A Frequency-dependent Relation of Coda Qc for Koyna-Warna Region, India

Attenuation properties of the lithosphere around the Koyna-Warna seismic zone is studied by estimating the coda-Qc from 30 local earthquakes of magnitude 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 114 km. The estimated Qc values show a frequency-dependent relation, Qc 169 f0.77, 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 active regions is low as compared to that for stable regions. However, South Carolina and Norway are exceptions in that their Q is low in the low frequency 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 Garhwal Himalaya (STIH), in the higher frequency range. In contrast to this, the 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.