In Japan earthquakes are a constant danger.
On an average day there are three strong enough for you to feel.
Predicting when an earthquake will take place is still just about
impossible. But Japanese scientists say they have come up with the next
best thing. They have developed a warning system that can alert you
before the shaking starts. The new system, which went live at the start
of October, is the first time a whole country has been protected in
this way.
It is an ambitious attempt to try to prevent large numbers of deaths
and injuries in the event of a serious earthquake like that which hit
Kobe in 1995 and killed more than 6,400 people.
In Japan earthquakes are a constant danger. On an average day there are
three strong enough for you to feel. Japan has an unrivalled network of
seismic sensors, more than 4,000 of them, some deep below the earth’s
surface. It is the density of that network that has allowed them to
create the new earthquake forecasting system.
When the earth ruptures down below a warning is sent to the surface so
fast it arrives before the shaking starts. “It’s not prediction but
early detection of an earthquake,” said Osamu Kamigaichi from Japan’s
Meteorological Agency.
“If we can detect the seismic wave at a station very close to the
epicentre, and then analyse and estimate the seismic intensity and the
arrival time of the wave, and if we can disseminate that information to
the public, then people can get ready for strong motion before it
arrives.”
When an earthquake begins a primary wave travels away from the
epicentre. This travels much faster than the more destructive secondary
waves.
Because Japan has so many seismic sensors it can detect the primary
wave as early as possible. New technology has been developed to analyse
that data almost instantaneously. Analysis of data from just one
station is all that is needed.
Once a wave of a certain intensity is detected an automatic warning is
sent to the state broadcaster NHK. Japan’s advanced telecommunications
infrastructure is what makes this possible.
An alarm goes off, and a message is automatically displayed on NHK
television channels and sounded on the radio. The message tells people
where the earthquake has taken place and how long they have to prepare
before the shaking starts. People can also buy alarm systems connected
via the internet to the Meteorological Agency systems.
“We expect that the length of the warning could be anything from a few
seconds to several tens of seconds,” says Kamigaichi. “But that could
be enough to make a difference.”
Smaller-scale warning systems exist in parts of Mexico, Taiwan and
Turkey. This is the first time it has been deployed on this scale.
It is already being tested in schools. The day I visited a primary
school in a Tokyo suburb the children were warned that a drill was
about to take place. Hanging over the back of their chairs in the
classrooms were little sacks.
When the alarm went off an announcement was broadcast over the
loudspeaker warning them that an earthquake was coming and beginning a
countdown so that they knew how long they had to take shelter.
The children reached into their sacks and got out little hoods made of
padded material. Most were metallic silver — they looked like little
Smurf hats. The children put the hoods on and crouched down under their
desks. The teacher pulled the curtains closed to try to protect them
from any shattered glass.
She then lifted up a clear plastic shield — the kind that riot police
use — over her head so that she could protect herself while she
remained standing, keeping an eye on her pupils.
The few seconds’ notice meant that all the precautions possible to take
were in place before the countdown reached zero. “This system has
helped us to make the children more aware of what they should do when
an earthquake strikes,” said the school’s headmaster Masaki Hayashi.
“It’s good for them for when they grow up. This is just in the earliest
stages so they are learning and being educated about this system but
when they are older it will be all over the place.”
It is not a foolproof system — like a weather forecast, they will not
always get it right. But the Japanese believe at the moment it is the
best chance they have to protect themselves.
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