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 Q^-1_c=(113 ± 7) f^(1.01±0.05) where Q_c is the coda Q parameter. Intrinsic (Q^-1_i) and scattering (Q^-1_s) attenuations was separated using Q_cand direct S-wave Q data (Q_d). It is observed that estimated Q^-1_c is close to Q^-1_i and both of them are much larger than Q^-1_s suggesting that coda decay is predominantly caused by intrinsic attenuation. At higher frequencies, both the attenuation parameters Q_c and, Q_d are similar indicating that coda is predominantly composed of back-scattered S waves at these frequencies.