Abstract

It is necessary to prepare the microzonation maps and determine the better soil sites in settlement areas which are located on active tectonic regions. In this study, the geological, geophysical and geotechnical conditions of the Esenler district (Istanbul) were investigated and a small scales microzonation study was carried out. The northern sides of the study area generally represented by Lower Carboniferous aged graywacke (sandstone) and some areas in the southern parts represented by Upper Miocene aged limestone. The soil units consist of high plastic, hard-solid consistency and overconsolidated thick clay layers. The earthquake hazard of the study area is determined by using deterministic and probabilistic approaches. The probabilistic hazard analysis indicated that the occurrence probability of a 7 magnitude (M_w=7) earthquake is 7.42% in 10 years and 32% in 50 years (Poisson probability dispersion).  The deterministic earthquake hazard analysis is also performed for Adalar Fault in Marmara Sea and accelerations were estimated for study area by several attenuation relations. Soil amplification factors and site characteristic periods were determined and estimated by seismic measurements. Shear wave velocity (V_s30) values, soil amplification values and site characteristic periods are changing between 257 to 1255 m/s, 1 to 2.4 and 0.46 to 0.1 s in the study area, respectively.

Key words: Microzonation, seismic hazard, soil amplification, soil condition.