A frequency-dependent relation of coda Q(c) for Koyna-Warna region, India

Attenuation properties of the lithosphere around the Koyna-Warna seismic zo ne is studied by estimating the coda-Q(c) from 30 local earthquakes of magn itude varying from 1.5 to 3.8. An average lapse time of 65 sec used in the single scattering model sampled a circular area with an average radius of 1 14 km. The estimated Q(c) values show a frequency-dependent relation, Q(c) = 169 f(0.77), and range from 169 at 1 Hz to 1565 at 18 Hz. A comparison of worldwide Q studies reveals that for a large frequency range the Q for act ive regions is low as compared to that for stable regions. However, South C arolina and Norway are exceptions in that their Q is low in the low frequen cy range while New England and North Iberia are exceptions as they have a Q value similar to that for active regions like Spain, Turkey, Italy and Gar hwal Himalaya (STIH), in the higher frequency range. In contrast to this, t he Q for the Koyna-Warna area, which belongs to a stable region, is low in the entire frequency range as compared to the stable regions and similar to the active STIH regions.