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Wednesday, July 8, 2009
G8 ITALY SUMMIT
Japan leads the way with quake-resistant technology
Lessons from deadly '95 earthquake could save lives worldwide
When a massive earthquake hit the western part of Japan more than a decade ago, a highway collapsed, railroads and telephone lines were partially cut, and many buildings were toppled.
The 1995 7.3-magnitude Great Hanshin-Awaji Earthquake wreaked havoc on Hyogo Prefecture. In the biggest natural disaster in postwar Japan, 6,434 people lost their lives — some crushed to death under buildings, others dying in the fires caused by the temblor.
The earthquake changed people's minds in Japan, and Italy, which has highly advanced quake-resistant technologies, should do more to disseminate these technologies, said Nagahide Kani, executive director of the Japan Society of Seismic Isolation, an industry group engaged in developing quake-resistant technology.
"Before the quake, people wouldn't accept seismic-isolation technologies," he told The Japan Times in a recent interview. "But the number of buildings introducing the technologies jumped in 1995," he said.
In Italy, the host country of this year's Group of Eight summit, a 6.3-magnitude earthquake hit L'Aquila on April 6, killing more than 290 people and injuring over 1,000.
Many of the brick buildings that help to create the historic atmosphere of L'Aquila crumbled as few of them employed quake-resistant systems, experts said. As a result, more than 10,000 buildings were damaged or destroyed.
"Italy's seismic-isolation technologies are very advanced, but they are not wide spread," Kani said.
In Japan, thanks to the huge earthquake in 1995, quake-resistant technologies grabbed the spotlight and more Japanese buildings introduced the seismic-isolation system, or base-isolation system, as it protects a structure by installing components between a building and its foundation, decoupling it from the shaking ground.
Figures prove how Japan moved to cope with possible massive earthquakes.
In 1982, there was only one building that employed the system — a two-story housing unit in the city of Yachiyo, Chiba Prefecture, west of Tokyo. The number gradually rose to 80 buildings by 1994, but after the 1995 earthquake, the figure soared to 2,200 buildings in 2009.
Quake-resistant systems for housing are also widely used in Japan. Some 5,000 Japanese houses have introduced vibration-isolation technologies, Kani said.
The number in Japan stands out even among earthquake-prone countries. In Italy, only 100 buildings have introduced seismic-isolation technologies. Looking at other countries, there are 700 in China, 600 in Russia, 100 in the United States, 50 in Taiwan, 30 in Armenia and 10 in New Zealand. In future, China is likely to see more buildings introduce the quake-resistant system as a massive earthquake hit China's Sichuan province in May 2008, Kani added.
When there is such a disaster, the destruction of hospitals is a double blow. Collapsed hospitals endanger patients who cannot escape the crumbling structures while the damaged medical facilities hamper treatment of the injured.
In the Great Hanshin-Awaji Earthquake in 1995, the fifth floor of the seven-story Kobe City Hospital Organization Medical Center West Hospital was crushed, burying more than 40 patients and nurses, although most of them were rescued, according to local media reports at the time.
"It is terrible for hospitals to collapse because they are supposed to be where victims can be helped," said Kani.
Thanks to quake-resistant technologies, Kurihara Central Hospital in Miyagi Prefecture, on the other hand, avoided a collapse in a big earthquake in Miyagi and Iwate prefectures in 2008, enabling the hospital to serve as the hub for rescuers.
Now certain types of buildings in Japan are increasingly introducing the seismic-isolation system, such as hospitals, art museums, high-rise housing, embassies, and data centers that preserve customer information for banks, life insurers and nonlife insurers.
Production plants are also starting to introduce the system, after the major impact on Japanese industry of the two recent earthquakes in 2004 and 2007.
"Considering the importance of sustaining corporate activities, companies don't want to do business with those who do not take risk management steps," Kani said.
Though quake-resistant technologies are widely disseminated in Japan, they are not originally from here. The first such technology, called "rubber bearing," was invented in New Zealand in 1977, and introduced to an office building there and a courthouse in the United States, Kani said, adding that it had a huge impact on the industry.
This technology using rubber bearings is most popular in Japan and it is used around the world, according to Kani. By installing rubber bearings, composed of layered thin rubber and thin steel plates, under a structure, the building can move flexibly in a horizontal direction and has strong resistance to quakes. Moreover, the bearings do not buckle even under a heavy building because of the number of steel plates, Kani said. It has been introduced in various structures such as office blocks, housing and the administrative buildings of Japan's central government.
Two other systems were invented later that are suitable for lighter buildings and less expensive, Kani said.
About a decade after the "rubber bearing" technology was introduced, another type of base-isolation system, called a "sliding isolation system," or a "slider," was developed. The system, which is also placed under a building, consists of a bearing pad on top of a curved surface. In a quake, this bearing pad slides on the curved surface to absorb tremors and support the building.
Later, another technology, called the "rotating ball bearing" system, was introduced. The system uses ball bearings that slide on parallel rails.
Now the focus is on how to apply such quake-resistant technologies to existing buildings, including old structures, which requires a high degree of skill, Kani said.
Rather than isolating buildings from the ground, there are new technologies to absorb shocks on buildings by using particular materials, and components for pillars and walls. In addition, some buildings even employ a system to control shocks that uses computers. The number of buildings with such new technologies will increase in the near future, Kani said.
"The development of quake-related technologies will never end," he said.
Despite the development of the technologies, Japan needs to work hard to cope with possible earthquakes.
The education ministry warned June 16 that more than 7,300 school buildings are at high risk of collapse in the event of a powerful earthquake. A survey by the ministry on the nation's 124,976 public schools also found that the quake resistance of 41,206 buildings is insufficient. The ministry said 7,309 could crumble if hit by a quake measuring an Upper 6 on the Japanese seismic scale of 7.