Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Site Safety Evaluation In The Region Between Istanbul Buyukcekmece – Kucukcekmece Lakes

17 August Izmit (Gölcük) and 12 November Düzce earthquakes happened in 1999, brought out that there can be a big earthquake in Istanbul, which is the most important metropol of Turkey. As a result of a big earthquake in Istanbul, this will effect the whole country because of the economical and social damages besides the loss of life and the goods. Throughout the 2000 years of Istanbul’s history, there were minimum 14 earthquakes with maximum intensities over IX. When we look at the history of the earthquakes, Istanbul is exposed to an earthquake approximately every 100 years. Although Avcılar is 100 km. far away from Gölcük earthquake center, it was the most affected town in the 17 August 1999 Gölcük earthquake.

After the 17 August 1999 Gölcük earthquake, determination of the soil dynamic properties between Büyükçekmece and Küçükçekmece lakes become very important in geology. To examine this place, it’s necessary that maps that show selection of areas for construction and more important than that, maps geared towards the aims of projections of stability in earthquakes for local soil dynamic properties and their probable behaviour during the earthquakes should be prepared.

The most important thing in the aim of works of land-use is; the determination of the soil amplification properties of the place between Büyükçekmece and Küçükçekmece lakes faced with Quarternary, Upper Miocene and Oligocene units. Liquefaction and slope stability are the other important methods in works of land-use. As a majority of current structuring in the place between the Büyükçekmece and Küçükçekmece lakes in on the plain area and on minor-slope areas, soil amplification has been taken into consideration evaluating appropriateness for properness of localization. In accordance with this, liquefaction in alluvial areas and in areas where there is more than %5 slope considering localization evaluation without stability analysis displays risks.

In the content of this thesis, the soil amplification between Büyükçekmece and Küçükçekmece lakes are evaluated using the number of blows obtained from Standard Penetration Tests (SPT-N), seismic and microtremor datas which were gained by the works which were made in the areas of Avcılar, Esenyurt, Yakuplu, Beylikdüzü (Kavaklı), Kıraç, Gürpınar and Büyükçekmece municipalitys. The shear wave velocities (V_S30) from the number of blows obtained from Standard Penetration Tests (SPT-N) of boreholes are compared with Imai (1978), İyisan (1994), Lee(1990) and Ohta and Goto (1978) emphirical and seismic measurement results.

The soil amplification datas calculated from the number of blows obtained from Standard Penetration Tests differ between 1.35 - 3.55 but the numbers of blows obtained from Standard Penetration Tests calculated from the microtremors differ between 1 - 6.5 and as we can see the datas received, are bigger.

Shear wave velocities (V_S30) measurements differ between 196 – 432 m/sn, seismic measurements (V_S30) values differ between 179 - 700 m/sn which are calculated by the same methods of the boreholes (SPT-N). Site characteristic period (T₀) differs between 0.24 - 1.20 of seismic measurements and 0.29 - 0.60 from the boreholes.

In the working areas, high amplification and site characteristic period is gained in especially alluvial areas but in the big part of the faced areas of Bakırköy formation there is less soil amplification and site characteristic period.