Bahram Akasheh, professor of geophysics at Tehran University and a government adviser, said a quake as strong as the one that flattened the southeastern city of Bam could kill many times more than the 30,000 people who were feared dead there.
"The building codes are almost universally ignored in Iran and Tehran is especially vulnerable to quakes because there is a major fault line running across it," Akasheh told reporters.
"The ground conditions in parts of Tehran are unfavourable: too soft, too brittle and too dangerous to build on if rules are ignored."
At least 30,000 people are
believed to have died in Bam
Northern Tehran is sitting on a major fault about 75km long and about 100 smaller fractures, Akasheh said.
He and other researchers estimate that a repeat of the last big quake to hit Tehran, which killed 45,000 in 1830,
would today kill 6% of the capital's population.
"The destruction to Tehran would be immense. About 80% of the buildings would be damaged or destroyed. Tehran is not ready for a big one."
In studies prepared for President Muhammad Khatami and his predecessor Akbar Hashemi Rafsanjani, Akasheh recommended moving the sprawling capital to a safer region further south. Tehran would still not be safe from a big tremor.
"Mr Khatami asked me to work on the issue and I recommended moving the capital. But apparently it is not possible. Pakistan and Brazil were able to do it. Why not here?"
He has said there is daily seismic activity in Tehran and on average three to four identifiable tremors of up to three on
the Richter scale every day. But there have only been two quakes as high as 4.5 in the last 100 years.
"I've forecast that there is the potential for an earthquake of between 7 and 8," he said, adding that a long term
Japanese study of Tehran came to similar conclusions.