded that environmental conditions (direction and strength of wind, precipitation) will interact with some of the parameters monitored. These influences can only be revealed by continuously operated monitoring systems.

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Section: Past and Recent Seismicity Of Nisyrosmentioning

confidence: 76%

Section: Past and Recent Seismicity Of Nisyrosmentioning

confidence: 99%

Continuous, Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)

Teschner

Faber

Poggenburg

et al. 2007

Pure appl. geophys.

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“…0.9 km 2 hydrothermal area with fumaroles and mudpools is located in the central southern part of the caldera (known as the Lakki Plain; Figure 1) and has been the locus of at least 13 phreatic eruptions in historical times [Caliro et al, 2005;Hardiman, 1996], the most recent in 1888. A volcano-seismic crisis on Nisyros between 1995 and 1998 was accompanied by 14 cm of ground uplift on the island [Sachpazi et al, 2002]. This episode has not (yet) culminated in an eruption.…”

Section: Observations and Results From Nisyros Calderamentioning

confidence: 99%

On the interpretation of gravity variations in the presence of active hydrothermal systems: Insights from the Nisyros Caldera, Greece

Gottsmann

Rymer

Wooller

2005

Geophysical Research Letters

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[1] We report on short-term (over tens of minutes) residual gravity changes recorded at the restless Nisyros caldera in Greece via a series of discrete measurements at benchmarks within or in proximity to a hydrothermal area located along the caldera floor. The obtained time series reveal sinusoidal gravity variations with amplitudes of up to 25 mGal and wavelengths of 40 -50 min. Degassing of a magmatic source coupling into (shallow) hydrothermal systems including the ascent of steam pockets and transient pressure variations during steam/liquid interface propagation appear to be the most likely causative process for the observed short-term variations. We assess standard protocols of microgravity surveys for hazard assessment in volcanic areas in the light of these findings and propose additional techniques, such as continuous gravimetry, for the discrimination of hydrothermal signals from deeperseated, i.e. magmatic, signals during gravity monitoring of restless volcanoes hosting active hydrothermal systems.Citation: Gottsmann, J., H. Rymer, and L. K. Wooller (2005), On the interpretation of gravity variations in the presence of active hydrothermal systems:

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“…The Stefanos crater was chosen for our study because of a recent increase in fumarole activity and outflow of melted sulfur and hot mud (Papadopoulos et al, 1998;Chiodini et al, 2002;Sachpazi et al, 2002;Vougioukalakis and Fytikas, 2005;Lagios et al, 2007), as well as its strong thermal signature in comparison to other phreatic craters (Lagios et al, 2007;Ganas et al, 2010). Moreover, our results may have implications relevant for other sites.…”

Section: Discussionmentioning

confidence: 95%

“…1). This volcanic island has a long history of phreatic eruptions, the latest in 1871-1873 and 1887 , experiencing an episode of unrest in 1996-2001 (Papadopoulos et al, 1998;Chiodini et al, 2002;Sachpazi et al, 2002). The Stefanos crater is one of several phreatic craters on Nisyros, and is also the major contributor to the total heat budget of the island (Lagios et al, 2007;Ganas et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

Pantaleo

Walter

2014

Solid Earth

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Abstract. Fumarole fields related to hydrothermal processes release the heat of the underground through permeable pathways. Thermal changes, therefore, are likely to depend also on the size and permeability variation of these pathways. There may be different explanations for the observed permeability changes, such as fault control, lithology, weathering/alteration, heterogeneous sediment accumulation/erosion and physical changes of the fluids (e.g., temperature and viscosity). A common difficulty, however, in surface temperature field studies at active volcanoes is that the parameters controlling the ascending routes of fluids are poorly constrained in general. Here we analyze the crater of Stefanos, Nisyros (Greece), and highlight complexities in the spatial pattern of the fumarole field related to permeability conditions. We combine high-resolution infrared mosaics and grain-size analysis of soils, aiming to elaborate parameters controlling the appearance of the fumarole field. We find a ring-shaped thermal field located within the explosion crater, which we interpret to reflect near-surface contrasts of the soil granulometry and volcanotectonic history at depth. We develop a conceptual model of how the ring-shaped thermal field formed at the Stefanos crater and similarly at other volcanic edifices, highlighting the importance of local permeability contrast that may increase or decrease the thermal fluid flux.

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Seismological and SAR signature of unrest at Nisyros caldera, Greece

Cited by 44 publications

References 25 publications

Continuous, Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)

Continuous, Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)

On the interpretation of gravity variations in the presence of active hydrothermal systems: Insights from the Nisyros Caldera, Greece

The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

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