REGIONALIZATION OF ATTENUATION OF SEISMIC INTENSITY IN CHINA

In this paper, isoseismal maps of 198 Chinese earthquakes occurring between 1900 and 1980 were used in calculating the rate of attenuation of seismic intensity with distance by using the equation lnIi/I0=a-blnRi-cRi where I0 is the epioentral intensity, I1 is the equivalent radius of the area surrounded by the isoseismal of intensity A. As a result, China was divided into 12 regions. For regions in which the form of the isoseismals is apparently influenced by the tectonic background, attenuation of intensity along the major and the minor axes of the ellipses of seismals were calculated separately. For the near field, a depth-factor, D, was added, and the following equation was obtained lnIi/I0=a-bln(Ri+D)-cRi The results of regionalization and the effect of the different factors in the two equations were discussed.