THE ASSESSMNET OF SEISMIC HAZARD AND GSHAP ASPECTS

Objectives of earthquake hazard assessment The objective of an earthquake hazard analysis is to evaluate the probability of exceeding a particular level of ground motion (such as a certain value of peak acceleration) at a site during a specified lime interval (such as ۱۰۰ years).Limits of earthquake hazard assessment Seismic hazard assessment in low seismicity areas is much more subject to large errors than in areas with high earthquake activity. This is specially the case if the time span of the available data catalogue is considerably smaller than the mean return period of large events, for which the hazard is to be calculated.Incorporation of uncertainties Uncertainties are introduced by lack of data or lack of knowledge. In seismic hazard computations the uncertainties of the basic input data must be taken into account in proper form (McGuire ۱۹۹۳). This task is accomplished by making alternative interpretations where significant uncertainties are existing and applies especially for: ۱. the size, location and time of occurrence of future earthquakes, ۲. the attenuation of seismic waves as they propagate from all possible seismic sources in the region to all possib.c sites.