PSI - Issue 78

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

1901

Earthquake increased it to 6%, still following a prescriptive approach. The 1975 code introduced concepts such as column confinement and a 10% base shear for standard buildings. However, the poor material quality and construction have limited their impact. The 1998 code, following the 1992 Erzincan event, adopted capacity design principles, lateral drift limits, and irregular classifications. Refinements in 2007 and 2018 further embraced performance-based earthquake engineering (PBEE), but the latter was criticized for its complexity and limited practical adoption. Despite academic progress and institutional support, systemic challenges have persisted. The rapid expansion of engineering programs and the lack of a formal chartered engineering system have lowered professional standards. Post-1999, third-party inspections were compromised by contractor control, with more independent inspections emerging only after 2018, while inspections were mostly performed after construction, leaving a gap in quality control. Urban planning reforms began with the 1985 Planning Law No. 3194, decentralizing authority to municipalities and introducing disaster risk into legal frameworks. However, seismic considerations, such as soil effects and resonance, are often ignored. Plans commonly use road width to determine building height without geotechnical input, and mismatched adjacent floor levels increase the pounding risks. Illegal construction surged due to internal migration and economic disparity, and was tolerated politically and legalized via multiple amnesty laws from 1948 to 2018. The 2018 amnesty alone registered over 3 million buildings (ÇŞB, 2018), with an estimated 500,000 illegal modifications in the earthquake-affected region. Unauthorized floor additions and the removal of ground floor walls created soft storey mechanisms, severely reducing seismic resilience and increasing collapse risk. Seismic hazard zoning has also evolved. The 1948 map divided Turkey into three zones, misclassifying key fault areas such as Kahramanmaras. Subsequent updates in 1963 and 1972 added zones but relied mainly on historical intensity data, still underestimating risk along the East Anatolian Fault Zone (EAFZ). The 1996 map introduced probabilistic seismic hazard assessments with peak ground acceleration (PGA) values, finally recognizing the EAFZ as a high-risk Zone I. The 2019 AFAD map aligned with the 2018 TBEC provides continuous PGA data and confirms that the EAFZ and surrounding provinces are among the highest-hazard regions. This long-standing underestimation contributed significantly to the vulnerability to the 2023 Kahramanmaras Earthquakes. 4. Conclusions The Kahramanmaras earthquake sequence exposed not only structural and geotechnical weaknesses, but also deep institutional, legal, and social shortcomings in Turkey’s seismic risk mitigation. Failures, such as soft-storey mechanisms, overload collapses, and column shear failures, are familiar with past events and are well documented in earthquake engineering, highlighting a persistent gap between knowledge and practice. A major factor was the widespread legalization of unauthorized, non-engineered buildings through political measures, such as zoning amnesties. The 2018 campaign alone resulted in over three million applications nationwide, including an estimated 500,000 applications in the affected area. Many buildings had illegal additions or removed structural elements, which weakened their load capacities and seismic integrity. The severity of the disaster was compounded by two strong earthquakes striking within 9 h, a scenario not accounted for in modern codes, such as TBEC 2018. This repeated loading caused the structures to fail, emphasizing the need for scenario-based design approaches in seismic regions. Spectral accelerations at many sites exceeded the code design values. Although TBEC 2018 includes drift limits and reinforcement details, it does not require shear walls in typical mid-rise buildings. The presence of such lateral force-resisting elements could have offered a cost-effective safeguard against unexpectedly high ground motions. Historic misclassification of seismic hazards has also contributed to the widespread damage in the region. Before 1998, large parts of the Eastern Anatolian Fault Zone were considered low-risk or inactive; the Kahramanmaras region was classified as such on the 1948 map. This has led to the widespread under-design of existing buildings. Although modern maps have corrected these errors, legacy vulnerabilities still remain. These technical issues are worsened by systemic problems in terms of construction, oversight, and governance. The absence of a national chartered engineering system, weak third-party inspections, and proliferation of unregulated engineering programs have diluted professional quality. Engineers often face commercial pressure with limited enforcement power. Improving seismic resilience requires a comprehensive approach, including informed urban planning, responsible architectural and structural design, and strict supervision and enforcement. Public education, investments in early warning systems, and emergency preparedness are vital. In conclusion, the 2023 Kahramanmaras Earthquake revealed long-standing systemic failures, rather than an unforeseeable event. Political decisions, such as construction amnesties and