Attenuation mechanism of seismic wave in Chamoli region of Garhwal-Kumaun Himalayas

Abstract

In this study the S-wave attenuation mechanism is analyzed and intrinsic and scattering attenuation effects are separated. This helps in understanding the physical mechanisms governing attenuation properties of the crust of this region. It has been observed that the Qs-1, Qd-1 and Qc-1 values at all frequencies are comparable. The estimated Le-1, B0, Qi-1, Qs-1, Qd-1 and Qc-1 values show that S-wave attenuation is primarily controlled by scattering attenuation in the source zone of the 1999 Chamoli earthquake. My results also show that for the source zone of 1999 Chamoli earthquake in the Garhwal Himalayas seismic albedo is very high, i.e. attenuation is mainly controlled by scattering attenuation. In conclusion, The extinction length Le varies between about 12 km to about 125 km in the study region. The seismic albedo (B0) values vary between 0.65 and 0.8. B0 values are very large (>0.5) showing that at all frequencies scattering attenuation is the dominating factor causing attenuation of seismic waves. This shows that the degree of heterogeneity is very high for the frequency range considered in this area. © 2010, European Association of Geoscientists and Engineers.