REALISTIC GROUND MOTION AT TEHRAN: A CASE STUDY THE 2004 FIROZABAD KOJOOR EARTHQUAKE, NORTH OF TEHRAN, IRAN

The computation of complete synthetic seismograms has been used to simulate observed strong ground motions recorded at Tehran during the 2004 Firozabd Kojoor earthquake, which occurred 60 km north of the town. The bedrock model is defined as a stack of horizontal layers, each characterized by its thickness, longitudinal and transversal wave velocity, density, and Q-factor, controlling the anelastiic attenuation. The seismograms were computed, for frequencies reaching 10 Hz and subsequently filtered to f =6 Hz, along a north-south profile 14 km long. These signals are numerically propagated through the laterally varying local structure by the finite-difference scheme. The comparison between observed and simulated time histories indicates a quite good agreement between observed and simulated time histories and response spectra. The results of the modeling shows that the methodology can be easily used for seismic zoning and microzoning in Tehran.