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Mukhopadhyay, S.
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Mukhopadhyay, S.
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- PublicationRestrictedStudy of attenuation mechanism for Garwhal–Kumaun Himalayas from analysis of coda of local earthquakes(2010)
; ; ; ; ;Mukhopadhyay, S.; Department of Earth Sciences, IIT Roorkee, Roorkee, Uttaranchal 247667, India ;Sharma, J.; 70/11-A, Purvawali Ganesh Chowk, Roorkee-247667, India ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Kumar, N.; Wadia Institute of Himalayan Geology, General Mahadeo Singh Road, Dehradun-248001, India; ; ; The relative contribution of intrinsic (Q−1 i ) and scattering (Q−1 s ) attenuation to seismic wave attenuation was estimated for the Garwhal–Kumaun Himalayas using Multiple Lapse Time Window Analysis (MLTWA) method under the assumption of isotropic scattering. Local earthquake data recorded by an array operated by Wadia Institute of Himalayan Geology (WIHG), India was used for this purpose. It is observed that scattering attenuation primarily contributes to seismic wave attenuation in this region and its value is much higher compared to that of intrinsic attenuation at around 1Hz frequency. As frequency increases the relative contribution of scattering attenuation to total attenuation starts decreasing. However, as seismic albedo is higher than 0.5 for all the frequencies considered, it is concluded that the medium here is highly heterogeneous in nature141 26 - PublicationRestrictedThe attenuation mechanism of S-waves in the source zone of the 1999 Chamoli earthquake(2014)
; ; ; ; ; ;Mukhopadhyay, S.; Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India ;Kumar, A.; Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India ;Garg, A.; Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India ;Del Pezzo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Kayal, J. R.; School of Oceanographic Studies, Jadavpur University, Kolkata 700016, India; ; ; ; In the present study the attenuation mechanism of seismic wave energy in and around the source area of the Chamoli earthquake of 29th March 1999 is estimated using the aftershock data. Most of the analyzed events are from the vicinity of the Main Central Thrust (MCT), which is a well-defined tectonic discontinuity in the Himalayas. Separation of intrinsic (Q 1 i ) and scattering (Q 1 s ) attenuation coefficient is done over the frequencies 1, 2, 4, 8 and 16 Hz using Multiple Lapse Time Window Analysis (MLTWA) method. It is observed that S-waves and their coda are primarily attenuated due to scattering attenuation and seismic albedo is very high at all the frequencies. A comparison of attenuation characteristics obtained using these aftershock data with those obtained using data of general seismicity of this region reveal that at lower frequencies both intrinsic and scattering attenuation for Chamoli was much higher compared to those for Garwhal-Kumaun region using general seismicity data. At higher frequencies intrinsic attenuation for Chamoli is lower than and scattering attenuation is comparable to those obtained using general seismicity data of Garwhal-Kumaun region.301 64