Site attenuation and source parameters on the North Anatolian Fault zone, eastern Turkey estimated from the aftershocks of 13 March 1992 Erzincan earthquake |
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| Authors: | Haluk Eyidogan Aybige Akinci |
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| Institution: | (1) Maden Fakultesi, Jeofizik Muhendisligi Bolumu, Istanbul Teknik Universitesi, 80626 Maslak-Istanbul, Turkey, e-mail;(2) Dokuz Eylul Universitesi, Muhendislik Fakultesi, Jeofizik Muhendisligi Bolumu, 35100 Bornova-Izmir, Turkey |
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| Abstract: | Site attenuation and source characteristics of 45 aftershocks of the 13 March 1992 Erzincan, eastern Turkey earthquake have been determined from SH-wave spectra using a least-squares best-fit method. Although the most of the seismograms were recorded on the ophiolitic rock sites and the average regional attenuation correction of Q(f) = 35 f0.83 was applied, the high fall-off rates  ranging between 3.0 and 4.5 beyond the corner frequencies of 8–13 Hz were observed on the SH spectra. The site attenuation value,  , has been calculated from the slope of the high frequency part of the SH spectra. It was found that varied in the range of 0.0124–0.0364 s and the average was 0.0246 s with a standard deviation of 0.0047 s. The high fall-off rates of observed spectra have decreased considerably as a result of site attenuation corrections and converged to an average value of 2.3. We concluded that the high fall-off rates of SH wave spectra are mainly controlled by highly deformed Miocene ophiolitic formations which covers a wide area in the North Anatolian Fault zone in the vicinity of Erzincan region. Using the spectra that were corrected for regional and site attenuation, and assuming a Brune's source model; seismic moment, source radius, and stress-drops of the aftershocks were computed. We found that stress-drops for some of the aftershocks in Erzincan area have slightly decreased after removal of site attenuation over SH wave observed spectra. |
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| Keywords: | earthquake source parameters regional and site attenuation source spectrum spectral fall-off rate |
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