Coda wave attenuation characteristics for the Bilaspur region of Himachal Lesser Himalaya

Seismic wave attenuation is one of the most important parameters that reflect characteristics of the medium traversed by the seismic waves. This parameter is essential for many studies such as determining earthquake source parameters, predicting earthquake strong ground motion, monitoring nuclear explosions and estimating seismic hazard. Since 1995, several region-specific attenuation relations have been developed for the Indian regions, but no such relation is available for the Bilaspur region of the Himachal Lesser Himalaya for the want of data. A six-station local seismological network, deployed in the environs of Koldam site, provided digital recordings of 41 local events occurred in the region from May 2013 to March 2014. This data set has been used to develop the attenuation relations for the region. Majority of the events occurred in the Himachal Lesser Himalaya between the main boundary thrust and the main central thrust. All events have epicentral distances >100 km and magnitudes between 0.5 and 2.9. Adopting the single backscattering model of Aki and Chouet (J Geophys Res 80:3322–3342, 1975 ), coda-Q (Q c ) of the region has been estimated in lapse time windows of 20, 30 and 40 s, respectively. For 30-s lapse time window, the attenuation follows the relation Q c (f) = (70.3 ± 20.27) f (1.23±0.05) for the region. The observed Q c relation is compared with similar relations for seismically active Indian regions and some of the globally available relations. It is found that the average variation of Q c for the Bilaspur region is very close to Amazon Craton (Brazil) due to similar lithologic setup. The variation of ‘Q 0 ’ and ‘n’ values indicates that the region is highly heterogeneous and seismically active. The region is more heterogeneous near the surface as compared to depth. The estimated Q c relations can be utilized for computing source parameters of the local earthquakes and for seismic hazard assessment for the Bilaspur region of Himachal Lesser Himalaya. Copyright Springer Science+Business Media Dordrecht 2015