Estimation of path attenuation and site characteristics in the north-west Himalaya and its adjoining area using generalized inversion method

Abstract. Present work focuses on the determination of path attenuation as well as site characteristics of PESMOS managed recording stations, located in the north-west Himalaya and its adjoining region, using two-step generalized inversion technique. In the first step of inversion, non-parametric attenuation curves are developed. Presence of a kink is observed at around 105 km hypocentral distance while correlating the path attenuation with the hypocentral distance indicating the presence of Moho discontinuity in the region. Further, Q_s = 105 f^0.94 as S wave quality factor within 105 km, is obtained indicating that the region is possibly heterogeneous as well as seismically active. In the second step of inversion, site amplification curves are developed separately from the attenuation corrected data for horizontal and vertical components of the accelerogram. Further, site amplification spectra is computed as the ratio of the obtained horizontal and vertical components to determine the amplification function and predominant frequency for each of the PESMOS managed recording stations, exist within the study area. The predominant frequency based on generalized inversion method and based on horizontal to vertical spectral ratio of S wave portion of the accelerogram matches well. Maps showing spatial distribution of predominant frequencies and amplification functions across the study region are also developed based on the present work.