A research of mechanism of electromagnetic radiation associated with crustal activities

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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