Probabilistic Method to Estimate Design Accelerograms in Seville and Granada Based on Uniform Seismic Hazard Response Spectra

The response of a structure affected by an earthquake is the result of “filtering” the seismic signal through the structure. A dynamic analysis of a structure requires the previous definition of the accelerogram and the structure characteristics. A complete calculation implies working out the seismic response in all points of the structure; that is, calculating the seismic response in an infinite number of points and in an infinite number of instants. (Meirovitch, 1985) has demonstrated that, with an infinite number of points and instants, the problem has no numerical solution. To solve the numerical problem, models with a finite number of predeterminated points are defined. The response of a structure subject to a seismic movement can be determined by two methods: either using the accelerograms recorded near the site, or using visco-elastic response spectra. The first method can only be used in places where many accelerograms have been recorded, and needs a probabilistic calculation to ascertain the design accelerograms. This procedure can be used for linear and non-linear analyses. In both cases various records of a frequency similar to that expected at the location of the structure, may be used to obtain realistic calculation results. A structural analysis for all the accelerograms considered must be carried out in order to obtain a calculation envelope or carry out the probabilistic study. This procedure implies a significant work. This procedure has the difficulty of finding accelerograms at the location of the structure. In some regions, with a vast history of large earthquakes, such as Japan and California, a wide network of recording stations is available and provides many records for large earthquakes, for different type of soils and for a wide range of distances. In regions of minor seismicity, the network of recording stations is not so wide, or is not old enough, so that the number of records is insufficient. For the analysis of minor seismic activity regions, records from other regions are used, or artificial accelerograms are generated. Artificial accelerograms have the advantage that, from a minimum number of parameters, accelerograms can be obtained.