Numerical modeling of a hydrothermal system around Waita volcano, Kyushu, Japan, based on resistivity and self-potential survey results

Yasukawa, Kasumi; Mogi, Tohru; Widarto, Djedi S.; Ehara, Sachio

doi:10.1016/s0375-6505(02)00048-2

Cited by 24 publications

(9 citation statements)

References 13 publications

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“…We propose here an interpretation of the self‐potential anomalies in relation to the CO 2 flux anomalies and the resistivity tomograms. Because resistivity influences the distribution of the electrical equipotential lines, it is important to incorporate a reasonably accurate resistivity model inside any modeling of the self‐potential response associated with the flow of the groundwater [ Yasukawa et al , 2003; Aizawa et al , 2005; Uyeshima , 2007]. The accurate gas flux and resistivity data are available at the ERTb profile passing perpendicular to cliffs seen in Figure 2.…”

Section: Modeling and Discussionmentioning

confidence: 99%

Dipolar self‐potential anomaly associated with carbon dioxide and radon flux at Syabru‐Bensi hot springs in central Nepal

et al. 2009

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[1] The Syabru-Bensi hot springs are located at the Main Central Thrust (MCT) zone in central Nepal. High carbon dioxide and radon exhalation fluxes (reaching 19 kg m À2 d À1and 5 Bq m À2 s À1, respectively) are associated with these hot springs, making this site a promising case to study the relationship between self-potential and fluids (gas and water) exhalation along a fault zone. A high-resolution self-potential map, covering an area of 100 m by 150 m that surrounds the main gas and water discharge spots, exhibits a dipolar self-potential anomaly with a negative peak reaching À180 mV at the main gas discharge spot. The positive lobe of the anomaly reaching 120 mV is located along the terraces above the main gas and water discharge spots. Several electrical resistivity tomograms were performed in this area. The resistivity tomogram crossing the degassing area shows a dipping resistive channel interpreted as a fracture zone channeling the gas and the hot water. We propose a numerical finite difference model to simulate the flow pattern in this area with the constraints imposed by the electrical resistivity tomograms, the self-potential data, the position of the gas vents, and hot water discharge area. This study provides insights on the generation of electrical currents associated with geothermal circulation in a geodynamically active area, a necessary prerequisite to study, using self-potentials, a possible modulation of the geothermal circulation by tectonic activity.

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Section: Modeling and Discussionmentioning

confidence: 99%

Dipolar self‐potential anomaly associated with carbon dioxide and radon flux at Syabru‐Bensi hot springs in central Nepal

et al. 2009

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“…Generally negative SP anomaly of magnitude 300 mV to 800 mV is observed over sulphide mineralization (TELFORD, 1976). Positive SP anomalies (up to 150 mV) generally suggest upflow of the hot water in the area (CAGLER and DEMIRORER, 1999;YASUKAWA et al, 2003). Smaller magnitude positive SP anomaly is associated with the streaming potential and suggests a lateral flow of groundwater (POZDNYAKOVA et al, 2001).…”

Section: (C) Magnetic Surveymentioning

confidence: 98%

“…Use of these methods in characterization of thermal reservoir is well documented in the literature (BENSON et al, 1997;ZLOTNICKI et al, 1998;CAGLER and DEMIRORER, 1999;MAJUMDAR et al, 2000;SAVIN et al, 2001;RASHED et al, 2003;YASUKAWA et al, 2003). Geothermal reservoir's steam, water or heat can be used for electricity generation and other commercial purposes.…”

Section: Introductionmentioning

confidence: 99%

Integrated Geophysical Studies in the East-Indian Geothermal Province

Baranwal

Sharma

2006

Pure appl. geophys.

