PSI - Issue 78

Yavuz Yadim et al. / Procedia Structural Integrity 78 (2026) 1895–1902

1897

critical slip deficit and supporting a slip prediction model. Liu et al. (2025) provided detailed surface rupture mapping and evidence of extensive off-fault damage, emphasizing the complex rupture behavior of this event. These studies collectively confirmed the tectonic and structural susceptibility of the region to large-magnitude earthquakes. Earlier work by Armijo et al. (1999) highlighted the neotectonic activity of the EAFZ and its role in accommodating motion between the Anatolian and Arabian plates. More recently, Provost et al. (2024) used satellite imagery to map co seismic surface ruptures and revealed highly variable fault displacements and segmentations. Ground motion analyses of the 2023 Kahramanmaras earthquakes showed that peak ground accelerations (PGA) significantly exceeded the Turkish Building Earthquake Code (TBEC, 2018) predictions, particularly for short-period structures. The recorded horizontal PGAs exceeded 1000 cm/s ² in Antakya and 1600 cm/s² in parts of Kahramanmaras and Gaziantep, including Elbistan, Türkoğlu, and İslahiye. In several cases, ground motions exceeded both the Design Earthquake and Maximum Considered Earthquake levels (Erdik et al., 2023; Gülkan & Akansel, 2024). These extreme conditions challenge the adequacy of current seismic design provisions and emphasize the need to revise hazard models and design approaches, particularly near active fault zones. Despite the dominance of RC construction in Turkey and Syria, the consistent application of seismic-resistant designs remains limited, particularly in older or informally built structures. The 2023 earthquakes exposed recurring vulnerabilities, including inadequate shear reinforcement, poorly detailed beam-column joints, and low-strength concrete. Corrosion of the reinforcement is often worsened by insufficient concrete cover, and poor construction practices further weaken the structural integrity. Additional risks arose from cantilevered balconies modified by occupants and soft-storey configurations, especially in ground-level commercial spaces where columns were removed or under-reinforced, creating stiffness discontinuities. Architectural irregularities and abrupt changes in mass and stiffness further amplified localized damage and collapse risks. In Syria, building conditions were even more fragile. Years of conflict and economic hardship severely curtailed new construction and maintenance. Essential preservation measures, such as repairing concrete covers and cracks or applying protective coatings, were largely absent, accelerating the structural degradation and reducing the seismic resilience. 2. Damages to civil structures Liquefaction, a well-known phenomenon in loose saturated soils below the water table, was observed in multiple areas during the February 6, 2023, earthquake (Tobita et al., 2024). Strong shaking increases the pore water pressure, reduces the shear strength, and causes soil instability. As described by Boulanger and Idriss (2014), this can lead to severe settlement, tilting, or overturning of the structures, as illustrated in Fig. 2. Since the 1999 Marmara Earthquake, raft foundations have become common in Turkey, favoring simplicity and perceived safety. However, many lack proper geotechnical evaluation, and insufficient liquefaction mitigation has left buildings vulnerable, particularly in areas with loose, saturated soils. Recent earthquakes highlight the urgent need for detailed site-specific soil investigations and improved foundation designs that incorporate liquefaction countermeasures. Several design-related deficiencies have contributed to widespread structural failures during the February 2023 earthquakes. The key among them are architectural irregularities, poor detailing, and inadequate provisions for seismic interaction in densely built areas (Avğın et al., 2024). A particularly critical issue was the pounding effect caused by insufficient separation between adjacent buildings, which is a common feature in Turkish cities. Under seismic loading, out-of-phase vibrations led to slabs or walls impacting neighboring structures, amplifying stress and triggering localized failures or progressive collapse. Turkey’s urban housing stock, dominated by multi-storey RC apartment blocks, expanded rapidly during periods of rural-to-urban migration. To meet housing demands, compact urban plans allow block-type buildings on small subdivided plots, often with minimal spacing between the structures. Pounding effects are particularly severe when adjacent buildings differ in floor levels or total height, resulting in impacts that significantly increase stress concentrations and damage. While many heavily damaged or collapsed buildings were older, a significant number were relatively recent and supposedly built into the modern seismic standards. This highlights that the problem lies not with the Turkish Earthquake Codes themselves; both the 1975 and 2018 versions provided adequate seismic provisions, but with weak enforcement, limited construction oversight, and systemic accountability failures. The vulnerability of the existing building stock was further amplified by government policies, notably the Construction Amnesty, which legalized unauthorized and noncompliant buildings. Many of these structures lacked