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computer software can detect the onset of an earthquake and sound a
warning before a quake's most destructive shaking arrives,
scientists are reporting today.
If the system is put into effect, the warning will be short —
tens of seconds at most — but it may give workers and students time
to duck under desks, air traffic controllers the chance to wave off
landing planes and officers a few seconds to lower barriers to keep
cars off bridges and overpasses.
For now, though, experts are unsure just how they will use the
warnings and acknowledge that false alarms may create problems.
"Just ringing a bell can cause a lot of panic," said Dr. Richard M.
Allen, a professor of geology and geophysics at the University of
Wisconsin.
Writing in today's issue of the journal Science, Dr. Allen and
Dr. Hiroo Kanamori, a professor of geophysics at the California
Institute of Technology, describe a computer algorithm that analyzes
seismic data gathered from 150 sensors already deployed around
Southern California and continuously sent to a computer at
Caltech.
Similar systems could also be put in place in other
earthquake-prone areas. Dr. Allen said that he and Dr. Kanamori were
currently researching whether a sparser and less expensive network
of sensors would still provide useful warning.
"If we can do that, we can go to the regions that don't have the
resources," Dr. Allen said. "I would argue these kinds of systems
could be very useful in places like Turkey."
Earthquakes shake rocks in two different ways. The warning system
focuses on one type of seismic wave that moves quickly — 3.5 miles a
second — but causes little damage, resembling the waves that travel
along a Slinky toy when one end is pushed and pulled quickly. The
slower, more destructive waves resemble the waves when a Slinky is
shaken side to side.
The computer program, running on the computer at Caltech, detects
the onset of an earthquake in the faster-moving seismic waves, and
within seconds, calculates the epicenter and estimates the
magnitude. A warning can then be issued. A location 35 miles from
the epicenter will get about a 15-second warning before the slower,
damaging seismic waves arrive.
The technology appears to be arriving before emergency officials
have had time to think through how warnings should be issued and who
should receive them. Also unresolved are questions like who would
issue the warnings.
"When you start thinking about the next step, it really is a
quagmire," said Dr. David Wald, a seismologist with the United
States Geological Survey. "Most people don't know what to do with
that information. We're not ready for it."
The researchers are considering a system that will send out the
warnings via the Internet.
Patrick Small, the computer programmer installing Dr. Allen and
Dr. Kanamori's algorithms, said he hoped to finish a prototype of
software by the end of the summer that would run on personal
computers and receive and display earthquake warnings from the
Caltech computer.
Mr. Small is also working to speed up his computer program.
Zooming in on the epicenter now takes 15 to 40 seconds. "I think we
can get it down to about 5 seconds," he said.
The researchers will begin an internal test phase to evaluate the
accuracy and effectiveness of the warnings.
"What I'm working on is definitely not for the public," Mr. Small
said, meaning that it is not ready for practical use.
While the technology is unfinished but progressing quickly, the
policy decisions have hardly begun.
"We've thought about it," said Dr. John Filson, manager of the
earthquake hazard program at the Geological Survey. "And it's a
difficult issue. To turn it into an operational system is going to
take some thoughtful planning with the local emergency response
officials."
At first, the warnings may be most easily used in controlled
environments like schools and hospitals, where false alarms would
probably not be more than a nuisance. "We could possibly avoid
injuries in our schools by training our children to get beneath
their desks and away from the windows," said James Goltz, a research
specialist in California's Office of Emergency Services.
It would eventually be possible to design "smart" buildings that
upon receiving a warning could take actions like moving elevators to
the nearest floor and opening the doors to prevent people from being
trapped.
Mr. Goltz said he thought that if an agency started issuing
earthquake warnings, it would be hard to restrict that information
to a limited group of people. "I think as this technology become
available, we do have an obligation to promote its availability to
groups that can use it, everyone ultimately," he said.
Earthquake warning systems already exist in a few areas,
including Mexico City. There, the system is simpler, because the
earthquake originates from faults nearly 200 miles to the southwest
of the city and seismometers can easily detect the rumblings before
they reach Mexico City. The system has generated some false
alarms.
In the Los Angeles area, faults crisscross through the populated
areas. Even with a fully functioning system, people at the epicenter
would receive almost no warning.
"Early warning is not a panacea for earthquake losses," said Dr.
Wald of the Geological Survey.