Microtremor measurements at Kadıköy-Üsküdar districts of Istanbul

Abstract

Microtremor has been utilised in seismic microzonation as aneffective tool to estimate local geological conditions.To determine the predominant frequencies of the Kadlkoy -UskUdar districts of Istanbul and to create a microzonation map forthis selected area, microtremor measurements were carried out at 63sites during the period of September - October 1993 using portable1-sec period Ranger type of three-component seismometer. Themicrotremor measurements were taken at a sampling rate of 1/50second for a time span of 40.96 seconds and repeated three timesat every measurement points. In an endeavour to minimize highartificial disturbances effects on records in a day time, it wasdecided to take late-night measurements, between 2330 p.m. and 0530a.m., for each points.Data were analysed using Kobayashi's Running Fourier Spectrum.Kanai 's Second Proposal was used to classify the ground underlyingstudy area.The predominant frequencies of these parts of Istanbul weremostly overcomed. The study area has predominant frequenciesbetween 4.5 Hz and 8 Hz.