Study of attenuation mechanism for Garwhal–Kumaun Himalayas from analysis of coda of local earthquakes

Abstract

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 nature