A 3D Magnetic Structure Of Izu-Oshima Volcano And Their Changes After The Eruption In 1986 As Estimated From Repeated Airborne Magnetic Surveys

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Journal Article: A 3D Magnetic Structure Of Izu-Oshima Volcano And Their Changes After The Eruption In 1986 As Estimated From Repeated Airborne Magnetic Surveys

Abstract
A 3D magnetic inversion method using a conjugate gradient method (CG method) was developed for constructing 3D magnetization models of a volcanic edifice and applied to aeromagnetic anomalies of Izu-Oshima Volcano surveyed in 1986 and in 1997. The calculated results of the 1986 data show that the volcanic edifice of Izu-Oshima Volcano has a mean magnetization intensity ranging from 10.4 to 12.1 A/m. The derived 3D magnetic structure shows low magnetization zones beneath the west-northwest of the western caldera rim, beneath the west-southwest of Mt. Mihara and beneath Mt. Shiroishi. These features may be related with demagnetizations, reflecting a high thermal state due to magma activities in the 1986 eruption. The comparison between 3D magnetization models in 1986 and in 1997, indicates meaningful changes beneath the C-craters erupted in 1986, suggesting a recovery process of demagnetizations and a considerable decrease of magnetization intensities in the foot of Mt. Futago, indicative of demagnetizations. A derived magnetization model including Izu-Oshima Volcano and its surrounding sea areas clarifies the submerged volcanic edifices around Izu-Oshima Island, and suggests that the old volcanic edifices of Fudeshima, Gyojyanoiwaya, and Okata Volcanoes have been affected by eastward migrations due to massive intrusions of a dike-like structure inferred at the base of Izu-Oshima Volcano.

Author 
Yoshio Ueda








Published Journal 
Journal of Volcanology and Geothermal Research, 2007





DOI 
Not Provided
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Citation

Yoshio Ueda. 2007. A 3D Magnetic Structure Of Izu-Oshima Volcano And Their Changes After The Eruption In 1986 As Estimated From Repeated Airborne Magnetic Surveys. Journal of Volcanology and Geothermal Research. (!) .