ATTENUATION OF CODA WAVES IN WESTERN ANATOLIA

By analyzing the decay of coda wave amplitude, we have determined coda Q,Q(c), in Western Anatolia (Turkey). Using the single isotropic scattering model, we analyzed 116 earthquakes which registered at the Gebze station by using five narrow frequency bands centered at 1.5, 3, 6, 8 and 10 Hz. Coda Q values were obtained using different lapse times, between 30 and 190 s, in steps of 10 s. Coda Q(c) for Western Anatolia depends on frequency and lapse time. For a lapse time of 30 s, the frequency dependence of Q(c) is Q(c)(f) = 50.7f1.01 and for a lapse time of 190 s it is Q(c)(f) = 183.2f0.76. In this region, the exponential value of the Q(c) frequency dependence is practically constant, between 0.7 and 1.0. The obtained coda Q(c) values were compared with those estimated in other regions. The coda Q(c) values for lapse times between 60 and 100 s for Western Anatolia and Southern Spain are practically the same, indicating similar coda wave attenuation patterns in both regions of the Mediterranean Basin.