Strong ground motion attenuation relationship model for Marmara region

Key Words: earthquake, strong-motion, attenuation relationship, seismic hazard, strong motion network, accelerography, shear wave velocity, peak acceleration, multiple regression. The aim of this study is to develop a new and up-to-date attenuation relationship for Marmara region as a function of distance, magnitude and local site conditions. Therefore, earthquake activity in the rectangular region bounded by 40-42 North latitudes and 26-32 East longitudes are examined with strong motion records from 1983 to the present time. 721 acceleration records taken from 128 earthquakes with magnitudes equal or greater than 4.0 are taken into consideration with other earthquake parameters. Acceleration records taken from accelerometers which were installed at 87 different locations in Marmara region are used in this study. Local soil conditions are categorized according to average shear-wave velocity within 30 m depth. Together with other earthquakes occurred in this region, main shock and aftershock records taken from two destructive earthquakes occurred in 1999 are used in model studies for the region. Great number of records obtained for the first time in our country form a powerful data base. Statistical methods are applied to obtain attenuation relationship model by using data set that is prepared. Therefore, a number of mathematical models are applied to obtain best statistical fit to peak ground acceleration and 5 % damped elastic spectral accelerations as a function of earthquake magnitude, distance and local site conditions. As a result, a up-to-date ground acceleration attenuation model is developed for Marmara region by using multiple regression method.