Strong motion simulation by empirical green's function method for Bursa Armutlu peninsula

Abstract

According to results of time dependent probabilistic hazard assessments, The fault segment extending between Gemlik-Bandirma and segment passing through the southern part of Iznik Lake have potentials of producing a magnitude 7.2+ event with 1000 year recurrence time and second highest hazard rate in Marmara Region. For future risk mitigation strategies, it necessitates preparing scenario earthquakes. Near-field generation of scenario events from mentioned fault segments was performed at nine BYTNET stations. Horizontal components of records with frequency range of 0.5-10 Hertz were used. Simulations were performed by using Empirical Green’s Function Method which essentially uses small events as Green’s function and sums them up to follow the omega-squared scaling law. Gemlik Earthquake was utilized as Green’s Function throughout analysis. As an initial calculation focal mechanism of Gemlik Earthquake was confirmed by simulating it with Mw= 3.3 event. For scenario case, assumption is that scenarios occur at the same location of Mw= 4.8 event with same focal mechanism. A single asperity model was adopted. Size of asperities was determined according to stress drop ratio equality between target and element event. Scenarios were defined by changing rupture initiation points. Near field effects at each scenario simulation were investigated via observing components perpendicular and parallel to fault plane. Various empirical attenuation relationships were compared with simulated peak ground accelerations and velocities. Simulated acceleration spectra pertaining to fault parallel and normal components were compared with Turkish Seismic Design Code. Finally, It was observed whether peak values were in harmony with attenuation curves or not.