Determination of S and Coda Wave Attenuation in Selected Regions of Lower and Northern Assam Within North Eastern India

Abstract

The North Eastern (NE) regions of India has been subjected to vicious damages due to numerous earthquakes. Thus, seismological study in this part of India has been a priori for a long period of time. Present study focuses to find the attenuation characteristics of selected regions within NE India. These selected regions include Guwahati and Kokrajhar from the lower Assam along with Tezpur and Nagaon from the northern Assam. The attenuation characteristics are shown in terms of frequency $$\left( f \right)$$ dependent quality factor $$\left( Q \right)$$ obtained based on the attenuation of S and coda wave from regional ground motion records. $$Q - f$$ correlations $$\left( {i.e. \,Q\left( f \right) = Q_{o} f^{\eta } } \right)$$ are determined from the recorded ground motions in Guwahati, Tezpur, Nagaon and Kokrajhar regions. Obtained S wave attenuation for Guwahati, Tezpur, Nagaon and Kokrajhar are $$176f^{1.126}$$ , $$353f^{0.685}$$ , $$204f^{0.886}$$ and $$208f^{0.526}$$ respectively. On the other hand, due to limited ground motion records for the analysis, coda wave attenuation is obtained only for Tezpur and Nagaon regions as $$106f^{1.119}$$ and $$100f^{1.086}$$ respectively. Obtained attenuation characteristics help to understand the tectonic diversity along with the scale of medium heterogeneity present in this above study region. Further, above obtained attenuation characteristics are very essential for building a synthetic ground motion model for the selected regions, in order to generate probable seismic scenario as well as for the seismic hazard assessment.