Study of the intensity attenuation law in the East China Plain and the northwest of China

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Study of the intensity attenuation law in the East China Plain and the northwest of China

In order to obtain the intensity attenuation law in the north of China, the studied region is divided into four regions according to topographical and geological feature.For making the shape of isoseismal lines from ellipse to circle with the increase of distance,the tail-limited method is derived.Using the ellipse-projection,two-step regression,head-limited and tail-limited method,their intensity attenuation laws are obtained.Through the study of the intensity attenuation law in the greater part of China,the author considers that the intensity attenuation law of China can be roughly divided into:plain-type and mountain-type.So the intensity attenuation law in East China Plain(plain-type for short) can be used in plains and deposit areas and that of the greater part of the regions in Yunnan and Sichuan Provinces(mountain-type for short) can be used in mountains.For the earthquakes occurred on the borders,their attenuation laws are classified respectively.In the side of mountains belong to mountain-type,and in the side of plain plain-type.In the areas where two kinds of topograph intersect isoseismal lines are irregular and the attenuation laws are more complex.