Probabilistic Seismic Hazard Analysis Of Kathmandu Valley

Abstract

Nepal is located in seismically active region of tectonic plate boundary of Indian plate and Eurasian plate. The location and geological characteristics of Kathmandu valley makes it even more seismically vulnerable. In previous studies, weightage to GMPEs were given with equal probability without any calculative approach. Hence, a rational calculative approach, information theory, is used for the selection and calculation of weightage for GMPEs in this study. Main Himalayan Thrust with both single ramp and double ramp system is modelled and used in logic tree with equal probability along with northern graben as aerial sources. LLH value is calculated for the selection and calculation of weightage for twelve different GMPEs for subduction region out of which only six are selected and used in logic tree. Only one GMPE is selected for active crustal thrust. Seismic hazard map is developed for Kathmandu valley for return period of 475 and 2475 years. The PGA for DBE ranges from 0.26g to 0.42g while for MCE. Significant influence of site effect is observed in central valley. The influence of aerial sources is not significant in Kathmandu valley. Future study incorporating topographic effect and basin edge effect can produce more realistic assessment.