Probabilistic Seismic Hazard Assessment (PSHA) of Gilgit-Baltistan

Abstract

This research performs a Probabilistic Seismic Hazard Assessment (PSHA) for Gilgit Baltistan, utilizing US National Seismic Hazard Mapping project methodologies. This study uses smoothed seismicity to determine and quantify the risk of seismic activity within the region. According to the Global Earthquake Model (GEM) database, 42 crustal faults are identified in the study area, out of which 30 faults are active and have been modeled in 3D. PSHA uses a logic tree technique to addressing epistemological uncertainties related to characterization of sources and Ground Motion Attenuation Relationships (GMARs). Seismic Hazard Maps have been developed for the PGA and SA at 0.2 seconds (Ss) and 1.0 seconds (S1). These maps represent Design Basis Earthquake (DBE) level, which has a 10% probability of exceedance (PE) in 50 years, and Maximum Considered Earthquake (MCE) level, which has a 2% probability of exceedance (PE) in 50 years. Seismic Hazard in Gilgit-Baltistan regarding PGA varies between 0.10 g to 1.10 g for DBE level and from 0.30 g to 2.20 g for MCE level. For spectral acceleration at 0.2 seconds (Ss), the hazard values for DBE level range from 0.30 g to 2.10 g, while for MCE level, it ranges from 0.70 g to 4.20 g. Alternatively, for the spectral acceleration at 1.0 seconds (S1), the hazard values range from 0.10 g to 0.60 g for DBE level and from 0.30 g to 1.30 for MCE level. Furthermore, a Uniform Hazard Spectrum has also been prepared for Gilgit City. This research provides a thorough assessment of seismic hazards for Gilgit-Baltistan region and might benefit decision-makers who are interested in reducing seismic risks.