The North Anatolian Fault runs under the Sea of Marmara, twelve kilometres south of Istanbul's historic peninsula. It last ruptured catastrophically beneath the city in 1509. Since 1939 it has been releasing strain in a westward sequence of major earthquakes — Erzincan, Niksar, Düzce, Adapazarı — that geophysicists describe as a zipper closing toward Istanbul. The 1999 Marmara earthquake killed 17,000 people and flattened 77,000 buildings in cities fifty kilometres from the fault's most dangerous section. Istanbul escaped that one. The scientific consensus is clear: the next one will not miss.

Turkey's Urban Transformation Law — passed in 2012 and tightened after the 2019 Elazığ earthquake exposed enforcement gaps — requires seismic assessment and retrofit or demolition for all buildings constructed before the updated 1999 code. In Istanbul, that is approximately 840,000 structures. The largest compulsory urban renovation programme in the world.

The halfway milestone — 420,000 buildings assessed, retrofitted, or replaced — arrived in January, eight months ahead of the interim schedule. The acceleration came down to money. Government-backed retrofit loans at 1.2 percent annual interest, repayable over 20 years, with the obligation transferring to new owners on sale. That turned compulsory assessment from something property owners resisted into something they chose voluntarily. Smart policy design. It worked.

Engineers modelling a magnitude 7.5 scenario on the Marmara fault estimate that the completed retrofits cut building collapse rates from a projected 18 percent to below 4 percent. In a city of 15 million, that gap is the difference between catastrophe and disaster. Both words apply. Only one of them is survivable.

"We are not preventing the earthquake," said Mayor Ekrem İmamoğlu. "We are preventing the city from falling down when it arrives."

Istanbul's Earthquake Retrofit Programme Reaches Half the City's Pre-1999 Buildings Ahead of the Predicted 'Big One'