Istanbul could face another mass casualty earthquake soon, experts have warned. With a densely packed population of 15 million, the Turkish city is packed with houses built on slopes, some of which reach six or seven storeys high.
Geological Threat
Istanbul is also split by the Bosporus Strait, the entrance to which is just a few miles from the North Anatolian Fault, which runs across northern Turkey parallel to the Black Sea, under the Sea of Marmara, and across the Gallipoli Peninsula.
Research published in 2025 said the fault line beneath the Sea of Marmara, just south of Istanbul, is capable of a magnitude 7 earthquake, similar to the recent one in Colombia that killed at least 287 people.
Expert Warnings
Historian Owen Matthews warned that Istanbul, which is currently hit by a major quake only once every 250 years, is now an "earthquake death-trap". He wrote in The Telegraph: "Like London, it’s full of tall, thin, brick-built terraces – except that in Istanbul the houses are all built to different plans and perch precariously above one another on steep, concentric streets."
"Then there’s the unique nature of the North Anatolian fault, which historically has not shifted in single, catastrophic quakes but rather in a series of lesser jolts."
Probability and Preparedness
A study by the GFZ Helmholtz Centre in 2025 also found a 35% to 47% chance of a major earthquake hitting the city in the next 30 years.
Turkish geologist Naci Gorur also warned of the significant threat, adding: "Building earthquake-resistant cities is not a choice but a necessity for survival." He told Turkish news outlet Nefes: "We should not be talking about when an earthquake will happen. We should be talking about how people will survive."
Last month, health ministers gathered in Istanbul to discuss protections for healthcare systems in preparation for another quake.
Recent Seismic Activity
On April 23, 2025, a 6.2 earthquake struck the Sea of Marmara, resulting in one person dying from a heart attack and injuring 359 others. The shaking lasted 13 seconds, making it the most powerful earthquake to hit Turkey since the 2023 Turkey–Syria earthquakes, which killed over 55,000 people. It was also the largest to strike the North Anatolian Fault since the 1999 Düzce earthquake, and the most powerful in the Sea of Marmara region since the 1999 İzmit earthquake.
