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

In the present study, the scattering and intrinsic attenuation are separated using the S-wave attenuation (Q(beta)) 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(alpha)) and the S wave (Q(beta)) are estimated using the extended coda-normalization method of Yoshimoto et al. (1993). The frequency dependence Q(alpha) and Q(beta) relationships are obtained as Q(alpha) = (25 +/- 1)f((1.24 +/- 0.04)) for the P wave and Q(beta) = (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(beta) and Q(c) with Q(i) and Q(s) shows that both Q(i) and Q(s) are lower than the Q(beta), 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(beta); 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(beta).