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The images of collapsed, and collapsing buildings are truly distressing.
After all, structural failure is the main reason for the catastrophic loss of life in this earthquake.
So why has it been so bad in an area of known risk?
Above all else, this was a very severe earthquake. Possibly even more severe than even Turkey’s knowledgeable and experienced seismic risk scientists had calculated in worst-case scenarios.
Evidence of this comes from the seismic sensor network in Turkey which measures the amount of ground shaking during quakes – in this case around the East Anatolian Fault which caused the disaster.
Data is preliminary, and could be revised, but some of the highest measurements from some of those sensors exceed the limits for shaking that are assumed in Turkey’s earthquake building design codes.
These typically require buildings to cope with a severity of ground shaking expected to occur once every 475 years. And resist collapsing in a once-every-2,475-year event.
But some sensors recorded peak ground accelerations – a key measure of the earthquake’s force – of well in excess of 7m per second squared.
Turkey-Syria earthquake – latest updates
These values, say experts, appear to exceed the shaking predicted to occur in these areas, even in that rarest, one-in-2,475-year earthquake event.
“Even the very well-designed, very well-executed buildings would have suffered and would have been challenged,” says Prof Yasemin Didem Aktas, a structural engineer at University College London.
“But this doesn’t rule out the building stock we are seeing collapsing was free of defects and problems,” she adds.
More news:
Woman whose family was wiped out tells Sky News: ‘I wish I’d died and my children had lived’
John Sparks: Searches for signs of life in Kahramanmaras, the Turkish city at the epicentre
Alex Crawford: Tempo of rescue operation in one of the worst-hit areas has changed dramatically
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