JAPAN LEADS THE WAY WITH QUAKE-RESISTANT TECHNOLOGY
HIROKO NAKATA
The Japan Times
Wednesday, July 8, 2009
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.
Nagahide Kani, executive director of the Japan Society of Seismic
Isolation, speaks at his office in Tokyo’s Shibuya Ward in
June. YOSHIAKI MIURA PHOTO
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.