HAZARIKA, D and Baruah, S and Gogoi, N K (2009) Attenuation of coda waves in the Northeastern Region of India. J Seismology, 13. pp. 141-160.

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Coda wave attenuation quality factor Qc is estimated in the northeastern region of India using 45 local earthquakes recorded by regional seismic network. The quality factor Qc was estimated using the single backscattering model modified by Sato (J Phys Earth 25:27–41, 1977), in the frequency range 1–18 Hz. The attenuation and frequency dependence for different paths and the correlation of the results with geotectonics of the region are described in this paper. A total of 3,890 Qc measurements covering 187 varying paths are made for different lapse time window of 20, 30, 40, 50, 60, 70, 80, and 90 s in coda wave. The magnitudes of the analyzed events range from 1.2 to 3.9 and focal depths range between 7 and 38 km. The source–receiver distances of the selected events range between 16 and 270 km. For 30-s duration, the mean values of the estimated Qc vary from 50 ± 12 (at 1 Hz) to 2,078 ± 211(at 18 Hz) for the Arunachal Himalaya, 49 ± 14 (at 1 Hz) to 2,466 ± 197 (at 18 Hz) for the Indo-Burman, and 45 ± 13 (at 1 Hz) to 2,069 ± 198 (at 18 Hz) for Shillong group of earthquakes. It is observed that Qc increases with frequency portraying an average attenuation relation Qc = 52.315 ± 1.07 f (1.32±0.036) for the region. Moreover, the pattern of Qc−1 with frequency is analogous to the estimates obtained in other tectonic areas in the world, except with the observation that the Qc−1 is much higher at 1Hz for the northeastern region. The Qc−1 is about 10−1.8 at 1 Hz and decreases to about 10−3.6 at 18 Hz indicating clear frequency dependence. Pertaining to the spatial distribution of Qc values, Mikir Hills and western part of Shillong Plateau are characterized by lower attenuation.

Item Type: Article
Subjects: Geo Science > Seismology
Depositing User: Dr. PK Barooah
Date Deposited: 09 Jan 2012 05:45
Last Modified: 09 Jan 2012 05:46
URI: http://neist.csircentral.net/id/eprint/109

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