ドーム状隆起に伴う磁場変化 ―有珠山2000 年噴火時の全磁力変化再検討―

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We investigated geomagnetic changes due to dome-like deformation by using a truncatedcircular cone model. In the case of the normal magnetization, magnetic total field decreasesin the northern side of the uplift center, while it increases in the southern side. We foundthat the original topography prior to the mound formation does not affect the pattern of thismagnetic change. We then apply this calculation to the mound-forming activity in the 2000eruption of Usu Volcano to infer the magnetic change on the foot of the mound. The expectedrange of magnetic total field change at the station U01 is -80 to -800 nT which is in theopposite sense to the observed actual change (+70 nT). We examined some alternativemechanisms to compensate this decrease due to the deformation. None of them, however,can be a promising candidate. The most reasonable explanation so far for this contradictionis the reversed magnetization of the Tertiary lava that may comprise the mound.
北海道大学大学院理学研究院自然史科学部門（地球物理学）の論文
2007-03-15