Analysis of magnitude for earthquake detection using primary waves and secondary waves

摘要

Earthquake is a natural calamity, also known as quake or tremor, occurs due to release of sudden energy which is stored under stress field in the earth's crust. The stored energy is released due to imbalance in stress filed which creates three events called foreshock, main shock and aftershock. Each event is associated with some waves such as primary waves, secondary waves, Rayleigh waves, Stoneley waves and Love waves. As these waves travels from interior of earth to surface they degrades in magnitude and intensity, only a part of the original waves reach the earth surface originated in earth's crust which are recorded as seismograph. Till to date, many of the researchers applied different techniques like prediction based on radon emissions, prediction using extraction of instantaneous frequency from underground water. As the earthquake occurs due to transmission of waves, hence feature extraction from the seismic signal is the efficient approach to predict the earthquake. The parameters of seismic signal are analyzed by using fast fourier transform spectrum analysis. The magnitude which forms the base of analysis is used for the detection of earthquake. The minor quakes are neglected and the surface wave magnitude of the quakes that show impact on earth's surface is calculated and found it as 4.0. Hence, the occurrence of earthquake can be predicted if the magnitude exceeds 4.0.