Japan has always boasted of a high standard of quake-resistant technology, but almost 12,000 structures were destroyed or damaged by the country's magnitude 7.2 quake -- many of them modern.
In particular, the collapse of several sections of an elevated expressway linking the cities of Kobe and Osaka jolted Japan's confidence in its earthquake engineering.
"It is similar to what had happened in San Francisco and Los Angeles, even though Japanese expressways were believed to be stronger," said Tadao Minami, a Tokyo University seismologist.
"We could have done better," said Motohiko Hakuno, a Toyo University engineering professor. "They could have been stronger."
Like their U.S. counterparts, Japan's elevated highways and railways are supported by columns containing dozens of vertical rods with "hoop" bandings for additional protection for side swayings.
Osamu Yoshizaki, an official in the Construction Ministry's section dealing with expressways, said parts of the Hanshin expressway had been beefed up bandings to meet the latest quake-resistance requirements.
It was not immediately known whether the collapsed portions had added bandings. Local news reports raised questions of insufficient banding.
"What happened is shocking, but all the expressways should meet the nation's strict quake resistance requirements," said the government's Public Works Research Institute director, Yasuyuki Koga.
The construction ministry has dispatched an investigator to the disaster site, and an official said earthquake-resistance standards may be reviewed depending on the assessment.
Some experts blamed the placing of too much emphasis on strength over flexibility for contributing to the degree of damage in the highway and other structures, but others disagreed.
"I don't think Japanese buildings and freeways are too rigid and stiff for strong earthquakes," said Tatsuya Azuhata, a ministry official in charge of architecture.
Yasuhiko Iwasaki, another official at the Construction Ministry's highway division, said the designed strength of Los Angeles expressways was only one-third of their Japanese counterparts.
"At the time of Northridge quake (a year ago) I thought their bridge columns were quite slender," he said. "Slender columns are flexible but less durable."
Japan is one of the world's most seismically active areas, and officials here like to point to long acquaintance with quakes and their effects.
"Japan is an earthquake nation that developed engineering from its unique experiences," Iwasaki said.
Some of the buildings that collapsed in Tuesday's quakes were large and modern, but many were old wooden homes.
Homes built after 1971 are required to be both strong and flexible enough to withstand earthquakes of 4-5 on the Japanese scale of 7. In the hardest hit areas, Tuesday's quake rated 6.
Reports have said that many of the homes destroyed were built before the 1971 standard was implemented.
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