The Attenuation of High‐Frequency Seismic Waves in the Lower Siang Region of Arunachal Himalaya:Qα,Qβ,Qc,Qi, andQs

Abstract

In the present study, the scattering and intrinsic attenuation are separated using the S ‐wave attenuation ( Q β ) and coda‐wave attenuation ( Q c ) employing the Wennerberg (1993) method, and the frequency‐dependent Q s and Q i relations have been developed for the region. The Q i and Q s show the frequency‐dependent character in the frequency range 1.5–24 Hz. The average scattering and intrinsic relationships are obtained for the region as Q s =(31±1) f 1.04±0.02, Q s =(48±1) f 1.05±0.02, and Q s =(61±1) f 1.05±0.02 and as Q i =(68±1) f 0.95±0.06, Q i =(134±1) f 1.01±0.05, and Q i =(167±1) f 0.96±0.03 for lapse time windows of 30, 40, and 50 s, respectively. The quality factor for the P wave ( Q α ) and the S wave ( Q β ) are estimated using the extended coda‐normalization method of Yoshimoto et al. (1993). The frequency dependence Q α and Q β relationships are obtained as Q α =(25±1) f (1.24±0.04) for the P wave and Q β =(58±1) f (1.16±0.04) for the S wave. The quality factor for the coda wave ( Q c ) is estimated using the single backscattering model of Aki and Chouet (1975). The comparison of Q β and Q c with Q i and Q s shows that both Q i and Q s are lower than the Q β , as well as Q c , at 30 s lapse time. As the lapse time increases, both Q i and Q s increase in such a manner that Q c will increase because it contains the effects of both. This agrees with the theoretical as well as the laboratory measurements. Also Q c is higher than Q β ; this supports the model given by Zeng et al. (1991), which predicts that the combination of Q i and Q s should be such that Q c is more than Q β .