TEHRAN (Reuters) - Iranian scientists said on Thursday they had revised the magnitude of an earthquake that struck the southeastern city of Bam last Friday to about 6.8 from the previously reported 6.3 on the Richter scale.
The Housing and Construction Research Center said the analysis of 18 monitoring stations in and near the quake zone showed the quake was not only more powerful than first thought but also that its epicenter was directly under the city.
The pre-dawn earthquake destroyed most of the buildings in Bam, 625 miles southeast of Tehran, and killed an estimated 30,000, although some officials have warned the death toll could rise to 50,000.
"Based on data from 18 monitoring sites in and near Bam we have now retrieved, the earthquake registered 6.8," Jafar Shoja Taheri, head of seismology research at a Mashhad University told state television.
"It is more than the 6.3 previously reported," he said.
The U.S. Geological Survey issued a preliminary report last week saying the Bam quake measured at 6.6 magnitude.
Shoja Taheri, also a member of the state housing and construction research body, said that of the 30 seismological monitoring stations in and near Bam, only 18 have been found.
"One of the monitored sites was located in the Bam governor's office," he added. "That data showed that the earthquake's epicenter was directly beneath Bam."
Some Tehran scientists have said the quake was about 10 miles below the surface. About 90 percent of the mud brick-style buildings in the ancient city were destroyed.
Shoja Taheri said that data were still provisional and further analysis could lead to another revision.
"It will take time to survey and analyze all the data and come to a final conclusion of the magnitude," he said.
Iran Experts Raise Bam Quake Magnitude to 6.8
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TEHRAN (Reuters) - Poor design, primitive materials and widely ignored building codes were prime causes of the high death rate in the Bam earthquake, Iranian officials and foreign experts said on Tuesday.
In stark contrast to a tremor of similar strength last week in California that killed just two people, the toll in Friday's Iranian quake could reach about 50,000.
Iran's building codes have been tightened after quakes in recent decades killed tens of thousands. But officials and independent scientists say enforcement is woefully inadequate.
Bahram Akasheh, geophysics professor at Tehran University, noted the California quake on December 22 had almost the same magnitude and depth as the Iranian tremor, which measured 6.3 on the Richter scale and was centerd 16 km (10 miles) below ground.
"The question is why were only two killed in California but so many in Iran?" he said. "The answer is simple. The type of construction is totally different. There are building codes here but they are not followed. The laws are there, but only in theory. No one pays any attention. No authorities control construction."
President Mohammad Khatami said there would be an inquiry and anyone who had violated state codes would be punished. Two hospitals, a prison and other state buildings collapsed or were badly damaged.
"We will investigate the houses which were built in recent years, especially government buildings," Khatami said. "These buildings shouldn't have collapsed. Those who are to blame will be seriously punished."
While Iranian officials keep a close eye on many aspects of daily life, there is little policing of construction.
"I don't think there are any shortcomings with our policies and construction codes," said Mohsen Rezaei, secretary of Iran's powerful Expediency Council.
"It is the construction managers who do not implement the codes. There is not enough supervision of construction and engineering."
Ali Bakhshi, a civil engineering professor in Tehran, said some builders disregarded the codes to make bigger profits.
MUD-BRICK BLAMED
Fingers are also being pointed at the mud bricks common in towns like Bam. They are cheap and popular because they keep houses cool in summer and warm in winter. But they crumble easily, suffocating many who survive the actual quake.
"In Iran...the houses are essentially made of dust," said Enzo Boschi, president of the National Institute of Geophysics in quake-prone Italy. "When buildings made of concrete collapse there are pockets of air where you can breathe and survive two, three, maybe even five days. But with mud houses, and the dust they produce when collapsing, you die much quicker."
But experts say that is only part of the problem. They warn even Tehran, where modern steel-framed concrete buildings are common, would be vulnerable to quakes of around 6.0 on the Richter scale. A reading of at least 7.0 is often seen as the threshold for major loss of life.
With suitable construction methods, cities can survive much greater earthquakes. A tremor measuring 8.0 caused just 500 injuries and no deaths in Japan in September.
"Earthquakes per se are not dangerous, it's how buildings are constructed and the quake's timing that cause deaths," said Boschi. "The Bam quake happened in the morning when people were all still in bed, unconscious and defenseless."
Stavros Joannides, a Cypriot structural engineer who worked in Iran in the 1970s, said mud bricks were not flexible enough.
"Once that elasticity is lost and there is no steel, no reinforced concrete, the building will give," he said. "Without warning. Mud brick doesn't start dropping bits of plaster or brick like a concrete house will. It comes down at once."
In stark contrast to a tremor of similar strength last week in California that killed just two people, the toll in Friday's Iranian quake could reach about 50,000.
Iran's building codes have been tightened after quakes in recent decades killed tens of thousands. But officials and independent scientists say enforcement is woefully inadequate.
Bahram Akasheh, geophysics professor at Tehran University, noted the California quake on December 22 had almost the same magnitude and depth as the Iranian tremor, which measured 6.3 on the Richter scale and was centerd 16 km (10 miles) below ground.
"The question is why were only two killed in California but so many in Iran?" he said. "The answer is simple. The type of construction is totally different. There are building codes here but they are not followed. The laws are there, but only in theory. No one pays any attention. No authorities control construction."
President Mohammad Khatami said there would be an inquiry and anyone who had violated state codes would be punished. Two hospitals, a prison and other state buildings collapsed or were badly damaged.
"We will investigate the houses which were built in recent years, especially government buildings," Khatami said. "These buildings shouldn't have collapsed. Those who are to blame will be seriously punished."
While Iranian officials keep a close eye on many aspects of daily life, there is little policing of construction.
"I don't think there are any shortcomings with our policies and construction codes," said Mohsen Rezaei, secretary of Iran's powerful Expediency Council.
"It is the construction managers who do not implement the codes. There is not enough supervision of construction and engineering."
Ali Bakhshi, a civil engineering professor in Tehran, said some builders disregarded the codes to make bigger profits.
MUD-BRICK BLAMED
Fingers are also being pointed at the mud bricks common in towns like Bam. They are cheap and popular because they keep houses cool in summer and warm in winter. But they crumble easily, suffocating many who survive the actual quake.
"In Iran...the houses are essentially made of dust," said Enzo Boschi, president of the National Institute of Geophysics in quake-prone Italy. "When buildings made of concrete collapse there are pockets of air where you can breathe and survive two, three, maybe even five days. But with mud houses, and the dust they produce when collapsing, you die much quicker."
But experts say that is only part of the problem. They warn even Tehran, where modern steel-framed concrete buildings are common, would be vulnerable to quakes of around 6.0 on the Richter scale. A reading of at least 7.0 is often seen as the threshold for major loss of life.
With suitable construction methods, cities can survive much greater earthquakes. A tremor measuring 8.0 caused just 500 injuries and no deaths in Japan in September.
"Earthquakes per se are not dangerous, it's how buildings are constructed and the quake's timing that cause deaths," said Boschi. "The Bam quake happened in the morning when people were all still in bed, unconscious and defenseless."
Stavros Joannides, a Cypriot structural engineer who worked in Iran in the 1970s, said mud bricks were not flexible enough.
"Once that elasticity is lost and there is no steel, no reinforced concrete, the building will give," he said. "Without warning. Mud brick doesn't start dropping bits of plaster or brick like a concrete house will. It comes down at once."
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Awesome satellite picture of Bam taken on the 27th of December
Awesome satellite picture of Bam taken on the 27th of December
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