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<p>Soil liquefaction and ensuing ground failure significantly contribute to structural damage in loose, non-cohesive, and water-saturated alluvial regions during moderate-to-great earthquakes. The Bengal Basin, situated on the Ganga-Brahmaputra-Meghna Deltaic deposits, exhibits a subsurface lithological sequence comprising silt, clay, sand, and gravel. Notable earthquakes, namely 1885 Bengal (M<sub>W</sub> 6.8), 1918 Srimangal (M<sub>W</sub> 7.6), 1897 Shillong (M<sub>W</sub> 8.1), 1934 Nepal-Bihar (M<sub>W</sub> 8.1) etc. reportedly triggered sporadic liquefaction in the region, thus forming the basis for systematic liquefaction potential modelling. In this study, synthesised bedrock ground motion using finite-fault stochastic simulation has been accompanied by 2-D site response analysis to estimate site amplification and surface-compliant Peak Ground Acceleration (PGA). Factor of Safety (FOS), Liquefaction Potential &amp; Risk Indices (LPI &amp; I<sub>R</sub>), Probabilities of Liquefaction (P<sub>L</sub>) &amp; Ground Failure (P<sub>G</sub>) have been estimated to understand the severity of liquefaction, considering eight historical earthquakes. The predicted LPI distribution associated with surface-compliant PGA for 475-years return period varying in the range of 0.09–1.40&#xa0;g has demarcated the Basin in four categories as ‘low (LPI = 0)’ in Bhubaneswar, ‘moderate (0 &lt; LPI ≤ 5)’ in Dhanbad ‘high (5 &lt; LPI ≤ 15)’ in Rajshahi, and Kolkata, and ‘severe (LPI &gt; 15)’ in Dhaka, Sylhet, Mymensingh and Chittagong, while, the I<sub>R</sub> map divided the region into ‘Low (I<sub>R</sub> ≤20)’, ‘High (20 &lt; I<sub>R</sub>≤30)’ and ‘Extremely High (I<sub>R</sub>&gt;30)’ classes. Through back analysis, target SPT-N values (<i>N</i><sub><i>improved</i></sub>) in potentially liquefiable zones have been calculated to ensure no liquefaction during probabilistic scenarios. This estimate of liquefaction potential and associated risks is believed to catalyze efforts in reducing structural vulnerability by enhancing soil/sediment strength and stiffness.</p>

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Probabilistic seismic hazard and historical scenario-based assessment of liquefaction potential in the Bengal Basin for liquefaction mitigation strategies

  • 期刊论文

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  • 发表日期：

    2026年8月5日

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  • Arpita Biswas,
  • Sankar Kumar Nath

摘要

Soil liquefaction and ensuing ground failure significantly contribute to structural damage in loose, non-cohesive, and water-saturated alluvial regions during moderate-to-great earthquakes. The Bengal Basin, situated on the Ganga-Brahmaputra-Meghna Deltaic deposits, exhibits a subsurface lithological sequence comprising silt, clay, sand, and gravel. Notable earthquakes, namely 1885 Bengal (MW 6.8), 1918 Srimangal (MW 7.6), 1897 Shillong (MW 8.1), 1934 Nepal-Bihar (MW 8.1) etc. reportedly triggered sporadic liquefaction in the region, thus forming the basis for systematic liquefaction potential modelling. In this study, synthesised bedrock ground motion using finite-fault stochastic simulation has been accompanied by 2-D site response analysis to estimate site amplification and surface-compliant Peak Ground Acceleration (PGA). Factor of Safety (FOS), Liquefaction Potential & Risk Indices (LPI & IR), Probabilities of Liquefaction (PL) & Ground Failure (PG) have been estimated to understand the severity of liquefaction, considering eight historical earthquakes. The predicted LPI distribution associated with surface-compliant PGA for 475-years return period varying in the range of 0.09–1.40 g has demarcated the Basin in four categories as ‘low (LPI = 0)’ in Bhubaneswar, ‘moderate (0 < LPI ≤ 5)’ in Dhanbad ‘high (5 < LPI ≤ 15)’ in Rajshahi, and Kolkata, and ‘severe (LPI > 15)’ in Dhaka, Sylhet, Mymensingh and Chittagong, while, the IR map divided the region into ‘Low (IR ≤20)’, ‘High (20 < IR≤30)’ and ‘Extremely High (IR>30)’ classes. Through back analysis, target SPT-N values (Nimproved) in potentially liquefiable zones have been calculated to ensure no liquefaction during probabilistic scenarios. This estimate of liquefaction potential and associated risks is believed to catalyze efforts in reducing structural vulnerability by enhancing soil/sediment strength and stiffness.