Study on continuous electromagnetic surveys precisely controlled of frequency. Annual report on the field of advancing basic technology in 1996 fiscal year

This study aims at research and development of a system to control on high precision frequency of electromagnetic energy changing in tangential wave and to send it to underground continuously for long time, on geophysical investigation to analyze underground structure due to observation of underground response to it. By adopting this system, expansion of investigation depth, upgrading of analytical accuracy and miniaturization of investigation appliance were aimed. In 1996 fiscal year, in order to understand features of electromagnetic phenomenon over a wide range, a method to measure underground response to analyze its structure due to electromagnetic induction phenomenon by using comparative low frequency range of some tens Hz to some KHz at transmission frequency and a method to detect micro structure (for example crack, and so on) from transmittance and reflection phenomena by using comparatively high frequency range of some tens MHz to some GHz were investigated by using computer simulation. (G.K.)