Sensitivity of the liquefaction potential index to design-scenario assumptions: Implications for seismic hazard classification of loessial soils

The liquefaction potential index (LPI) is widely used as a single-number measure for hazard classification and mapping, yet it is computed for a specific design scenario — peak ground acceleration (PGA), earthquake magnitude and groundwater position — and published values are often compared without reference to these assumptions. This paper quantifies the sensitivity of the SPT-based LPI to each scenario parameter for a saturated loessial profile in Tashkent investigated by 68 standard penetration tests. A full parametric sweep was performed over PGA 0.15–0.45 g, moment magnitude 6.0–7.5 and groundwater depth 2.0–5.5 m. The index proves hypersensitive to PGA in the moderate-shaking range, growing from 0.7 to 17.0 between 0.15 and 0.25 g and crossing all hazard categories; the magnitude assumption alone changes the index by a factor of about 1.9; and raising the water table by 1.5 m produces an increase that cannot be reproduced by any acceleration growth up to 0.6 g, because near-surface saturation activates the depth range with the greatest weight in the Iwasaki formulation. LPI values are therefore neither comparable nor mappable without explicit scenario metadata, and a scenario-matrix reporting format is proposed.

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