DETERMINATION OF MAGNITUDE OF NEAR EARTHQUAKES BY MEANS OF PERSISTING TIME OF SEISMIC WAVES IN THE SICHUAN-YUNNAN REGION

In this work, we have used a large amount of recorded earthquake data of the Sichuan-Yunnan region for discussing attenuation of coda waves of near earthquakes with time, the static magnification of the VGK seismographs and the relation between the persisting times of earthquake waves and the epicentral distances. We obtain the following two formulas for determining the near earthquake magnitudes in the Sichuan-Yunnan region, using persisting times of vertical and horizontal component waves:MDZ=0.94+1.57log(tDUV)+0.00136△(1)MDM=0.78+1.60log(tDUM)+0.00114△(2) The results show that the standard error of near earthquake magnitudes derived from, the persisting time tDUV is less than that from amplitudes which illustrate that this method is perhaps better for determining near earthquake magnitudes.