Hydrothermal system beneath Mt. Fuji volcano inferred from magnetotellurics and electric self-potential

Aizawa, Katsuo; Yoshimura, Ryokei; Oshiman, Naoto; Yamazaki, Katuo; Uto, Tomofumi; Ogawa, Yasuo; Tank, Sabri Bülent; Kanda, Wataru; Sakanaka, Shin’ya; Furukawa, Yohtaro

doi:10.1016/j.epsl.2005.03.023

Cited by 61 publications

(42 citation statements)

References 32 publications

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“…Thus the region of high conductivity beneath the summit acts as a conduit from the region of high potential at depth to the surface. Indeed conductive regions are found just beneath almost all volcano summits Revil et al 2004;Hase et al 2005;Aizawa et al 2005). As an example, Fig.…”

Section: Electric Polarizationmentioning

confidence: 98%

EM Monitoring of Crustal Processes Including the Use of the Network-MT Observations

Uyeshima

2007

Surv Geophys

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There are several kinds of coupling mechanisms which can convert mechanical, chemical or thermal energies due to seismic or volcanic activities into electromagnetic energies. As a result of concentrated efforts in laboratory and theoretical research, the basic relationship between the intensity of electromagnetic sources and changes in mechanical, chemical and thermal state is becoming established. Also with the progress of the electromagnetic simulation techniques, it has been possible to evaluate in situ sensitivity. Based on this progress and also due to extensive improvement in measuring techniques, many field experiments have been performed to elucidate subsurface geophysical processes underlying the preparation stage, onset, and subsequent healing stage of earthquakes and volcanic eruptions. In volcanic studies, many studies have reported the measurement of electromagnetic signals which were successfully interpreted in terms of various driving mechanisms. Although there have been numerous reports about the existence of precursory electromagnetic signals in seismic studies, only a few of them could be successfully explained by the proposed mechanisms, whereas coseismic phenomena are often consistent with those mechanisms including the absence of detectable signals. In many cases, one or two orders of higher sensitivity were required, especially for precursory signals. Generally, electromagnetic methods are more sensitive to near-surface phenomena. It will be necessary to discriminate electromagnetic signals due to these near-surface sources, which often possess no relationship with the crustal activities. Further efforts to enhance in situ sensitivity through improvements in observation techniques and in data processing techniques are recommended. At the same time, multi-disciplinary confirmation against the validity of electromagnetic phenomena will inevitably be necessary. A Network-MT observation technique has been developed to determine large-scale deep electrical conductivity structure. In the method, a telephone line network or purpose-built long baseline cables are utilized to measure voltage differences with long electrode separations. Because of the averaging effect of the electric fields, static shift problems due to small-scale, nearsurface lateral heterogeneities can be alleviated. Several field experiments revealed regional scale deep electrical conductivity structures related to slab subduction or its M. Uyeshima (stagnation, which enable us to elucidate underlying physical processes caused by the slab motion. The technique can also be applied to monitor the electric potential field related to crustal activities. The annual variation of the potential field and electrical conductivity in the French Alps were interpreted to be caused by the annual variation of lake water level. The method was also used to monitor the regional scale spatio-temporal variation of the SP field and electrical conductivity before and at the onset of earthquakes and volcanic eruptions.

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Section: Electric Polarizationmentioning

confidence: 98%

EM Monitoring of Crustal Processes Including the Use of the Network-MT Observations

Uyeshima

2007

Surv Geophys

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“…We use natural electromagnetic fields in the frequency range between 10 KHz and 1 Hz. Electromagnetic methods are widely used for the imaging of active volcanoes because the resistivity is sensitive to the fluids and the clay alteration minerals (Ogawa and Takakura, 1990;Ogawa et al, 1992Ogawa et al, , 1998Ogawa et al, , 1999Pellerin et al, 1996;Di Maio et al, 1998;Kagiyama et al, 1999;Fuji-ta et al, 1999;Matsushima et al, 2001;Müller and Haak, 2004;Ç aglar andİşseven, 2004;Manzella et al, 2004;Oskooi et al, 2005;Aizawa et al, 2005). It must be noted, however, that the interpretation of the conductors as either fluids or clay minerals can lead to opposing conclusions on the hydrology because fluids require high permeability whereas clay alterations may imply low permeability.…”

