Seismic Settlement Analysis of Nihal Atakaş Mosque: A Comparison of Field Observations, Empirical and Semi-Empirical Estimates, and 3D Seismic Soil-Structure Interaction Simulation Results

This study compares seismic-induced settlements measured adjacent to the Nihal Atakaş Mosque following the 2023 Türkiye Earthquake Sequence against estimates from several methods of varying sophistication. Located on the coast of İskenderun, the mosque was built on reclaimed land supported by a deep foundation and underwent only minor damage during the earthquakes. However, near-field areas surrounding the mosque experienced settlements up to 300 mm. The presence of surface ejecta around the structure confirmed the occurrence of liquefaction. This paper discusses three approaches used to estimate seismic settlements excluding ejecta-induced settlements: (1) post-shaking reconsolidation settlements using (a) conventional empirical relations and (b) a combination of empirical relations and undrained, bi-directional soil column dynamic finite element simulations; (2) direct computation of free-field settlements from partially drained, bi-directional soil column simulations; and (3) 3D seismic soil-structure interaction (SSI) analysis of the entire system under bi-directional shaking and partially drained conditions. The ejecta-induced settlement, unaccounted for in all these approaches, is then calculated and added on. The results demonstrate that conventional empirical procedures may overestimate post-shaking reconsolidation settlements, while free-field numerical simulations can capture only part of the mechanisms. 3D SSI simulations, on the other hand, when combined with ejecta estimates, closely reproduced the measured 230–300 mm settlements. In addition, 3D SSI modeling with explicit ejecta consideration provides mechanistically consistent and physically distinguishable settlement estimates.