Rethinking communication in risk interpretation and action

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.