Estimation of Coda Wave Attenuation in the East Anatolia Fault Zone, Turkey

In this study, the attenuation of coda waves Q (c)(f) has been estimated for different lapse times and frequencies in the East Anatolian Fault Zone (EAFZ) in Turkey using a single back-scattering model of S-coda envelopes. The data include 255 earthquakes recorded by ten stations. The frequency-dependent Q (c) values are estimated at central frequencies of 1.5, 3, 6, 8, 12, and 18 Hz using 20-30-40 s lapse time windows. Along this fault zone, the frequency-dependent Q (c) obtained for all data and lapse time is Q (c) = 57.5f (0.82). The entire study area is divided into six subregions according to the magnitude of the earthquakes and the location of the fault segments. The estimated average frequency-dependent relation for all lapse times are; for Bingol-Karliova-Erzincan triple junction; for Bingol-Lake Hazar segment; for Lake Hazar-Sincik segment; Hazar-Sincik and Celikhan-GolbaAYA +/- faults; for Kahramanmaras triple junction and for Amanos Range and Karasu Basin. The lowest Q (c) is determined between Bingol and Malatya. The highest Q (c) value is along Amanos Range. In addition, Q (c) values are calculated for each regions at different lapse times. The average Q (c) value of the study region varies from 53 +/- A 11 at 1.5 Hz to 498 +/- A 41 at 18 Hz for 20 s lapse time window, as its variation is from 116 +/- A 11 at 1.5 Hz to 749 +/- A 75 at 18 Hz of central frequency for 40 s lapse time window. The increase of Q (c) with lapse times changes from one subregion to another along the fault zone. The rate of increment is significantly higher in Bingol-Karliova-Erzincan triple junction than in the other subregions. This rapid increase of low Q (c) values in the junction reaches the general attenuation characteristics of the fault at 40 s lapse time. Finally, the low Q (0) and high n values can be attributed to the energy loss as a result of the heterogeneity and activity along the fault zone. The increase of Q (c) with frequency, lapse time may be related to heterogeneity decreases with depth. The rapid increase of Q (c) with depth in Bingol-Karliova-Erzincan triple junction may be interpreted that the effect of the Northern Anatolian Fault Zone is effective in the upper crust is not so deep compared to EAFZ.