Earthquake investigation near the fault using simulated acceleration mapping and design spectrum

The locations of large cities in Iran in areas close to the faults and the activities of many of these faults have caused attention to the seismic characteristics of the areas near the faults. Meanwhile, the unavailability of near-fault field maps in these areas, and also, the weakness of design regulations in providing design spectra appropriate to the near-fault areas, lead to a detailed study and parameterization of earthquakes near the faults. The parameters of maximum horizontal velocity and pulse frequency are very important in parameterizing near-fault earthquakes and producing simulation maps. Moreover, design spectra provided for areas close to faults can be used in the design of many structures near active faults. In this study, with the help of AIC information criterion, nonlinear regression analysis and by considering the errors within and between events on a set of near-fault field maps, equations for predicting pulse periodicity and maximum horizontal velocity have been obtained. The resulting pulse model and the low frequency section of the mapping are generated. To produce a simulated acceleration, the high frequency portion of the mapping must be combined with the low frequency portion. Thus, after producing the high frequency section and its combination with the low frequency portion, the simulated acceleration map is generated. Furthermore, with the help of a set of near-fault maps and extraction of parameters related to each map, the spectrum with the characteristics of the near-fault area has been presented. The results of this study show that the produced acceleration in this study has a very high accuracy. In addition, the spectrum presented in this study can eliminate the weakness of the spectrum of regulations for the areas close to the faults. In this study, to investigate the accuracy of the results and the reduction relations, two maps of Chi Chi and Bam earthquakes have been produced. These two maps are related to two different fault mechanisms. One of the objectives of studying the earthquakes near the faults is to prepare the design spectrum for its direct use in the seismic design of structures. In this research, using a data set including information on rock and soil structures, the design spectrum and its parameters with the seismic characteristics of the areas near the faults are prepared.