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Integrated geophysical surveys using vertical electrical sounding (VES), very low frequency (VLF) EM, radiation counting, total magnetic field and self-potential (SP) measurements are carried out to characterize the geothermal area around a hot spring in the Nayagarh district, Orissa, India that lies in the East Indian geothermal province. The study was performed to delineate the fracture pattern, contaminated groundwater movement and possible heating source. VES interpretations suggest a three-to four-layer structure in the area. Resistivity survey near the hot spring suggests that weathered and fractured formations constitute the main aquifer system and extend to 60 m depth. Current flow measured at various electrode separations normalized by the applied voltage suggests that fractures extend to a greater depth. Detailed VLF study shows that fractures extend beyond 70 m depth. VLF anomaly has also very good correlation with the total magnetic field measured along the same profiles. Study results suggest that a gridded pattern of VLF survey could map the underground conductive fracture zones that can identify the movement of contaminated groundwater flow. Therefore, precautionary measures can be taken to check further contamination by delineating subsurface conducting structures. Self potential (SP) measured over the hot spring does not show a large anomaly in favor of the presence of a sulphide mineral body. A small positive (5-15mV) SP anomaly is measured which may be streaming potential due to subsurface fluid flow. A high radiation is measured about four kilometers from the hot spring, suggesting possible radiogenic heating. However, the exact nature of the heating source and its depth is not known in the area. Deep resistivity followed by a magneto-telluric survey could reveal the deeper structures.

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“…Especially in shallow areas in geothermal fields, self-potential caused by the crosscoupling from temperature, pressure and density contrasts, can be resolved by heat conduction and convection together (NOURBEHECHT, 1963;YASUKAWA 1993;YASUKAWA, et al, 2003).…”

Section: Sp Models Generated From a Thermo-electric Source Relationshmentioning

confidence: 99%

Application of Normalized Full Gradient Method to Self Potential (SP) Data

Sindirgi

Pamukçu

Özyalın

2008

Pure Appl. Geophys.

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Recently, Normalized Full Gradient (NFG) method has widespread applications to natural potential fields, especially in gravity and magnetic. In this study, usage of NFG in Self-Potential (SP) data evaluation is tested. Results are compared to other SP interpretation methods. The NFG method is applied to synthetic and field SP data. As a consequence of application of the method to the anomalies of spherical, cylindrical and vertical sheet models, whose theoretical structures are explicit, the structures were found very close to their actual locations. In order to see the capability of the method in detecting the number of sources, NFG method was applied to different spherical models at different depths and locations. The least-squares inverse solution was applied to the same models and NFG method was found more powerful in detecting model structure. Sensitivity of NFG method for application to noisy data is also tested. An anomaly is generated by adding a random noise to two close sphere SP anomalies. The method seems to work for the two close spheres at high S/N ratio. Then, NFG method was applied to two field examples. The first one is the cross section taken from the SP anomaly map of the Ergani-Süleymanköy (Turkey) copper mine. The depth of the mineral deposit at that site was found about 38 m from the ground level. This result is well matched to previous studies. NFG was also applied to SP data from Seferihisar Izmir (Western Turkey) geothermal field and the location of the point source was determined. The field data of this site have already been modeled by the thermoelectric source (coupling) solution method. When these two methods are compared, they seem to support each other. It is concluded that the NFG method works perfectly when the structure model is simple. It is observed that natural potential sources close to earth's surface are identified by the method more accurately at greater harmonics, while deep sources are identified at lesser harmonics. It produces reasonable results for noisy multi-source models than the other parameter identification methods (inverse solution, power spectrum, etc.).

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Numerical modeling of a hydrothermal system around Waita volcano, Kyushu, Japan, based on resistivity and self-potential survey results

Cited by 24 publications

References 13 publications

Dipolar self‐potential anomaly associated with carbon dioxide and radon flux at Syabru‐Bensi hot springs in central Nepal

Dipolar self‐potential anomaly associated with carbon dioxide and radon flux at Syabru‐Bensi hot springs in central Nepal

Integrated Geophysical Studies in the East-Indian Geothermal Province

Application of Normalized Full Gradient Method to Self Potential (SP) Data

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