S-wave attenuation in the Marmara region, northwestern Turkey

Abstract

The frequency-dependent attenuation of shear waves in the crust is estimated by using two different methods based on the rate of time decay of coda-wave amplitude, Q(c)(-1), and the rate of decay of the S-wave to coda wave amplitude ratio with distance, Q(s)(-1). The epicentral distances of selected earthquakes range between 20 and 110 km and magnitudes are around 3. The quality factors, Q(c), are calculated at frequencies of 1.5, 3., 6., 12., and 24. Hz and lapse times of 40, 50, 60, and 70 s. Estimated Q(c) values show a dependence on frequency and lapse time. We observed the similarity in the frequency dependency of Q(c)=(41+/-1.07)f(1.8+/-0.03) and Q(s)=(50+/-1.7)f(1.09+/-0.05) for a lapse time of 50 s indicating that the attenuation mechanism for coda waves is similar to that of the direct S waves.