The Basic Principle and Detector of Applying Abnormal Changes of the Group Delay Difference of EM Waves to Short-Term and Imminent Earthquake Forecast
Abstract: The group delay difference (time difference) between two electromagnetic signals at a given fre-quency, which are located along the same vertical line but at different depths and reach the ground, depends only on the electric conductivity and the thickness of the strata. It is believed that the conductivity of the deep layer undergoes abnormal variations just before earthquakes. Such conductivity variations can be detected in terms of the abnormal changes of the group delay dif-ference, and thus the abnormal changes of the group delay difference may be used for short-term and imminent earthquake prediction. Based on this idea, we have developed an electric field de-tector and a magnetic field detector. The regular alternating signal of 50 Hz is treated as a carrier wave so as to achieve a miniaturization of the electric field sensor, the magnetic field sensor, and the detector as a whole, and a point-by-point probing as well. The operation frequencies of the detector are set to be 1 Hz and 0.2 Hz, and natural signals are received on the ground with clear, easily identifiable output waveforms. This paper introduces the basic principle of applying group delay difference to measure the conductivity variations of deep layer, the structure of the group delay difference detector, the natural signal waveform received on the ground, and the recognition method of useful message. Also the paper discussed the problem of whether electromagnetic waves in the deep layer with frequency less than or equal to 1 Hz are able to arrive at the ground and to be received.
文章引用: 王友善 , 王绍阳 (2015) 用电磁波群时延差的异常变化预测短临地震的基本原理与探测仪器。 地球科学前沿， 5， 314-322. doi: 10.12677/AG.2015.54032
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