On Thursday, more than 80 people, mostly children,
were killed in the Turkish province of Bingol after a
school building collapsed during a massive earthquake.
In the wake of the quake, a new study has emerged that
might have come up with an early-warning system to
prevent such disasters from happening again.
Earthquakes are nature's scary surprises. By the time
you realize you're experiencing a temblor, the shaking
is often half over, leaving you to wonder if another one
will follow quickly.
Long-time residents of earthquake country swear that
their animals sometimes alert them by acting strangely,
while others warn that it's "earthquake weather" when
the mercury rises.
Soon there may be a more scientific warning for
residents of southern California.
Buying precious time In the May 2 issue of
Science, researchers describe an early-warning
system for the region that could give as much as 40
seconds' notice before a strong ground motion was due.
Once in place, the system could help stem disaster by
giving people enough time to take shelter, evacuate
buildings, stop trains, and divert aircraft.
The amount of warning time will depend on how far a
person is from the epicentre, says Richard Allen, a
professor of geology and geophysics at the University of
Wisconsin-Madison and the lead author of the paper. "If
you are at the epicentre, we're talking about zero, one,
maybe two seconds. If you are 60 kilometres [37 miles]
away, we are talking about 20 seconds of warning."
New system makes use of the TriNet
network The proposed new early warning system,
called ElarmS, uses a network of 155 seismic stations
already in place in southern California, called TriNet,
now part of the California Integrated Seismic
Network.
"TriNet has two rapid reporting systems," Allen says.
"CUBE is a paging system and it gives the magnitude and
location of the earthquake. The other is the Shake Map -
it shows the distribution of the ground motion across
southern California. They're available within
minutes."
Measuring P and S waves TriNet stations
record ground motion, including P waves, the first
seismic arrival from an earthquake, and the usually
larger amplitude S waves, which are responsible for most
of the damage to buildings during a quake.
"We are using the P waves to locate and determine the
magnitude of the earthquake and, based on that, issue a
warning," Allen says.
To test the concept of ElarmS, Allen and his
co-author, Hiroo Kanamori of the California Institute of
Technology in Pasadena, gathered waveform data from 53
recent California earthquakes and estimated the
magnitude from the P waves and other data.
Early-warning systems around the
globe Early-warning systems are already in place
in other locations, Allen says. Mexico City, for
instance, has an early warning system based on
measurements of ground motion along the coast, where the
quakes tend to occur, and can transmit alerts to the
city before the ground motion arrives.
Southern Californians live above many active faults,
some of which are directly below densely populated
metropolitan areas. So measuring the P waves, rather
than waiting for the S waves or waiting until the ground
motion reaches a particular threshold, as other systems
do, is a better idea, Allen says.
The next step, Allen says, is to test the new system
in the "real time system that Trinet already runs" to
see how accurate the magnitude estimates based on P
waves are.
But is it logistically feasible? Other
experts praise the paper's scientific value but question
whether the early warning system will be logistically
feasible.
"The paper is excellent work," says Bill Spencer, a
professor of civil engineering at the University of
Illinois at Urbana-Champaign. The system might work
best, he adds, in conjunction with buildings equipped
with shock absorber-like systems that cause the building
to adapt to the magnitude of the quake to sustain the
least damage. "These are already inside some large
buildings," he says.
"Scientifically it's a very good paper," agrees David
Wald, a seismologist with the United States Geological
Survey in Golden, Colorado, who helped develop the Shake
Map. "But I have reservations about implementation of an
early-warning system." Putting the system into practice,
he says, would involve complicated logistics.
"People who would need the most warning would get
the least." "You could stop elevators at a
certain floor [if the warning was issued]. You could
install electronic freeway signs, saying 'Don't go over
this overpass.' But a lot of things rely on human
response." And that might not be so predictable, he
says.
"The amount of [warning] time this system would
provide is very little for the people closest," he says.
"People who would need the most warning would get the
least."
Yet, Allen counters that any warning is better than
none. After the Northridge quake of 1994, he says,
"buildings were red-tagged up to 60 kilometres from the
epicentre." In the 1989 Loma Prieta quake, highways and
buildings 50 miles from the epicentre collapsed. -
(HealthScout News)
Read more: Trapped
under rubble: How long can one survive? Time
to Pitch Those Y2K Foods |