Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Investigation Of Sıte Charactherıstıcs Of Avcılar Regıon By Usıng Geophysıcal Methods

Avcılar district was the most affected region in İstanbul, from the large earthquakes that occured on 17 Agust and 12 November 1999 respectively in Kocaeli and Düzce. Although being located aproximately 100 km away from the epicenter of 17 August earthquake, the district was severely damaged, 273 people died and 630 were injured. Economical losses to structures can be listed such that, 158 buildings had been out of use, 526 were moderately damaged, and 800 of them had light damage.

As the increase in the probability of an earthquake in the Marmara Sea is evident, studies on the investigation of site characteristics in the vicinity of Avcılar district is increased where most of the damage is expected. In this work, site characteristics of the Avcılar district and its vicinity is evaluated.

As a result of the analysis of 234 DES measurements recorded in the various parts of the work area, subsurface apparent resistivity maps are prepared for the corresponding depths of 5, 10, 15, 20, 25 meter which show change of the distribution of resistivity parameter.

141 borehole data for various locations are analysed and Vs velocities are derived by the relationship between SPT-N and Vs values. Finally, shear wave velocity distribution map is obtained for 5, 10, 15, 20, 25 meter depths. 67 of the boreholes at available depths are analysed to obtain Vs₃₀ velocities to plot the subsurface maps. By using these velocity distribution maps NEHRP2000, EURO CODE 8 and UBC type classifications are obtained.

Site amplification values are calculated by some amprical relations for Vs which are based on the relationship between SPT-N and Vs parameters. Work area is categorized by the risk level using site amplification values. Additionally, 192 seismic refraction measurement is analysed to calculate and map the fundamental mode and Poisson Ratio distributions and also, fundamental modes are calculated by microtremor records and mapped.

As the subsurface resistivity map for the 5 m is prepared, it is observed that rocks with high resistivity ranging between 90-200 Ohm.m is northward distributed and also 20 to 90 Ohm.m values are densely located in south. High resistivity values are observed in the central and southern part for depths larger than 5 meters. Shear wave velocity distribution map indicates that higher velocities (320-440 m/s) are frequently observed in the northern and central part at depths shallower than 5 meters. Southern part of the work area has higher velocities for depths larger than 5 meters. Site amplification maps shows that amplification values ranging between 1.60 to 3.1 is observed in the work area. Lower fundamental mode values between 0.15-0.30s is observed in the northern part and higher values 0.75-0.95s are observed in the southern part.

KILIÇ Selçuk ,

Danışman :Prof.Dr.Yıldız ALTINOK

Anabilim Dalı :Jeofizik Mühendisliği

Programı (Varsa) :

Mezuniyet Yılı :2006

Tez Savunma Jürisi : Prof.Dr.Yıldız ALTINOK (Danışman)

Prof.Dr.İlhan OSMANŞAHİN

Prof.Dr.Demir KOLÇAK

Prof.Dr. Ali PINAR

Doç.Dr.Nurcan ÖZEL