TIME AND SPACE SCANNING OF THE b-VALUE——A METHOD FOR MONITORING THE DEVELOPMENT OF CATASTROPHIC EARTHQUAKES

Statistical analysis of the b-value in the frequency-magnitude relation N = exp(A - bM) was performed for several years before the Tangshan Earthquake on July 28, 1976 (Ms = 7.8) and before some other catastrophic earthquakes. It was shown that objective and statistically significant b-values could be always obtained provided seismic data being treated correctly and statistical methods being used properly. On the basis of a phenomenological discussion of the frequency-magnitude relation in the view of Mogi[1]and Scholz[2], it was concluded that fr-value is not only a parameter in statistical analysis, but also has its own physical meaning. It reflects the average stress being applied to the region considered and the extent of approach to its strength limits. Therefore, dynamical scanning of b-values in time and space goes beyond the scope of simple statistical prediction and becomes a method to monitor the concentration and migration process of stress and to monitor the development of catastrophic earthquakes.A direct procedure for non-linear least-squere fitting to the exponential frequency-magnitude distribution was suggested in this work. This is an effective method for estimation which does give more exact limits for statistical errors.