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| | Abstract | | VLF-EM method has been used for detecting subsurface resistivity anomalies. However, because the source that has been used for the method is unstable, the VLF method is not so widespread. Since about a decade ago, JJY which is more stable than VLF has been used to broadcast the standard Japanese time, so that it would be more suitable for the exploration of underground structure. By using radio time-signal receivers, we can quickly record continuous time signals to estimate the resistivity distribution of subsurface ground wherever in Japan. In our study, we applied numerical experiments to reveal the characteristic of subsurface exploration using JJY. Using electromagnetic wave of 20 kHz as an existing VLF wave and 40 and 60 kHz as JJY standard electromagnetic waves, we evaluated the sensitivity in shallow subsurface resistivity anomalies using numerical method. We also evaluated the influence of angle between strike of an elongated resistivity anomalies and the propagation direction of radio waves. In addition, by applying the Fraser filter, when the model is simple, we obtain a rough resistivity profile of the underground according to magnetic field strength obtained by the numerical calculation. Moreover, we also confirmed that we receive the JJY electric wave for real data analysis. |
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