An Improved Probabilistic Seismic Hazard Assessment of Tripura, India

The state of Tripura lies in northeast India, which is considered one of the most seismically active regions of the world. In the present study, a realistic probabilistic seismic hazard assessment (PSHA) of Tripura state is presented based on improved seismogenic sources considering layered polygonal sources corresponding to hypocentral depth ranges of 0-25, 25-70 and 70-180 km, respectively, and data-driven selection of suitable ground motion prediction equations (GMPEs) in a logic tree framework. Analyses are carried out by formulating a layered seismogenic source zonation together with smooth-gridded seismicity. Using the limited accelerogram records available, the most suitable GMPEs are selected after performing a thorough quantitative assessment, and thus the uncertainty in selecting appropriate GMPEs in PSHA is addressed by combining them with the proper weight factor. The computations of seismic hazard are carried out in a higher-resolution grid interval of 0.05 degrees x 0.05 degrees. The probabilistic seismic hazard distribution in terms of peak ground acceleration (PGA) and 5% damped pseudo-spectral acceleration (PSA) at different time periods for 10% and 2% probability of exceedance in 50 years at engineering bedrock level are presented. The final results show significant improvements over previous studies, which is reflected in the local variation in the hazard maps. The design response spectra at engineering bedrock level can be computed for any location in the study region from the hazard distributions. The results will be useful for earthquake-resistant design and construction of structures in this region.