P- AND S-WAVE ATTENUATION IN THE KOPILI REGION OF NORTHEASTERN INDIA

We comprehensively analyze attenuation factor in Kopili region and its neighboring area. Corresponding to influence of frequency on attenuation, Q(P) and Q(S) are estimated from direct P and S waves. The results establishes higher values of Q for S waves (Q(S)=(101 +/- 4) f(1.4 +/- 0.05)) than for P waves (Q(P)=(45 +/- 3)f(1.3 +/- 0.07)) in the 1.5-12 Hz frequency band. It is seen that our findings agree with other published results on tectonically active regions that is characterized by high degree of heterogeneity. Hence, it can be useful for further studies in ground motion prediction in Kopili region. The low value of quality factors corresponding to P and S waves refers to seismically actives areas with complex heterogeneity. The estimated value of Q(S)/Q(P) and their subsequent association with frequency affirm the dominance of scattering as a major contribution to diminution of seismic amplitudes. This is further corroborated by local geological settings.