Section: Introductionmentioning

confidence: 99%

Two electrical conductors beneath Kusatsu-Shirane volcano, Japan, imaged by audiomagnetotellurics, and their implications for the hydrothermal system

et al. 2006

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Kusatsu-Shirane volcano, Japan, is known for its active phreatic eruptions. We have investigated its hydrothermal system by conducting audio-magnetotelluric soundings at 22 stations along a profile that extends across the volcano. The final two-dimensional model is characterized by two conductors. One is a 300-to 1000-m-thick conductor of 1-10 m, which is located on the eastern slope and covered with 200-m-thick resistive layers of Kusatsu-Shirane lava and pyroclastics. This conductor indicates the presence of a Montmorillonite-rich layer of Pliocene volcanic rocks that may function both as an impermeable floor for the shallow fluid path from the peak to the hot springs to the east and as an impermeable cap for the deeper fluid path from the summit region to the foot of the volcano. The second conductor is found at a depth of 1-2 km from the surface, at the peak of the volcano, and its resistivity is as low as 1 m or less. This low resistivity can be explained by fluids containing high concentrations of chloride and sulfate which were supplied from the magmatic gases. Micro-earthquakes cluster above this conductor, and the cut-off of the earthquakes corresponds to the top of the conductor. This conductor infers the presence of the fluid reservoir, and the upward release of these fluids from the reservoir through the conduit presumably triggers the micro-earthquakes at the peak area of the volcano. Crustal deformation modeling using GPS and leveling data of the past 10 years revealed that the center of the deflation coincides with the top of the second conductor, indicating that the fluid reservoir itself can be hosting the deformation.

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“…If the theory that describes the mechanism were known, it would be possible to calculate the permeability of a rock from an electrical measurement without recourse to empirical data fitting as in Glover et al (2006). Furthermore, because electrical parameters can be measured remotely by selfpotential (Ishido and Mizutani, 1981;Antraygues and Aubert, 1993;Revil et al, 2003) (magneto-)telluric (Svetov et al, 1997;Aizawa et al, 2005;Ingham et al, 2009) and GPR techniques (Dupuis et al, 2007), these data may be used to calculate regional or local fluid flow Sailhac and Marquis, 2001;Trique et al, 2002;, or even caused by the redox conditions inside the contaminant plume in a groundwater system (Naudet et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Already, self-potential measurements have been used to map (1) the convective flow of fluids around volcanoes using electrokinetic coupling (e.g., Revil et al, 2003;Aizawa et al, 2005), (2) the encroachment of water into a hydrocarbon reservoir (Saunders et al, 2008;Jaafar et al, 2009), and (3) in the characterization of subsurface aquifers (Dupuis and Butler, 2006;Dupuis et al, 2009). The same approach may be used to monitor the depletion of a waterdriven reservoir (Fagerlund and Heinson, 2003;Titov et al, 2005;Revil et al, 2003), in geothermal reservoirs (Corwin et al, 1981; or the sudden flow of water into a previously dormant but potentially seismically active fault prior to an earthquake (Mizutani et al, 1976;Di Maio and Patella, 1991;Probstein and Hicks, 1993;Ishido and Pritchett, 1999).…”

Section: Introductionmentioning

confidence: 99%

Streaming-potential coefficient of reservoir rock: A theoretical model

2012

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The streaming potential is that electrical potential which develops when an ionic fluid flows through the pores of a rock. It is an old concept that is recently being applied in many fields from monitoring water fronts in oil reservoirs to understanding the mechanisms behind synthetic earthquakes. We have carried out fundamental theoretical modeling of the streaming-potential coefficient as a function of pore fluid salinity, pH, and temperature by modifying the HS equation for use with porous rocks and using input parameters from established fundamental theory (the Debye screening length, the Stern-plane potential, the zeta potential, and the surface conductance). The model also requires the density, electrical conductivity, relative electric permittivity and dynamic viscosity of the bulk fluid, for which empirical models are used so that the temperature of the model may be varied. These parameters are then combined with parameters that describe the rock microstructure. The resulting theoretical values have been compared with a compilation of data for siliceous materials comprising 290 streaming-potential coefficient measurements and 269 zeta-potential measurements obtained experimentally for 17 matrix-fluid combinations (e.g., sandstone saturated with KCl), using data from 29 publications. The theoretical model was found to ably describe the main features of the data, whether taken together or on a sample by sample basis. The low-salinity regime was found to be controlled by surface conduction and rock microstructure, and was sensitive to changes in porosity, cementation exponent, formation factor, grain size, pore size and pore throat size as well as specific surface conductivity. The high-salinity regime was found to be subject to a zeta-potential offset that allows the streaming-potential coefficient to remain significant even as the saturation limit is approached.

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Hydrothermal system beneath Mt. Fuji volcano inferred from magnetotellurics and electric self-potential

Cited by 61 publications

References 32 publications

EM Monitoring of Crustal Processes Including the Use of the Network-MT Observations

EM Monitoring of Crustal Processes Including the Use of the Network-MT Observations

Two electrical conductors beneath Kusatsu-Shirane volcano, Japan, imaged by audiomagnetotellurics, and their implications for the hydrothermal system

Streaming-potential coefficient of reservoir rock: A theoretical model

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