Fragile geological features (FGFs) provide a unique empirical basis for validating, calibrating, and evaluating probabilistic seismic hazard analysis (PSHA) models over pre-instrumental timescales that far exceed the duration of measured and historical earthquake records. Over such long periods, uncertainty in ground-motion intensity estimates becomes especially large, while the survival of delicate landforms offers an observational upper bound on the level of shaking experienced since they reached their current geometry. We present a comprehensive dynamic fragility analysis of the “Lot’s Wife” pillar - a slender, evaporitic rock column located at Mount Sodom near the Dead Sea, which has survived for ~ 4000 years in a seismically active region. The pillar is composed primarily of halite with an anhydrite cap and exhibits pronounced geometric asymmetry and spatially varying mechanical characteristics. To characterize its dynamic response, an integrated framework was developed combining in situ ambient-vibration measurements using Laser Doppler Vibrometer (LDV) with 3D finite-element (FE) modeling, including modal and transient dynamic analyses.
A numerical model was constructed and calibrated by comparing measured natural frequencies with modal analysis results obtained in Abaqus. The comparison revealed minor discrepancies that are likely to reflect modeling assumptions and simplifications.
Subsequently, dynamic analyses were performed using a suite of representative earthquake ground-motion records selected to span a broad range of plausible shaking intensities and source-to-site distances for the Dead Sea region. The relationships between peak ground acceleration (PGA), Arias intensity (Ia), and the development of basal tensile stresses (S22) were evaluated. The simulations enabled the definition of a dynamic fragility envelope describing combinations of seismic intensity measures that may trigger structural failure. The results indicate that scenarios characterized by the coupled effect of high ground acceleration and substantial seismic energy input (high Ia) are most likely to exceed the established fragility threshold. Given the multi-millennial persistence of Lot’s Wife, these findings provide a quantitative constraint on past ground-motion levels near the Dead Sea and suggest potential overestimation in portions of regional ground-motion predictions derived from NGA-West2-based models.