Life on the powder keg
Earthquake in Istanbul is “overdue”
According to experts, the next major earthquake in Istanbul is overdue. photo
© Francisco Seco/AP/dpa
Earthquakes can cause excruciating suffering in a matter of seconds. Istanbul is one of the most endangered regions in the world. Despite numerous warnings, there is still no safe construction there, says an expert.
The thousands of dead after the tremors in south-east Turkey and Syria are a terrible warning for Istanbul. “An earthquake there with a magnitude of up to 7.4 is overdue,” says Marco Bohnhoff from the German Research Center for Geosciences (GFZ) Potsdam.
According to official figures, 16 million people live in the megacity, according to unofficial estimates even 20 million. There are around 1.6 million old buildings that are not earthquake-proof, explains Nusret Suna from the Istanbul Chamber of Civil Engineers. “That’s an incredibly high number.”
Next big earthquake is overdue
Turkey is located in one of the most seismically active regions in the world. A quake would also come as no surprise in the Istanbul region – the most densely populated area in the country. Although the situation in Istanbul has not changed as a result of the tremors in the south-east, the risk for the metropolis is generally as high as in the region currently affected, explains GFZ expert Bohnhoff. The mean return period for a major earthquake in Istanbul is 250 years. The last major earthquake took place in 1766 – so the next one is overdue.
The region is part of the North Anatolian Fault System, a large tectonic plate boundary known for destructive earthquakes with many victims, according to the GFZ. The main branch of the fault runs just 20 kilometers south of Istanbul below the Sea of Marmara, says Bohnhoff. “So a big earthquake would have devastating effects.”
In the past few decades, the tremors along the plate boundary have been moving more and more towards Istanbul. The closest hit so far was the earthquake near the city of Izmit, 80 kilometers away, in 1999, which killed more than 17,000 people. “The area below the Sea of Marmara is the only area of the entire North Anatolian plate boundary that has not been activated for more than 250 years,” says Bohnhoff. There are many indications that this area has been stuck for a long time and that great tension has built up.
City built on soft ground
In addition, the city is based on unfavorable ground: Unfortunately, the south-western part does not lie on solid ground like granite, but on a dried-up lagoon, explains Bohnhoff. “On soft ground there can be strong amplification of ground movements, sometimes together with liquefaction effects.” Both cause worse damage. The international airport is located in this area, so it could be difficult for rescue workers to fly in after an earthquake.
All of these risks and effects are also known in Turkey – so far, however, terribly little has been done to prevent them, as Nusret Suna from the Chamber of Civil Engineers says. “The theory has not been put into practice.” Suna criticizes that the authorities have failed to renovate old houses to make them earthquake-proof. And even buildings that were built after 1999 are often not safe, despite the corresponding regulations introduced afterwards. Architects, construction companies and other responsible persons often ignored “ethical principles and moral values” and acted driven by greed for profit. Correspondingly catastrophic consequences are to be expected for Istanbul.
The city cannot rely on early alarm via early warning systems. “An earthquake early warning for Istanbul is extremely difficult due to the small distance to the plate boundary,” explains Bohnhoff. “In the best case, the warning time is only a few seconds.”
The only way is to make the city’s buildings earthquake-proof as quickly as possible, says Suna. “If we start tomorrow, we can still save lives.” Because even if the time and strength cannot be precisely predicted: According to GFZ expert Bohnhoff, the great quake in Istanbul will definitely come. It’s only a matter of time.