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Unreinforced structures pushed up Iran death toll


LACK OF structural reinforcement was a major contributor to the heavy death toll caused by the Boxing Day earthquake in the Iranian city of Bam, engineers report.

The 6.6 Richter scale event devastated hundreds of buildings when it struck in the early hours. The death toll is estimated at close to 40,000.

A team of American based Iranian engineers put together by the US Earthquake Engineering Research Institute (EERI) flew out to Bam in January. It has already drawn some conclusions about the quake's impact.

'Some 90% of the city's structures were built primarily from unreinforced mud brick masonry and adobe, ' Californian structural engineer and team leader Tarzad Naeim told NCEI.

'Much of this collapsed. But any building with almost any small amount of lateral resistance of whatever form, stayed up, even if it was damaged.'

Among the surviving buildings are factories on a small industrial estate.

Coincidental occurrence of a similar earthquake at San Simeon, California, just four days before the Iran disaster reinforced the lessons learned in Bam, said Professor Tom O'Rourke from New York's Cornell University and president of EERI.

'San Simeon was almost identical seismically with a magnitude of 6.5 and an 8km focal depth, ' he said.

'But the damage was much less, with two fatalities and around 40 buildings severely damaged or collapsed.'

Nearly all the damage in California was in older, unsupported, unreinforced masonry structures, he added.

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