1 STRONG GROUND MOTION SIMULATION OF THE 1972 MANAGUA, NICARAGUA EARTHQUAKE BASED ON EMPIRICAL GREEN’S FUNCTION METHOD Edwin Nadir Castrillo Osorio ∗ Supervisor: Toshiaki Yokoi**, MEE06007 Nobuo Hurukawa ** ABSTRACT We simulated the strong motion record obtained at the Esso Refinery station from the 1972 Managua, Nicaragua earthquake using its aftershock record through the empirical Green’s function method. In order to obtain the best initial guess for the modeling, we carried out the hypocenter relocation through the modified joint hypocenter determination method using the phase data listed in the ISC seismic catalog. Finally, we found out that the source model which best fitted to the observed waveform had two asperities. This asperity model fell on the trend of the empirical relation between the seismic moment and the strong motion generation area. Keywords: Empirical Green’s function, asperity, heterogeneous source model. INTRODUCTION One of the very useful outcome of the empirical Green’s function method (EGFM) is that it provides the strong motion generator area, and this is almost equivalent to that of asperities which generates the earthquakes (Miyake et al. 2000), where asperities are defined as the areas with the highest stress drop. The location of the earthquake is very important in order to modelize in the best way possible. For this purpose, the modified joint hypocenter determination was used. This method allows correcting many hypocenter locations simultaneously taking into account station correction and a difference in trade off, and this is useful to reduce error in the location. The main purpose of this study is to simulate the 1972 Managua earthquake. Simulation here should be understood as taking a time history best fit to that of a specified earthquake. This will be done by using the information of the National seismic network. RELOCATION OF THE HYPOCENTER Exact location facilitates the modeling of the fault parameters concerning the EGF method, because the more exact the location is, the better fit between the synthetic and the observed seismogram. Here the analysis and method to obtain the relocation through the modified joint hypocenter determination is skipped. We are interested just present the results obtained in general way. ∗ Research Geoscientific Center, National Autonomous University of Nicaragua (CIGEO- UNAN/Managua) ** International Institute of Seismology and Earthquake Engineering (IISEE), BRI, Japan