A seismic task: Istanbul awaits a once-in-a-century earthquake

In this metropolis of 15 million inhabitants there’s a terrifying event that few people talk about, but everyone accepts one day, perhaps decades from now, will eventually come to pass. A major earthquake could cause up to 30,000 deaths, level 44,000 buildings and leave 2.4 million people homeless overnight.

“Our scenario suggests that an earthquake with a magnitude of 7.6 on the Northern Anatolian Fault in the Marmara Sea could kill 26,000 to 30,000 people,” Murat Nurlu of Turkey’s Disaster and Emergency Management Authority (AFAD) told a workshop in Istanbul on August 15th.

On August 17th, Turkey commemorated the 19th anniversary of the 1999 Izmit earthquake that killed 17,500 people, an event widely regarded as the "disaster of the century". The anniversary serves as a reminder that, according to countless studies, the worst is yet to come for Istanbul.

Turkey’s largest city sits on the North Anatolian Fault, one of the most active seismic zones in the world. With the last major quake recorded here in 1894 and the city historically experiencing one every 100 years, scientists say the next strike may not be far off.

British-Iranian aid worker temporarily released from jail

---

Australia’s PM fights to the end but his time appears up

---

Brexit: UK to seek deal on North-South trade in case of no-deal Brexit

---

The 7.6 magnitude Izmit earthquake that struck 70 kilometres east of Istanbul 19 years ago still lingers in the thoughts of Mustafa Erdik, the president of the Turkish Earthquake Foundation. Research Erdik and his colleagues have conducted in the years since point to a 33 per cent chance of a major earthquake striking Istanbul in the next 15 years. “Istanbul is one of the best-studied areas in the world but no one can predict when it will happen. So there’s a race to mitigate the damage,” he says.

At-risk residential units

Swiss Re, a reinsurance company, says 6.4 million residents would be "endangered" by an earthquake – far more than in any natural disaster anywhere else in Europe. The number of at-risk residential units stands at between 200,000 and 250,000, according to Turkey's minister for urbanisation and environment. Added to that is the threat of a subsequent tsunami from the Marmara Sea south of Istanbul that could lead to waves one to two metres high descending on the city 30 minutes to an hour after the quake.

Istanbul is Turkey’s financial and economic heart and contributes around 40 per cent to the country’s GDP, meaning a major quake would result in serious long-term economic consequences. Many of its thousand-year-old cultural heritage sites and monuments would likely be damaged or destroyed. Outside of the metropolitan area, the Marmara region that runs along the fault line is home to a further six million people and serves as the country’s manufacturing heartbeat. Turkey’s most important ports and oil and gas facilities are located east of Istanbul and suffered significant damage during the 1999 quake.

The problem with earthquakes, of course, is the almost total inability to predict when they will occur. Istanbul’s high probability of suffering a quake, combined with the devastation wrought in Izmit in 1999, has motivated urban planners and city authorities to act now in preparation for the worst. Many efforts to lessen the effects of an earthquake – the slip-strike variety facing Istanbul – have been carried out over the past two decades.

Over 700 public buildings were retrofitted, while food reserves put together by the Istanbul municipality can feed 250,000 people a day. In March, Turkey updated its building code for the first time in over a decade, and compulsory earthquake insurance for residential and work properties has been introduced.

Urban train line

The 1.4-kilometre-long section of the Marmaray urban train line that runs under the Bosphorus Strait has been built to withstand a magnitude 7.5 quake. The third Bosphorus bridge, which opened in 2016, has also been constructed to lessen the effects of serious seismic activity. Schools and hospitals used by 1.1 million students and 8.7 million patients respectively have been retrofitted.

The ability to operate a major transportation node, like an airport, after an earthquake has many benefits

These efforts combined have resulted in the World Bank citing Istanbul as one of the world’s most proactive in earthquake risk mitigation.

In the fallout of a major earthquake, infrastructure that helps keep access with the outside world open during the recovery stage takes on greater importance. That’s partly why the Sabiha Gökcen airport on the eastern edge of Istanbul was reconstructed in 2009 as the world’s largest earthquake-resistant building.

“The ability to operate a major transportation node, like an airport, after an earthquake has many benefits including receiving humanitarian aid, aiding in the process of returning to normal activities and contributing to the city/community resiliency,” says Atila Zekioglu, the project seismic expert for engineering firm Arup during the airport build. The terminal sits on a “friction pendulum seismic-isolation system” that protects it from major movements of the ground underneath.

Although efforts such as these are sure to help save lives, there are limits. While having an airport terminal open and operating in the aftermath of a major earthquake is hugely helpful, it functions only if the runway it serves is unscathed.

Building stock

Istanbul is a city of 1.5 million buildings, meaning that retrofitting several hundred is but a drop in the ocean. A third of the city’s building stock was built in the 1960s and 1970s, say experts, meaning a huge number don’t meet modern building codes. The food supplies currently stored by municipal authorities would feed only a fraction of the city’s population.

And while government figures have been at pains to point out that the recently built bridges and subterranean tunnels can withstand a 7.5 magnitude quake, as last week’s workshop illustrates, state-employed specialists are openly warning of a far stronger seismic event (a 7.6 magnitude earthquake packs 140 per cent the energy of a 7.5).

All the while, some critics suggest government officials are exaggerating the threat to push through hugely profitable regeneration projects.

“The quality of some [modern-built] high-rises are questionable – not all, of course,” says Erdik. “But what is more important is how close to the seismic fault you are, not so much that the foundations of buildings are an issue.”

With Istanbul’s population set to rise by five million over the coming 20 years, the fallout could be even greater than previously imagined.