Abstract
We have studied the attenuation characteristics of eastern Himalaya and southern Tibet by using local earthquake data set that consists of 123 well-located events, recorded by the Himalayan Nepal Tibet Seismic Experiment operated during 2001–2003. We have used single backscattering model to calculate frequency-dependent values of coda Q ( $$Q_\mathrm{c}$$ ). The estimation of $$Q_\mathrm{c}$$ is made at central frequencies 2, 4, 8 and 12 Hz through five lapse time windows from 10 to 50 s starting at double the travel time of the S-wave. The observed $$Q_\mathrm{c}$$ is found to be strongly frequency-dependent and follows a similar trend as observed in other tectonically active parts of the Himalaya. The trend of variation of $$Q_\mathrm{c}$$ with lapse time and the corresponding apparent depths is also studied. Increase in $$Q_\mathrm{c}$$ values with the lapse time suggests that the deeper part of the study region is less heterogeneous than the shallower part. The observed values of $$Q_0$$ ( $$Q_\mathrm{c}$$ at 1 Hz) and frequency parameter n indicate that the medium beneath the study area is highly heterogeneous and tectonically very active. A regionalization of the estimated $$Q_0$$ is carried out, and a contour map is prepared for the whole region. Some segments of Lesser Himalaya and Sub-Himalaya exhibit very low $$Q_0$$ , while the whole Tethyan Himalaya and some parts of Greater Himalaya are characterized by low $$Q_0$$ values. Our results are comparable with those obtained from tectonically active regions in the world.
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