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Abstract: We conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for Turkey and the adjacent areas, applying the maximum likelihood method. The procedure allows for the use of either historical or instrumental data, or even a combination of the two. By using this method, we can estimate the earthquake hazard parameters, which include the maximum regional magnitude Mˆ max, the activity rate of seismic events and the well-known bˆ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. These three parameters are determined simultaneously using an iterative scheme. The uncertainty in the determination of the magnitudes was also taken into consideration. The return periods (RP) of earthquakes with a magnitude M≥m are also evaluated. The whole examined area is divided into 24 seismic regions based on their seismotectonic regime. The homogeneity of the magnitudes is an essential factor in such studies. In order to achieve homogeneity of the magnitudes, formulas that convert any magnitude to an M S -surface scale are developed. New completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions. Each of the obtained parameters is distributed into its respective seismic region, allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map. The earthquake hazard level is also calculated as a function of the form Θ =(Mˆ max,RP 6.0), and a relative hazard scale (defined as the index K) is defined for each seismic region. The investigated regions are then classified into five groups using these parameters. This classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity. An attempt is then made to relate these values to the local tectonics. [Copyright &y& Elsevier]

Because the instrumental records of Turkey are far from being satisfactory for modeling the seismic hazard using the probabilistic approach, an attempt was made in this study to accomplish it through the deterministic way. In this regard, all active faults of Turkey, small and large, were evaluated together to obtain major fault systems. Then, the procedure suggested by Wells and Coppersmith [Bull. Seismol. Soc. Am. 4 (1994) 975] applied to those faults to obtain the maximum magnitude earthquake that they can generate. To do this, it was assumed that 1/3 of the total fault length would rupture to yield the maximum earthquake. Following that, seven different attenuation relationships of the strong ground motion were utilized to calculate the maximum horizontal ground accelerations for the whole Turkey at 0.2° intervals using the computer model TUMDES written in BASIC programming language.The computed peak ground acceleration (pga) values were contoured and the iso-acceleration map based on Sadigh et al. [Seismol. Res. Lett. 1 (1997) 180] relationship was selected as the new seismic hazard map of Turkey on which the seismic zonations were determined as following: pga>0.3 g Zone 1; 0.3 g

Recent developments in the neotectonic framework of Turkey introduced new tectonic elements necessitating the reconstruction of Turkey''s seismic hazard map. In this regard, 14 seismic source zones were delineated. Maximum earthquake magnitudes for each seismic zones were determined using the fault rupture length approximation. Regression coefficients of the earthquake magnitude–frequency relationships for the seismic zones were compiled mostly from earlier works. Along with these data, a strong ground motion attenuation relationship developed by Joyner and Boore [Joyner, W.B., Boore, D.M., 1988. Measurement, characterization, and prediction of strong ground motion. Earthquake Engineering and Soil Dynamics, 2. Recent Advances Ground Motion Evaluation, pp. 43–102.] was utilized to model the seismic hazard for Turkey using the probabilistic approach. For the modeling, the “earthquake location uncertainty” concept was employed. A grid of 5106 points with 0.2° intervals was constituted for the area encompassed by the 25–46°E longitudes and 35–43°N latitudes. For the return periods of 100 and 475 years, the peak horizontal ground acceleration (pga) in bedrock was computed for each grid point. Isoacceleration maps for the return periods of 100 and 475 years were constructed by contouring the pga values at each node. [Copyright &y& Elsevier]