[S-SS23_1AM2] Strong Ground Motion and Earthquake Disaster

[SSS23-10] DETERMINATION OF S-WAVE VELOCITY STRUCTURE BY MICROTREMOR ARRAY OBSERVATION IN TEKIRDAG AND ZEYTINBURNU (TURKEY)

*Ozlem KARAGOZ¹, Seckin ozgur CITAK², Kosuke CHIMOTO¹, Hiroaki YAMANAKA¹, Oguz OZEL³, Esref YALCINKAYA³, Hussam ZANEIH¹, Aysegul ASKAN GUNDOGAN⁴, Kojima KAOURU¹, Tsuchiya TOMOHIRO¹, Behiye AKSAHIN³, Sena ILKAY³, Fatma SISMAN DERAN⁴ (1.Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 2.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.Istanbul University,Department of Geophysical Engineering, Turkey, 4.Middle East Technical Uni.,Dept .of Civil Engineering and Dept. of Earthquake Studies,Turkey)

Keywords:Microtremor, Spac, S-wave velocity, Tekirdag, Zeytinburnu, Turkey

The use of environmental vibration recordings (microtremors) is cost effective and easily collected data for site characterization that is a component of microzonation mapping and has become very popular around the world in the last years.Local site conditions have a major effect on the level of ground shaking. For this reason we carried out microtremor measurements by using circular small array configuration at twenty one locations in Tekirdag, four locations in Zeytinburnu and one location in Yesilkoy. In addition to eight large array measurements for estimating S-wave velocity structures of shallow deeper soil formations for site effect analysis. These sites were selected by considering the different geological units (i.e. recent landfill, clay stone, silt stone, alluvium, lime stone, sand) in the cities. We also collected data on five buildings in Tekirdag in order to understand dynamics properties of buildings. We estimated the phase velocities of Rayleigh waves at each site from the vertical components of recorded microtremor data by using Spatial Autocorrelation (SPAC) method. Obtained phase velocity dispersion curves are varied from area to area. The obtained phase velocities range from 100 m/s to 750 m/s along the coastline in Tekirdag while, they range from 200 m/s to 500 m/s for Zeytinburnu area. Genetic Simulated Annealing Algorithm technique was applied for inversion of phase velocities to estimate 1-D S-wave velocity structures beneath the sites. The inverted Vs profiles are not uniformed. The preliminarily results show that similar phase velocity changes have been seen at the low and the high periods on the different geological units along the parallel direction of the coastline. When we check the velocity changes from coastline toward the inland, we can see the different phase velocities on the different geological units.