ATTENUATION RELATIONSHIP FOR NORTH-EAST INDIAN REGION

Abstract

Ground motion attenuation relationship is the most significant and useful topic in engineering seismology. It provides the background for seismic resistant design, seismic zonation map and seismic hazard analysis. Based on strong motion data of Himalayan region, ground motion attenuation relationships were scarcely found in public literatures. And most of the previous attenuation relationships took intensity as an objective, also without consideration of site conditions. In this thesis, strong motion data of North-East Indian region are collected to develop the seismic parameter, e.g. peak ground horizontal acceleration based attenuation relationships and the predictive equations are presented herein. An important component of seismic hazard analysis is to provide a proper model used for predicting the expected ground motion distribution for a possible earthquake scenario, which should consider the characters of earthquake sources, the paths of wave propagation and local site conditions. In this thesis, 254 earthquake recordings were selected with 2 horizontal orthogonal-component seismograms i.e. N-S and E-W, both from National Strong Motion Instrumentation Network database. The widely used ground motion attenuation model is adopted to construct the empirical attenuation equations by two-step regression method proposed by Joyner and Boore [1981]. The predicted peak ground parameters are expressed as a function of magnitude, distance (hypocentral distance) and site category. The model uses a magnitude-independent shape according to geometrical spreading and anelastic attenuation for the attenuation relationships. The final results then are compared with previous attenuation equations proposed for this area.