1920年海原8.5级地震对兰州地区的减震作用

REDUCIBLE SEISMIC INTENSITY IN THE LANZHOU AREA DUE TO THE 1920 HAIYUAN M8.5 EARTHQUAKE

１９２０年海原８．５级大震在其发震断层两侧１６０ｋｍ范围内今后几百年内不会发生大于６．５级的地震．兰州地区距海原大震断层约１２０ｋｍ，所以兰州地区今后几百年内也不会发生大于６．５级的地震，即不会发生烈度大于Ⅷ度的地震．而兰州地区是按Ⅷ度抗震设防的，即使今后发生６．５级的地震，其破坏亦不会很严重．这是按最坏情况考虑的．

Effective distance to reduce seismic intensity on two sides of the main fault causing the 1920 Haiyuan M8.5 earthquake is about 160 km.Within the distance no M>6.5 earthquake will occur during the future several hundreds of years.Because Lanzhou City is 120 km away from the main fault, in the city no M>6.5 earthquake will occur in a few hundreds of years.Structures and buildings in Lanzhou City were designed according to antiseismic standard of Ⅷ degree on the intensity scale.Even though a M6.5 earthquake will occur in future,its destruction would not be too heavy.It is a consideration in the worst case.