Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/3513
AuthorsSaba, M.* 
Nishida, Y.* 
Takakura, S.* 
Matsushima, N.* 
Mogi, T.* 
TitleDevelopment of geothermal field following the 2000 eruption of Usu volcano as revealed by ground temperature, resistivity and self-potential variations
Issue DateFeb-2007
Series/Report no.1/50 (2007)
URIhttp://hdl.handle.net/2122/3513
KeywordsUsu volcano
geothermal field
ground temperature
electrical prospecting
selfpotential field
hydrothermal circulation
Subject Classification04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring 
AbstractThe 2000 eruption of Usu volcano, NE Japan, took place on the foot of the somma, and formed a cryptodome of 65 m high accompanying numerous faults. We made repeated measurements of ground temperature, Self-Potential (SP) and electrical resistivity, in order to clarify the mechanism of development of the newly formed geothermal field on the fault zone. Prior to the expansion of the geothermal field, we detected a resistive zone at the center of the geothermal zone and it supposed to evidence that the zone involving dry steam phase had been formed beneath the fault zone. A rapid expansion of the geothermal field followed along the fault zone away from the craters. The place of maximum amplitude of the SP field also migrated following the expansion of the high ground temperature zone. The high resistive part has shrunk as a consequence of the progress of condensation to warm the surroundings. Based on the observations, we delineated the process of the hydrothermal circulation. Considering the topographic effect of the SP field observed on the highly permeable zone in the Usu somma, the potential flow along the slope of the soma was expected to play an important role to promote the rapid expansion of the geothermal field and the migration of the most active part.
Appears in Collections:Annals of Geophysics

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