| 講演要旨(和文) | | 2015年1月SIP研究の一環として（一社）海洋調査協会は、伊豆小笠原弧の西縁に位置するベヨネース海丘（火山）周辺海域において海上からの地磁気および地形調査と、さらに本火山カルデラ域を対象に深度200m~500mでディープ・トウによる地磁気、SSS、SBP調査を実施した。このカルデラ内には熱水鉱床（白嶺鉱床）の存在が知られている。海上およびディープ・トウによって得られた地磁気データから、本火山の3次元磁化構造を求めた。それによると火山体の下部はおよそ6A/m以上の強磁性岩体で構成されるのに対し、上部はほぼ1A/m前後の低い値を示すものの一部2~3A/mのやや高い個所が点在する。またカルデラ内の中央火口丘および白嶺鉱床部は1A/m以下の値を示す。 |
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| | 講演要旨(英文) | | Total geomagnetic and topographic surveys in and around the Beyonnaise knoll volcano, which is located on the western margin of active arc (volcanic front), Izu-Ogasawara island arc, were conducted by Japan Marine Surveys Association (JAMSA) as a part of SIP in January, 2015. The geomagnetism was investigated by using a sea surface ship and a deep-tow which was towed between the depths from 200 m to 500 m. The topography was surveyed by a multi-beam echo sounder (MBES) from the sea surface ship. The 3-D magnetic inversion study revealed that the lower part of the Beyonnaise Knoll was composed of a high magnetization more than 6 A/m. The upper part was composed of weak-magnetization (around 1 A/m) for the most part, but a relatively strong part (2~3 A/m) was interspersed among the weakness. And it was also shown that the magnetizations of the central cone and a large hydrothermal deposit (Hakurei thermal deposit) were very low (less than 1 A/m). |
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