Attenuation studies based on local earthquake Coda waves in the southern Indian peninsular shield

The Dharwar craton, Cuddapah basin and the Godavari graben characterise three diverse geological and tectonic settings in the peninsular shield of India. Owing to their contiguous proximity, they offer a unique opportunity to document differences, if any, in their seismic wave attenuation characteristics that might have a bearing on the seismogenic nature of the crust in a craton, basin and a rift-like graben structure. An attempt is made here to bring out these differences using constraints from coda-Q. We considered local earthquakes with epicentral distances ranging from␣14 to 150 km recorded at the digital broadband stations at Dharwar (DHD), Cuddapah (CUD) and Kothagudem (KGD) regions to derive the frequency-dependent coda-Q relations. Using the single scattering method, we obtained the frequency-dependent Q <Subscript>C</Subscript> relationship (Q <Subscript>C</Subscript> = Q <Subscript>0</Subscript> f <Superscript> n </Superscript>)for each of the three geological units separately: DHD: Q <Subscript>C</Subscript> = (730.62 ± 0.09)f <Superscript>(0.54 ± 0.01)</Superscript>; CUD: Q <Subscript>C</Subscript> = (535.06 ± 0.13)f <Superscript>(0.59 ± 0.01)</Superscript> and KGD: Q <Subscript>C</Subscript> = (150.56 ± 0.08)f <Superscript>(0.91 ± 0.01)</Superscript>. The Q <Subscript>C</Subscript> values obtained for all the three sub-regions show moderate to strong frequency dependence and essentially reflect the level of crustal heterogeneities to varying degrees. Copyright Springer Science+Business Media B.V. 2007