Turkey’s most crowded city Istanbul could be hit by the "big one," a major earthquake predicted to strike in an uncertain future.

Projections show 491,000 buildings out of about 1.2 million buildings in the city of more than 15.8 million people will be damaged in a potentially severe earthquake. According to projections, more than 13,000 will sustain the heaviest damage and probably collapse, while more than 39,000 others will suffer from heavy damage. Experts warn that the disaster may be more severe without retrofitting the buildings against earthquakes or rebuilding them from scratch with sturdy material.

Based on the average number of 12 residents per building, some 6.2 million people live in those places that may sustain damage.

The city last experienced a major earthquake in 2019, when a 5.8 magnitude tremor shook its European side. Casualties were limited to one while several buildings suffered from minor damages. But it was a stark reminder of a 1999 earthquake that killed hundreds in the city’s Avcılar district.

Speaking on the occasion of Earthquake Week, marked between March 1-7 and to raise awareness of the issue, Sinan Türkkan, head of Earthquake Fortification Association (DEGÜDER), said more people are interested in reinforcing their buildings nowadays. Türkkan told Anadolu Agency (AA) on Tuesday that earthquakes in the past two years and the COVID-19 pandemic fuelled the demand. "The longer people had to stay at home because of curfews and quarantines, the more they became aware of risks," he said. Another factor in rising interest is increasing construction costs, according to Türkkan. "There is a cost advantage by 60% in reinforcing a building instead of constructing a new one. It also takes a shorter time," he added.

He said 90% of the buildings susceptible to damage in a potential earthquake can be "saved" by reinforcing it. "A severe earthquake is awaited in the future. We call upon citizens to test the endurability of their buildings as soon as possible and if it has the potential for damage, to reinforce it," he highlighted.

"We cannot replace all buildings with new, sturdy ones and it is not necessary anyway. But with low cost and in a shorter time, we can reinforce them. If it is not possible, we have to transform them," he said. The government already pursues an ambitious "urban transformation" project across the country, prioritizing the provinces under earthquake risk. It involves the demolition of buildings and reconstruction on the site or elsewhere with the government’s incentives.

Professor Gürsel Öngören, who heads Urban Transformation and Law Platform, a nongovernmental organization (NGO), said it has been 10 years since an urban transformation law was enacted but not all the buildings unsafe against earthquakes were transformed. "The law stipulates that unsafe buildings should be evacuated within 60 days of notice. We have to mobilize and the municipalities should accelerate the process of identifying unsafe buildings," he told AA.

Öngören said citizens also should not await evacuation notices and contact the relevant government agencies for reinforcement or transformation of their buildings, citing incentives provided by the Ministry of Environment, Urban Planning and Climate Change.

The ministry had launched a new building inspection system in 2011 to thoroughly examine buildings' safety in case of a disaster. Since then, millions of "independent units" from flats to workplaces and some 868,000 buildings have been inspected. Currently, 488,000 buildings across the country are being inspected by the ministry in cooperation with private building inspection companies.