Geomagnetic Total Intensity Observation of Izu-Oshima Volcano during 2007-2010
Toshiaki MISHIMA,Yosuke TAGUCHI,Norimichi MASHIKO,Mayumi AKUTAGAWA,Akira YAMAZAKI and Nobuyuki KUMASAKA
Abstract
In order to monitor the volcanic activity of Mt. Mihara, Izu-Oshima, we initiated the continuous observation of the geomagnetic total intensity at Mihara-kita (MIK) site, which is located north of the crater in 1997. We also started the repeated observations of the geomagnetic total intensity at 15 sites around the crater. In this paper we introduce the present observation results until November 2010.
1. The continuous observation record displays annual variations with an amplitude of about 20 nT. The phase of the annual variation is consistent with the ground temperature measured at the site and supposed to be caused by thermal magnetization changes of near-surface rocks. We calculate long-term geomagnetic variation reflecting volcanic activity by subtracting annual variation estimated from ground temperature data. We are studying the ground temperature change to improve the calculation method.
2. We are still in the storing stage of repeated observation records. In this paper we only present the records, although some trends are notable.
(Received 11 November 2010; received in revised form 14 December 2010; accepted 21 December 2010)
