From national to local governments and private sectors, many organizations have carried out earthquakes damage estimation of their facilities by comparing their strength and earthquake demand. Based on these estimations, they have established plans for disaster reduction measures. Although these earthquake damage estimations are conducted by consuming large budgets and time, in many cases the results are neither used well nor trusted, especially by specialists. Why?
The major reason is that these estimation results are calculated based upon chains of assumptions. In other words, the probability of having the assumptions adopted in the damage estimation calculation is very low. Furthermore, simulations are carried out under static conditions while real phenomenon is very dynamic.
Although a static condition is used in many simulations, the time factor is certainly very important, especially for human related activities. For a reliable assessment of earthquake disaster damage, three time factors must be considered. The first defines the characteristics of the social system and development level of the affected area. The second is related to the point in time when the event occurs : season, month, day, hour, etc. The last is time elapsed after the event.
Recently, accurate estimations of the characteristics of an earthquake (location, magnitude, mechanism, etc.) and the strong ground motion at each site is improving. However, even if accuracy becomes reliable, damage caused by the event cannot be discussed quantitatively as there is great uncertainty due to time factors and research on how to manage this uncertainty is scarce.
In this paper, the direction of future research on earthquake damage evaluation and disaster countermeasure plans are discussed stressing the above-mentioned issues. Some studies on these matters are introduced.
