COMPOSITION OF SEISMIC LOAD BASED ON THE ALLOWABLE LEVEL OF EARTHQUAKE DAMAGE

在地震灾害预防中，最重要的是将地震灾害减少到最小程度，不产生严重的社会影响。社会影响可以通过报纸对地震灾害的报道量来衡量。对1946 ~ 1995年地震发生后30天报纸的震害报道占总报道的比例进行了调查。报告率随震后天数的增加而降低，可用指数函数近似。利用该关系式可以估算地震灾害的最小程度，而要估算地震灾害的允许程度，必须给出日本的可靠地震危险性。本文用基本上由地震构造确定的震源区，用概率方法分析了日本的地震危险性图。地震发生参数是由地震目录的修正震级分布确定的。利用这些参数计算了最大加速度和速度的极值分布。根据100年一遇加速度的地震危险图，东日本地区的数值约为300 gals，其他地区的数值在100 ~ 200 gals之间。为了防止社会恐慌，必须将房屋的地震破坏总数降低到社会允许的水平以下。房屋的破坏量受破坏概率的控制，破坏概率与房屋集中度成反比。提出了一种结构地震荷载的城市地震因子，使房屋的总破坏为常数。使用一个简单的单自由度结构的因素进行检查。该系数增加了100%的地区的18倍至16倍的浓度的房屋。

The most important thing in the prevention of earthquake disaster is to reduce the seismic damage to the slightest level which does not yield severe social impact. The social impact can be estimated by the amount of report about seismic damage in the newspaper. The report ratio of seismic damage report to total report in newspapers is surveyed for 30 days after earthquakes from 1946 to 1995. The report ratio decreases with day after earthquake and it can be approximatee by the exponential function. The slightest level of earthquake disaster is estimated using this relation.Reliabale seismic hazard of Japan must be given to estimate seismic damage to be the allowable level of damage. Seismic hazard maps in Japan are analyzed the probabilistic method using the area1, souces which are determined basically from the seismotectonics. Seismic occurrence parameters are determined from the modified magitude ditributions of the earthquake catalogs. The extreme value distributions of the maximum acceleration and the velocity are calculated using these parameters. The seismic hazard map of the 100-year return period of acceleration shows that values in east Japan are almost 300 gals and values in the other region are from 100 to 200 gals.The total number of seismic damage of houses must be decreased below some social allowable level to prevent the social panic. The amount of damage of houses is controlled by the probability of failure which is reciprocal of the concentration of houses. A seismic urban factor of the seismic load of structure is proposed to yield the constant total damage of houses. The factor is examined using a simple single degree of freedom structure. The factor increases by 100% for the region of eighteen times to sixteen times concentrations of houses.