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Collision of the Arabian and African plates with Eurasia forces the Anatolian micro-plate to move west-ward. In the Aegean Sea, the Anatolian micro-plate rotates counter-clockwise and extends due to the subduction zone along the Hellenic Arc. This deformation results in faulting activity along the western coast of Turkey, which is capable of producing destructive earthquakes. Izmir, the third largest city in Turkey and the largest along the western coast, has been destroyed by large earthquakes several times in recent history, latest in 1778. In a previous ground motion simulation study it was shown that the Izmir fault (normal) which lies under the city and the Tuzla fault (strike-slip) southwest of the city pose the largest threat to Izmir, when compared to ruptures on other faults in the vicinity of the city. In this study, a new deterministic seismic hazard analysis is conducted based on a refined slip model, using information from previous ruptures as the Borah Peak, Idaho (normal) and Kobe, Japan (strike-slip) events.
The method adopted is a hybrid broadband frequency ground motion simulation technique, which has previously been validated. The earthquake scenarios are based on existing knowledge about source parameters, local as well as regional. The earthquake rupture scenarios on the faults are found to produce peak ground acceleration values in the centre of Izmir of up to 335 cm/s2 and 225 cm/s2, on bedrock level, for Izmir and Tuzla faults respectively. Considering the site effect potential in the area, these values need to be treated as lower thresholds. The distribution of peak ground motion is found to be highly dependent on the input parameters for the ground motion simulations. Sensitivity of the ground motion to input parameters is therefore investigated by changing single parameters in the input model like the average stress drop, rise time and the rupture velocity as well as a change in the hypocenter location in order to study the effect of rupture directivity on the simulated seismic waves.
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