Turkey's earthquake is a warning for Istanbul, which would face even more deaths from a quake
City has 15 million people and thousands of buildings that aren't ready
The high death toll from the massive earthquake in southeastern Turkey and northern Syria is in large part a result of the poor structural integrity of thousands of buildings, experts say.
This is why Istanbul, a city of 15 million people which geologists predict will eventually get hit by a strong quake, could see tens of thousands of deaths unless action is taken on the thousands of buildings in the city that aren't earthquake proof or resistant.
"What we see today in [southeastern] Turkey is just a preview of what will happen in Istanbul," said, Ihsan Engin Bal, a professor of the Research Group on Earthquake Resistant Structures at the Hanze University of Applied Sciences in the Netherlands.
"I'm not saying what may happen. I say what will happen. What will happen in Istanbul is way bigger than this. Way bigger."
While efforts have been made to modernize building codes and protect against tremors, researchers say there is a vast challenge getting older buildings safe enough to withstand a quake.
Near major fault line
More than 17,000 people have been killed by the 7.8-magnitude tremor that hit earlier this week about 26 km east of the Turkish city of Nurdagi at a depth of about 18 km on the East Anatolian Fault.
Turkey lies on two major fault systems, the North Anatolian Fault and East Anatolian Fault, making it the country in that area with the highest risk to be affected by a quake. Earthquake researchers predict that an earthquake of magnitude 7.0 or stronger is very likely to strike Istanbul, which is close to the North Anatolian Fault, within the next 70 years.
"If that that happens, we're talking hundreds of thousands [of fatalities] potentially because of the population of Istanbul. And those buildings are not ready," said Joanna Faure Walker, a professor of earthquake geology and disaster risk reduction at University College London's Institute for Risk & Disaster Reduction.
"That is definitely somewhere where the [geological] community is worried about because the earthquakes are progressing along that fault and because the buildings in Istanbul are not designed to be seismic resistant."
Estimates vary as to potential losses of life if an earthquake struck Istanbul. The municipality of Istanbul conducted its own study estimating that 14,500 people will die if a magnitude 7.5 earthquake happens at night. One study by a group of European researchers projected 30,000 to 40,000 would be killed.
But Bal believes those estimates are low, with his own study estimating 47,000 buildings would be destroyed, with the possibility of 150,000 people killed.
Appear to be extremely vulnerable
The problems in Istanbul are the same problems that have come to light in this most recent earthquake — many of the buildings in Turkey appear to be extremely vulnerable.
Just from her initial observations of the damage, Faure Walker said the destroyed buildings she sees in pictures and video seem to lack basic earthquake-resistant structures, like reinforced concrete or column bracing.
Another problem, she said, is the issue of "pancaking," where essentially the inside of the building collapses, a sign that the internal floors and structures aren't connected strongly enough to the outer wall.
"If it's in the middle of a night, it's very hard for people to escape because when a building collapses in that way, there's very little gaps, so essentially someone is crushed."
Jerome Hajjar, a professor and department chair of the department of civil and environmental engineering at Northeastern University in Boston said it's likely that a good number of the structures may have only lightly reinforced concrete or masonry.
"And those types of structures are known to have vulnerabilities for major earthquakes," he said.
Many homes in Turkey were built in the 1970s, '80s and '90s, before international standards for earthquake-proof buildings were established, Bal said.
Not clear if new rules are working
But the magnitude 7.4 earthquake that struck the western city of Izmit in 1999, killing more than 17,000 people, led to a new set of regulations and a stricter seismic code in Turkey, he said.
"After the year 2000 I can't claim that it was still ideal, but it was way, way better than before," Bal said.
However, he said that from viewing videos and pictures from the recent earthquakes, "buildings that were built, just a year ago or less also collapsed. That is not supposed to happen"
"If those buildings were built according to the most recent seismic regulations, even under these large earthquakes, they are supposed receive some severe damage, but still stand, not collapse.
"So that was surprising to me. Which tells me that in that region, or maybe in all Turkey, those regulations and controls are loosened again."
Walker said an investigation certainly needs to be conducted to see how many modern buildings were destroyed.
"Is it that the codes aren't strict enough or is it the people aren't complying with the codes? And if they're not complying with the codes, is that because lack of enforcement, is it because of lack of funds?"
Still, according to Bal, the majority of buildings that collapsed in this earthquake were ones built before the 2000 regulations came. So what can be done with those structures?
Retrofitting those buildings to meet the seismic codes is certainly a possibility. But there are thousands of those buildings; it would be incredibly costly and many of those buildings are generally in poor shape, Bal said.
"And it just doesn't make sense to to spend huge amounts of money to retrofit such an awful quality building."
Instead, there need to be some incentives to get people to rebuild or move somewhere into safer structures, he said.
"The number of buildings in that category is huge. Resources in terms of time, people and money will not be enough to do it in a short time. Plus, it requires very good planning and incentives that can run for several decades," Bal said.
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With files from Reuters