Strong Shaking, Weak Prediction: Design-Spectrum Exceedance and Building Damage in the 2023 Kahramanmaraş Earthquakes

The 6 February 2023 Kahramanmaraş earthquake sequence produced ground motions that locally exceeded the elastic design demands of the Turkish Building Earthquake Code (TBEC-2018), yet the spatial distribution of building damage did not consistently follow the magnitude of this exceedance. This study evaluates that discrepancy using two complementary analytical layers. Layer 1 uses district-aggregated PGA across 94 districts; Layer 2 uses station-specific DD-2 design parameters mapped to 37 districts. First, observed peak ground acceleration (PGA) was compared with district-level damage across 94 districts, yielding a weak but significant relationship (Pearson r = 0.243, p = 0.018), explaining under 6% of the variance in damage ratio (R2 ≈ 0.06). Second, a stratified dataset of 59 strong-motion stations representing 37 districts was used to calculate the ratio of recorded PGA to the site-specific DD-2 design PGA. After incorporating available Mw 7.6 Elbistan/Ekinözü records into event envelope values, the exceedance–damage relationship remained non-significant (Pearson r = 0.084, p = 0.62; Spearman ρ = 0.103, p = 0.54). Five non-mutually-exclusive, qualitatively evaluated mechanisms may jointly account for this result: spatial resolution mismatch, the gap between elastic demand and actual structural capacity, site-specific soil response, near-fault pulse effects, and geotechnical hazards such as liquefaction. The findings show that PGA-based code exceedance alone is insufficient for explaining post-earthquake building damage, and should be interpreted together with structural vulnerability and local site conditions.