High frequency ground motion scaling in eastern Turkey

Abstract

A regional study of ground motion scaling parameters is presented for the region surrounding the eastern Turkey. The data set used in this study consists of 100 earthquake events from Eastern Turkey Seismic Experiment (ETSE) network with the magnitudes between (ML and Mw) 3.0 - 5.5. All selected events are in the upper crust. In order to emprically obtain the scaling relationships for high frequency S-wave motion, regressions are carried out on three component broadband seismograms, all recorded within a hypocentral distance of 400 km to emprically obtain the scaling relationships for the high ' frequency S-wave motion. The signals were processed to examine the peak ground velocity and Fourier velocity spectra in the frequency range of 0.3 - 10 Hz. Random vibration theory (RVT) is used to test estimates of the peak ground motion in the time domain. Comparison of the two regressions indicated both regression results display consistent shapes. Geometrical spreading function g(r), characterized by: g(r) = r-Lo for r ~ 40 km, r0 is used for 40~ r ~ 100 km and { 0 · 5 is used for r 2: 100 km. A very low quality factor, Q(f) = 50fl·75 is used to described the anel~stic crustal attenuation in the region. Excitation terms are well matched. An effective high-frequency, distance independant spectral parameter, Kerr= 0.035 sec, is obtained in this study. Both regressions show that eastern Turkey region has very high attenuative properties.