Generation of a family of artificial earthquakes from a set of records of an actual earthquake

To properly evaluate the response of three-dimensional structures it is required to consider the effect of both components of earthquake ground motions (bidirectional seismic excitation). Given that a limited number of records of real earthquakes of the level required by the Chilean seismic code exist, artificial records are generated that are similar to the real ones, in terms of two simultaneous horizontal components. To develop the artificial earthquakes, the records obtained from strong-motion accelerographs during the earthquake of March 3, 1985 were considered (10 sites). The characteristics of the accelerations records are described and quantified using the concepts of Arias' Intensity, Coefficient of Correlation (over the duration of the record), Evolution in time of the Correlation (10 seconds moving window), the envelopes of the correlations in time, and the average of their maximum values. For the two horizontal components of the records, the response spectra (pseudo-accelerations) were obtained (elastic response, 5% damping ratio) after the principal components were scaled to a peak acceleration of 0.4g. Using the average of the pseudo-acceleration response spectrum of each of the horizontal components, a family of artificial earthquake records that match (within 5%) the ordinates of the average spectra was generated using a well-known procedure. Only those records whose instantaneous correlation are within the envelopes as obtained in the characterization of the real earthquakes and which have characteristics similar to those of the real records in terms of the other properties used in the characterization are considered acceptable.