Soil Characterization and Liquefaction Potential Mapping in Nepal’s Terai Region

Nepal, identified as one of the world's most disaster-prone areas, has a history of frequent earthquakes. Despite its seismic activity and vulnerability to liquefaction, the Terai region lacks comprehensive studies on site characterization and liquefaction potential. This research focuses on evaluating the liquefaction potential of the Terai region's soil, crucial due to its high population density and the imperative to ensure the safety of engineering structures. In this study, in-situ parameters are utilized to assess the subsurface geology's liquefaction potential, encompassing soil characterization, soil liquefaction factor of safety (FS), and liquefaction potential index (LPI). Data from 284 boreholes, collected at 97 locations within the study area up to a depth of 20 m, offer insights into the Terai region's seismic vulnerability. Considering an earthquake scenario with a magnitude (Mw) of 7.8, liquefaction resistance was assessed at each location using peak ground acceleration (PGA) varying from 0.3 to 0.4 g as specified in NBC 105 (2020) for each district. The results indicate the LPI range of 0–57.85, with 34.02% of the Terai region classified as very high risk, 15.46% as high risk, 23.72% as low risk, and 26.80% as very low risk or liquefaction hazard. A hazard map is generated based on liquefaction potential, offering valuable insights for planning, management, and long-term development in the studied locations. This research addresses the crucial knowledge gap in understanding the seismic vulnerability of the Terai region, providing a basis for informed decision-making and risk mitigation strategies.