Seismic Hazardand Spectral Acceleration For Hydro Power Project in Gilgit Baltistan Pakistan

Abstract

Peak ground acceleration is the maximum ground shaking intensity parameter in geophysics. To prevent the big loss of infrastructure, dam site or multistorey buildings as well as power project due to any seismic hazard, it is essential to mitigate the damages. Seismic hazard analysis for peak ground acceleration was carried out for hydropower project in Gilgit Baltistan to mitigate the effect of seismic hazard. Seismicity and tectonic map was drawn for distribution of seismic events.Study region was divided into seven source zones to rectify the seismic risk reduction assessmement of the region. Regression analysis for freqeuncy magnitude was also carried out using seismicity catalogue. Three distinct ground motion equations were used to predict the value of g with their return period. The actitvity rate analysis of seismic source zones was also done drawn to determine the source contribution. Maximum credible earhquake, operational based earthquake and maximum design earthquake were detremined. According to the ICOLD and seismic risk reduction policy, the values of peak ground acceleration for Phandar hydro power project was 0.59g for maximum credible earthquake, for design basis earthquake g value was 0.311g for and 0.231g foroperational basis earthquake with 475 years of return period at 50% probability of exceedence. Spectral acceleration for 0.1s, 0.2s, 0.5s, 1s and 2s was also computed for horizontal and vertical components. The values of spectral accleeration varied from 0.19g to 1.250g for maximum credible earthquake, 0.019g to 0.700g for design based earthquake and 0.050g to 0.480g for operational based earthquake. The results reveal that the maximum credible earthquake is to ensure safety level and for reliability level, operational based and design based earthquakes can be utilized.