Seismic Source Parameters and High-Frequency Spectral Decay Model for the Region of North India

This study examines the seismic source parameters and high-frequency spectral attenuation factor (kappa) of 36 minor to moderate earthquake (EQ) events that have been occurred in the north-west Himalayas and its foothills of north India from 2007 to 2016. A non-reference generalised inversion technique has been used to compute the source spectra, and the point source model is used to estimate the seismic moment (M0) and corner frequency (fc). Further, a scaling relation between M0 and fc has been developed for the study area. Additionally, based on the determined fc and M0 values, source characteristics such as seismic energy (Es), stress drop (Delta sigma) and apparent stress drop (sigma a) are estimated for each of the 36 events. In the present work, sigma a and triangle sigma were found to range from 0.1 MPa to 12.36 MPa and 0.17 MPa to 14.61 MPa, respectively. Low values of sigma a and triangle sigma can be associated with the low effective stress model EQs. Furthermore, a majority of EQs appear to have a partial stress drop mechanism according to the Z & uacute;& ntilde;iga parameter (epsilon) determined for the region. Also, the parameter kappa\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\boldsymbol{\kappa}}$$\end{document} is estimated and is found to range between 0.015 and 0.071 for the horizontal component, and 0.01 and 0.036 for the vertical component. The epicentre distance for various site classes is used to construct a regional model for kappa. Finally, stochastic ground motion simulations of historical EQ records utilising estimated source parameters and constructed kappa models are performed in order to validate the findings of the present work. The comparison of the original and simulated EQ records is in very good agreement, demonstrating the efficacy of the obtained parameters in capturing the local ground motion features.