Frequency-dependent attenuation of P and S waves in northeast India

Abstract

We have analysed 202 seismograms recorded at 10 seismic stations in the northeast (NE) India region to infer the frequency-dependent attenuation characteristics of both P and S waves, in the frequency range from 1.5 to 24 Hz and in the distance range from 30 to 100 km. We used extended coda-normalization method to determine the attenuation of P wave (Q-1P) and S wave (Q-1S). The results show that both P and S waves undergo a strong attenuation along ray paths. The values of Q-1P and Q-1S, corresponding to spectral amplitude decays, show strong frequency dependence and are expressed as Q-1P= (0.035 ± 0.014)f-(0.96±0.01) and Q-1S= (0.014 ± 0.006)f-(0.94±0.03), respectively, in 1.5-24 Hz. The ratio Q-1P/Q-1S is found to be larger than unity for the whole frequency range. The high frequency dependence of both P- and S waves indicate the highest attenuation among the world at lower frequencies. © 2010 The Authors Geophysical Journal International © 2010 RAS.