CSAMT measurements across the 1986 C craters of Izu-Oshima Island, Japan.
CSAMT measurements across the 1986 C craters of Izu-Oshima Island, Japan.
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1986 年日本伊豆大岛 CSAMT 陨石坑的测量。
DOI：
10.5636/jgg.42.211
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
S. Takakura
中科院分区：
文献类型：
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作者：
Y. Ogawa;S. Takakura
我们进行了CSAMT（可控源音频大地电磁）测量整个1986年C火山口的伊豆大岛爆发后一年。在对两个剖面进行二维分析后，除了浅层电阻率变化外，我们基本上得到了两层结构。与附近的威尔斯井相比，我们在电阻性熔岩下面发现了一个对应于热水的深导电层。我们还发现了浅（<200米）的导电体，其位置对应于一个古老的喷口（世纪）和1986年的一个陨石坑。我们认为这些断裂带含有大气降水。我们没有得到脉状构造的肯定证据，部分原因是我们使用了TM模式激发，部分原因是脉没有向周围岩石传递足够的热量以降低电阻率。我们认为这三层对应于（顶部）电阻性熔岩、（中间）淡水透镜和（底部）海水。我们认为这两个剖面缺乏淡水透镜，这是由于热对流造成淡水和盐水的混合。
We carried out CSAMT (controlled-source audiofrequency magnetotelluric) measurements across the 1986 C craters of Izu-Oshima Island one year after the eruptions. After 2D analyses of the two profiles, we obtained basically two-layered structures, except for shallow resistivity variations. We found a deep conductive layer below the resistive lava which corresponds to thermal water, compared with nearby wells. We also found shallow (<200m) conductive bodies whose locations correspond to an old vent (8th century) and one of the 1986 craters. We think these are fracture zones containing meteoric water. We did not get affirmative evidence for dyke-like structures, partly because we used TM mode excitation, and partly because the dyke hadn't transferred enough heat to the surrounding rocks to decrease resistivity.Away from the profiles, we found a three layered structure. We think the three layers correspond to (top) resistive lava, (middle) a fresh water lens, and (bottom) sea water. We think the two profiles lacked the fresh water lens due to mixing of fresh and saline water by thermal convection.