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Electrical potential measurement by ocean cable network

通过海洋电缆网络进行电势测量

基本信息

批准号：
06041025
负责人：
UTADA Hisashi
金额：
$ 9.54万
依托单位：
Univ.of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06041025/
关键词：
submarine cable network geomagnetic field variations electrical conductivity structure western Pacific Kuroshio flux induction effect toroidal magnetic field core-mantle boundary secular variations 潮汐変動電位差観測フィリピン海プレート電気伝導度電位差

项目摘要

This three-year project has been carried out for the purpose of constructing a submarine cable network to measure electrical potential variations in the Pacific. For the first and second years, recording systems were installed at the international cable landing stations at Guam, Ninomiya, Okinawa, and Nakhodka. Observations of geomagnetic field variations have been also made at Guam, Vladivostok, and Muntinlupa.Using the data thus obtained, analyzes were carried out to study the electrical conductivity structure of the mantle in the western Pacific region. One-dimensional analysis indicated a presence of a highly conducting layr at about 150 km depth. A thin sheet modeling technique was applied to evaluate the effect of major surface heterogeneity such as ocean-continent distribution.At period range longer than several hours, induction effects by water flow across the cable become dominant in the measured voltage. A study on the time variation in Kuroshio flux has been done by using the cable voltage data between Okinawa and Taiwan where Kuroshio flows into East China Sea through a narrow channel.A simple theoretical work was done to calculate the induction effect on the electromagnetic variations originated from the Earth's core through the conducting mantle. This calculation showed that the electric field variations measured on the Earth's surface includes a component corresponding to the toroidal mode of the geomagnetic field variations which can never be observed by magnetic measurements. The calculation suggested that short term secular variations of a few decades' periods may be observed only by a cable voltage measurement. It also implied that a cable network may reveal not only the intensity but also information on the spatial distribution of the toroidal magnetic field near the core-mantle boundary.

这个为期三年的项目是为了建造一个海底电缆网络，以测量太平洋的电位变化。第一年和第二年，在关岛、二宫、冲绳和纳霍德卡的国际电缆登陆站安装了记录系统。在关岛、海参崴、蒙廷卢帕等地也进行了地磁场变化的观测，并利用这些资料分析研究了西太平洋地区地幔的电导率结构。一维分析表明，在约150公里深处存在一个高导电层。薄片模拟技术被用来评估主要的表面不均匀性的影响，如海洋-大陆的分布。在周期范围超过几个小时，感应效应的水流通过电缆成为占主导地位的测量电压。利用冲绳与台湾之间的电缆电压资料，研究了黑潮通过狭窄通道流入东海时黑潮通量的时间变化，并从理论上计算了地核通过导电地幔时电磁变化的感应效应。这一计算表明，在地球表面测得的电场变化包括一个对应于地磁场变化的环形模式的分量，这是磁测量永远无法观察到的。计算表明，电缆电压的短期长期变化可以观察到几十年的周期，只有电缆电压测量。这也意味着电缆网络不仅可以揭示核幔边界附近环形磁场的强度，还可以揭示其空间分布信息。