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High-pass filtering that is one of the most efficient methods in removing long-period noise of accelerograms is investigated for its effect on nonlinear oscillator deformation response. Within this context, uncertainty in filter cut-off periods that would significantly modify the low-frequency content of accelerograms come into prominence for obtaining reliable long-period displacement response. Analog and digital ground-motion records from recently compiled Turkish strong-motion database are used and these records are high-pass filtered with a consistent methodology by randomly generated filter cut-offs that represent different filter cut-off decisions of the analysts. The uncertainty in inelastic spectral and residual displacements (SDIE and SDR, respectively) due to variations in filter cut-offs is examined to derive the usable period ranges where the effect of high-pass filtering is tolerable. Non-degrading, stiffness degrading and stiffness and strength degrading oscillator behavior are considered in these analyses. The level of nonlinear behavior in single degree of freedom (SDOF) response is described by varying the yield strength (R, normalized yield strength) and displacement ductility (&micro / ) levels. The usable period ranges that depend on magnitude, recording quality, level of inelasticity and level of degradation are determined for SDIE through robust probabilistic methodologies.

The primary objective of this study is to evaluate the seismic hazard in the Eastern Marmara Region using improved seismic source models and enhanced ground motion prediction models by probabilistic approach. Geometry of the fault zones (length, width, dip angle, segmentation points etc.) is determined by the help of available fault maps and traced source lines on the satellite images. State of the art rupture model proposed by USGS Working Group in 2002 is applied to the source system. Composite reoccurrence model is used for all seismic sources in the region to represent the characteristic behavior of North Anatolian Fault. New and improved global ground motion models (NGA models) are used to model the ground motion variability for this study. Previous studies, in general, used regional models or older ground motion prediction models which were updated by their developers during the NGA project. New NGA models were improved in terms of additional prediction parameters (such as depth of the source, basin effects, site dependent standard deviations, etc.), statistical approach, and very well constrained global database. The use of NGA models reduced the epistemic uncertainty in the total hazard incorporated by regional or older models using smaller datasets. The results of the study is presented in terms of hazard curves, deaggregation of the hazard and uniform hazard spectrum for six main locations in the region (Adapazari, Duzce, Golcuk, Izmit, Iznik, and Sapanca City Centers) to provide basis for seismic design of special structures in the area. Hazard maps of the region for rock site conditions at the accepted levels of risk by Turkish Earthquake Code (TEC-2007) are provided to allow the user perform site-specific hazard assessment for local site conditions and develop site-specific design spectrum. Comparison of TEC-2007 design spectrum with the uniform hazard spectrum developed for selected locations is also presented for future reference.