Abstract: The electromagnetic radiation instrument “EMAOS” was developed in the period of “Ninth-five Years” Plan. The instrument “EMAOS” is improved from the theory of the telluric electromagnetic sounding. The received spectrum band of the instrument extends from 0.01 Hz to 10 Hz; hence the sounding depth is between 0 and 20 km where shallow earthquakes occur. The recorded electromagnetic disturbance is the electromagnetic field form the electrokinetic effect under action of the stress field. It improves the reliability of the recorded information because the electric and the magnetic field are recorded at same time. The records show that the feature of anomaly before earthquakes is almost consistent with the result of the analog record. Therefore, we can apply the prediction index of analog records in the digital record research.

Key words: Electromagnetic radiation, Observation principle, Telluric electromagnetic sounding, Sounding depth, Electrokinetic effect