The attenuation mechanism of seismic waves in northwestern Himalayas

Abstract

We analysed local earthquake waveforms recorded on a broad-band seismic network in northwestern Himalayas to compute the intrinsic and scattered attenuation parameters from coda waves. Similar to other tectonically active and heterogeneous regions, attenuation-frequency relation for western Himalaya is Qc-1 = (113 ± 7) f(1.01±0.05) where Qc is the coda Q parameter. Intrinsic (Qi-1) and scattering (Qs-1) attenuations was separated using Qc and direct S-wave Q data (Qd). It is observed that estimated Qc-1 is close to Qi-1 and both of them are much larger than Qs-1 suggesting that coda decay is predominantly caused by intrinsic attenuation. At higher frequencies, both the attenuation parameters Qc and, Qd are similar indicating that coda is predominantly composed of back-scattered S waves at these frequencies. © 2006 The Authors Journal compilation © 2006 RAS.