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Title: 有珠山自然電位観測2006
Other Titles: Self-potential Survey on Usu Volcano, 2006 Campaign
Authors: 長谷, 英彰1 Browse this author
橋本, 武志2 Browse this author
西田, 泰典3 Browse this author
宇津木, 充4 Browse this author
井上, 寛之5 Browse this author
佐波, 瑞恵6 Browse this author
Authors(alt): HASE, Hideaki1
NISHIDA, Yasunori3
UTSUGI, Mitsuru4
INOUE, Hiroyuki5
SABA, Mizue6
Issue Date: 15-Mar-2007
Publisher: 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)
Journal Title: 北海道大学地球物理学研究報告
Journal Title(alt): Geophysical bulletin of Hokkaido University
Volume: 70
Start Page: 43
End Page: 52
Abstract: We conducted self-potential (SP) surveys on Usu volcano since July to December 2006. The compiled SP map reveals positive anomalies around Ko-Usu lava dome and at the foot of the volcano, and a negative anomaly on the top of O-Usu lava dome. The SP profile on the summit caldera shows the same pattern of 1985’s. However, the peak-to-peak variation of the SP value is different: the 1985’s of that shows 1000 mV while the 2006’s shows 1400 mV. Topographic effect is clearly shown along the southwestern foot of the volcano, in which coefficient is about -2.5 mV/m. The SP profile corrected of the topographic effect reveals a large and extensive positive anomaly over +600mV and several local positive anomalies over +1000 mV on the summit caldera. The corrected SP also reveals that a positive anomaly at the south part of Ko-Usu lava dome and a negative anomaly at the O-Usu lava dome do not exist. The revealed positive SP anomalies are likely to be affected by an extensive altered layer, located beneath the summit caldera. The largest positive anomaly is shown on the ridge of Usu-Shinzan cryptodome after topographic correction. This anomaly is not regarded to be formed by hydrothermal upwelling, because any indications of fumarolic and geothermal activities have not been observed on the ridge of the volcano. The SP anomaly may be affected by intruded material into the volcano. The SP amplitude in the northwestern part of Nishiyama is very small in spite of rugged topography. An extensive low resistivity layer (< 10 ohm-m) located in the shallow part in the northwestern of Nishiyama probably shields the SP variation.
Type: bulletin (article)
Appears in Collections:北海道大学地球物理学研究報告 = Geophysical bulletin of Hokkaido University > 第70号

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