Intensity attenuation formulas are proposed for strong earthquakes of modified Mercalli intensity (MMI) VIII-X in the Sino-Korean craton. Isoseismals of 11 earthquakes that occurred in the craton during the twentieth century are used in the analysis. New attenuation formulas are expressed as mula" id="disp-formula-1">mg class="math tex" alt="Formula" src="783/embed/tex-math-1.gif" /> where m>Im>0 and m>Im> are the epicentral intensity and intensity at an epicentral distance m>D;m> φ0 and φ are constants having some geometrical implications of the attenuation pattern; and m>Dm>0 is the reference value for the isoseismal m>Im>0. Constants φ0 and φ have values of 1.31 and 1.77, respectively. Values of m>Dm>0 for m>Im>0 = X, IX, and VIII are 9.3, 6.5, and 5.2, respectively. New attenuation relations fit the observations better than the conventional relations such as mula" id="disp-formula-2">mg class="math tex" alt="Formula" src="783/embed/tex-math-2.gif" /> mula" id="disp-formula-3">mg class="math tex" alt="Formula" src="783/embed/tex-math-3.gif" /> It appears that the new formulas represent intensity attenuation of Korean earthquakes well to the limits of felt areas. New attenuation formulas using the relation between the total felt area and m>Im>0 may be used in the estimation of epicentral intensities of strong Korean historical earthquakes for which only felt places are provided in documents without information on earthquake damages or phenomena. The formulas may also be used in more realistic evaluation of the seismic hazard of the Korean peninsula.
