Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

3 14 De-yi Feng, Ming-zhou Lin, and Kun-yuan Zhunngfor the Donmirig and Diritau regions together. Their iioriiialized forms are&I = (0.139 0.139 0.147 0.174 0.263 0.139), andQ2 = (0.146 0.146 0.147 0.157 0.259 0.146).From the corriporierits of matrices-vectors QI arid Q2, we may coiiclude that tlieintensity of the Hozliei earthquake is equal to VII+ in tlie Hozliei region, and VIIin the Doiiniing and Dintau regions. For comparison, Figure 1 shows tlie isoseisiiialcurves obtained from conventional assessment, and the dashed isoseisinal line bytlie fuzzy sets method.(2) Intensity of the 1920 Raiyuan (A! = 8.5) Earthquake. By use of the Iiistoricaldata about tlie disaster of the Haiyuari earthquake (Seismological Institute ofLanzliou and Seismological Bureau of Ningxia Region, 1980) we may take approximatelythe average width of tlie earth fissure in the Haiyuari region as: a = 250 cm,b = 0 for rock fissure; arid a = 550 ciii, b = 0 for grouiicl fissure. By using Table 2,we obtain the degree riiatrix of approaching as:= (0.735 0.826 0.5 0*5) ’where the rows correspond to rock fissure and ground fissure, arid the columnscorrespond to intensity XI1 and intensity XI. Its normalized form isQ = (::::i:::) .D:heVIIo Dintau15 kmFigure 1. Intensity of Hozhei Earthquake. The dnshed line denotes a corrected isoseisnialline.