Liquefaction Screening Checklist (NCEER/NSF Format)

The NCEER/NSF Liquefaction Screening Checklist was formalized in the 1990s as part of broader efforts to standardize seismic risk assessment practices following lessons learned from major earthquakes such as the 1989 Loma Prieta and 1994 Northridge events. It operates on a tiered screening philosophy: Tier 1 uses readily available information (e.g., surface geology, historical liquefaction reports, topographic setting) to eliminate low-risk sites; Tier 2 incorporates limited subsurface data (e.g., Standard Penetration Test (SPT) N-values, CPT tip resistance, groundwater depth) to estimate cyclic stress ratio (CSR) and cyclic resistance ratio (CRR); and Tier 3 recommends advanced analyses (e.g., simplified stress-based methods, numerical modeling) when screening indicates significant potential. The checklist emphasizes conservative assumptions and clear pass/fail thresholds based on empirical correlations calibrated against case histories—particularly those compiled in the NCEER Liquefaction Database. Its strength lies in its accessibility to practicing engineers without requiring extensive computational resources or deep geotechnical modeling expertise, while still maintaining traceability to fundamental soil mechanics principles including effective stress, pore pressure generation, and shear strength degradation. Importantly, it explicitly acknowledges limitations—such as applicability only to cohesionless soils (primarily sands and silty sands), exclusion of sensitive clays or highly plastic silts, and reduced reliability in regions with sparse local calibration data.