A Unified Evaluation of Liquefaction Triggering via Effective-Stress Site Response Analysis and Seismic Hazard: A Case Study from the 2023 Türkiye Earthquakes

Liquefaction-induced hazard at the Saadet Yusuf Mıstıkoğlu (SYM) school in Antakya (Hatay) during the 6 February 2023 Türkiye earthquakes provide an unique case study to evaluate (i) liquefaction triggering through pore-water-pressure (PWP) generation in one-dimensional (1D) effective-stress nonlinear (NL) site response analysis (SRA), which advances beyond standard 1D total-stress assessments, and (ii) site-specific seismic hazard using an event-based deterministic seismic hazard analysis (DSHA) including near-fault effects. The SYM site is underlain by a very soft and deep soil column, with reference V _S condition of 760 m/s reached at ~ 560 m. Strong-motion records from the closest rock/rock-like stations were deconvolved to the half-space horizon beneath the site and used as input to 1D equivalent-linear (EL) and NL SRA. EL simulations produced unrealistically high pseudo-spectral accelerations (PSA) near the fundamental period due to large strains, confirming the need for NL modeling. NL results indicate that Turkish Building Earthquake Code (TBEC, 2019) DD-1 (2% probability of exceedance) and DD-2 (10% probability of exceedance) spectra cover NL spectra for periods ≲ 1.0 s, whereas for periods ≳ 1.5 s the computed PSA values from NL approach or slightly surpass DD-1; the event-based DSHA better captures this long-period amplification. Effective-stress analyses yield PWP-ratio (r _u ) ≈ 1.0 in the deeper sand layer, consistent with liquefaction observations, while the shallower sand layer remains below r _u = 1.0 because energy dissipation at depth reduces cyclic demand above. The study links observed field performance to a reproducible workflow combining PWP-based 1D analysis with DSHA for deep soft sites.