Frequency-Dependent Attenuation of Coda Waves in the Crust in Southwest Anatolia (Turkey)

摘要

The attenuation of coda waves in the earth's crust in southwest (SW) Anatolia is estimated by using the coda wave method, which is based on the decrease of coda wave amplitude in time and distance. A total of 159 earthquakes were recorded between 1997 and 2010 by 11 stations belonging to the KOERI array. The coda quality factor Q_c is determined from the properties of scattered coda waves in a heterogeneous medium. Firstly, the quality factor Q_0 (the value of Q_c at 1 Hz.) and its frequency dependency g are determined from this method depending on the attenuation properties of scattered coda waves for frequencies of 1.5, 3.0, 6.0, 8.0, 12 and 20 Hz. Secondly, the attenuation coefficients (δ) are estimated. The shape of the curve is controlled by the scattering and attenuation in the crustal volume sampled by the coda waves. The average Q_c values vary from 110 ± 15 to 1,436 ± 202 for the frequencies above. The Q_0 and g values vary from 63 ± 7 to 95 ± 10 and from 0.87 ± 0.03 to 1.04 ± 0.09, respectively, for SW Anatolia. In this region, the average coda Q-f relation is described by Q_c = (78 ± 9)f~(0.98±0.07) and d = 0.012 km~(-1). The low Q_0 and high g are consistent with a region characterized by high tectonic activity. The Q_c values were correlated with the tectonic pattern in SW Anatolia.