Spatial variation model of seismic ground motion for Istanbul

Abstract

Earthquake induced base motions of elongated structures will not be uniform. This variation of ground motion has a nonnegligible effect on the dynamic response of lifelines that has led to investigations of characterization and modelling of the spatially varying earthquake ground motion within the last decade. In this context, spatial variation of seismic ground motion in Istanbul is analyzed. After the introduction of the concept of coherency function and its conventional estimation procedure, estimation of coherency from recorded data and its interpretation are presented. The lagged coherency is calculated by the conventional coherency estimation scheme applied to six earthquakes registered by the Istanbul Earthquake Rapid Response System. A coherency model for Istanbul is derived that will enable to simulate spatially variable ground motion needed as input in the design of extended structures. Simulation of ground motion at pairs of closely spaced locations is presented that consider the derived coherencies in their scheme. The results are compared with actual recordings from the same locations. Simulation of spatially variable ground motion consistent with a coherency function is stated.