A research of mechanism of electromagnetic radiation associated with crustal activities

这项研究的主要目的是阐明与地壳活动有关的电磁辐射特征，以寻求预测地震或火山喷发的新技术。分析了1985年以来利用美国高知大学和斯坦福大学的ELF/VLF辐射计合作观测获得的ELF/VLF频段自然电磁噪声的连续记录。首次研究了近5年来日本及周边地区电磁异常噪声与大地震和火山喷发的关系。虽然没有探测到明显的前兆电磁辐射，但噪声水平的异常突变有时与有感地震的地面运动同步观察到。不幸的是，很明显，关于电磁波的传播方向和特征的足够信息没有被记录在…的当前记录中由于记录容量的限制，辐射计的G系统较多。为了弥补这一缺陷，我们利用大容量数字音频磁带制作了一套ELF波连续记录系统。此外，我们还研制了一种利用大型不锈钢球体观测电场三分量的非接触式球形天线系统，并在实验室、野外和浅海海底进行了初步实验。其次，我们对哨声和波导模式下的背景电磁脉冲波进行了多种数值模拟，并与观测结果进行了比较。特别是对电磁波在电离层中的传播机制及其时间变化提出了理论解释。此外，我们还研究了在高知观测到的电磁脉冲波与澳大利亚北部位于地磁共轭点的闪电活动之间的关系。最后，我们将上述研究成果总结为科学研究助学金研究项目的一份报告。较少

Main purpose of this study is to clarify characteristics of electromagnetic radiation associated with earth's crustal activities in order to search for a new technique for prediction of earthquake or volcanic eruption. We analyzed continuous records of natural electromagnetic noises in ELF/VLF bands that had been obtained through cooperative observation using ELF/VLF Radiometer conducted by Kochi University and Stanford University, U. S. A., since 1985.We first investigated relationship between anomalous electromagnetic noises and major earthquakes and volcanic eruptions occurred in and around Japan during the past 5 years. Though clear precursory electromagnetic radiation was not detected, anomalous abrupt change of noise level was sometimes observed synchronously with the ground motion of felt earthquake. Unfortunately, it became clear that sufficient information about propagation direction and characteristics of the electromagnetic waves had not been recorded in the present recordin … More g system of the Radiometer because of the limit of recording capacity. To compensate for it we made a continuous recording system for ELF waves using Digital Audio Tape with a large recording capacity. Moreover, we developed a ball antenna system of noncontact type designed for observing three components of electric field using large stainless spheres and made preliminary experiments in a laboratory, field, and shallow sea bottom.Secondly, we executed many kinds of numerical simulations in analyses of background electromagnetic pulse waves in whistler and waveguide modes and then compared with the observed waves. Especially, theoretical interpretations on propagation mechanism of electromagnetic waves in the ionosphere and its time variation were advanced. Moreover, we investigated relationship between electromagnetic pulse wave observed at Kochi and lightening activity at northern Australia that is located at a geomagnetically conjugate point against Kochi.Finally, we summarized above research results as a Report of Research Project, Grant-in-Aid for Scientific Research. Less