பூமி அறிவியல் & காலநிலை மாற்றம் இதழ்

சுருக்கம்

A High Resolution Measurement of Foreshocks for the Prediction of Earthquakes

S. Javed Arif, M. S. Jamil Asghar and K. Farahim Khan

It has been recently reported that there is a very strong relationship and well defined similarities in the vibration pattern of foreshocks, main shock and aftershocks which can be used for the prediction of earthquake. It has also been established that foreshocks are the best accredited forecaster of earthquakes. However, the foreshocks consist of an adverse combination of extremely high contents of velocity and acceleration superimposed over a very low frequency wave. Therefore, the existing low resolution accelerometers and seismometers are incapable to get an insight of the signatures of these foreshocks. In the proposed method, a fast rotating magnetic field (RMF) is used to measure the velocity and acceleration of vibrations at high resolution and accuracy. To simulate the foreshocks, a microprocessor based rocking vibration arrangement is used which generates vibrations similar to the foreshocks. These vibrations are mechanically transmitted to the rotor of a synchro. According to the movement of the rotor of synchro, the RMF generates voltage signals at the rotor output and thereby a broad spectrum of square pulses is produced with the help of a logic circuit. Consequently, all possible values of instantaneous velocity and acceleration of foreshocks are obtained, in terms of pulse widths. Hence, it gives a deep insight to recognize the distinct features of signature of foreshocks. This would help in an accurate prediction of earthquakes. The measurement is also simultaneously communicated to a PC for monitoring and remote sensing. The proposed system is simply coupled with the conventional standard spring attachment system to measure the actual foreshocks. A number of such units may be placed at different earthquake prone areas for centralized monitoring.