PROBABILISTIC SEISMIC HAZARD ASSESSMENT

Abstract

The seismic hazard assessment is concerned with the estimation of strong-motion parameters at a site for the purpose of seismic safety assessment. It involves estimation of the earthquake related phenomena such as ground shaking, fault rupture, ground failure or soil liquefaction at a site. For the reliable assessment of the seismic hazard at a site the level of ground shaking can be characterized by various types of ground motion parameters and estimated in terms of peak Ground Acceleration (PGA) and Spectral Acceleration (Sa). In the present study Probabilistic Seismic Hazard Analysis (PSHA) has been carried out for the region of North-East India, which is one of the most seismically active region of India. For this purpose, the study area is divided into eight seismogenic source zones based on geology, tectonics and seismicity in and around the region of North-East India. And by using Gutenberg-Richter recurrence relationship, the seismic hazard parameters such as a, b and Magnitude of completeness, M has been completed for sources zones. Also, all seismic hazard parameters have been computed by combining all source zones into single source zone. An attenuation model proposed by Abrahamson and Silva (1997), Abranhamson and Silva (2007), Akkar and Bommer (2007), Boore and Atkinson (2008), Akkar and Bommer (2010), Arroyo et al., (2010), Idriss (2008) and Lin and Lee (2008)are employed.The PGA and PSA values are computed for different attenuation models and also in Akkar and Bommer(2007) considering for 2%, 5%, 10% damping for the probability of exceedance in 50 years and Average pga results. The computed PGA and PSA values of the region are shown in the fallowing map by usingArcGlS10.According to Abrahamson and Silva (2007) and Akkar and Bommer (2010) attenuation models the estimated PGA values are higher in the source Zones-I, 11 and VIII. In source Zones-I and VI! there exists Shillong Plateau and Himalaya which are hard rocks but in source zone-Il mainly Bangladesh have soil amplification.