It has been shown that during the 1999 August 17 Izmit earthquake local site effects affected ground motion in distant areas such as the damage observed in Avcilar, west of. Istanbul. Despite efforts to study soil conditions in Istanbul in recent years, site effect problems in the deeper soil are not completely defined. Besides this, the main problems expected in the city of. Istanbul will be the result of amplification of ground motion due to an earthquake. To understand these effects, studies were carried out which showed either limited measurements or provided data for shallow depth by obtaining only the depth of engineering bedrock or the average shear wave velocity down to 30 m depth (V-s30).