Jobs • Cars • Real Estate • Apartments • Shopping • Classifieds • Dating |
top jobsReceptionist/Order Taker FT. Apply in... LEGAL SECRETARY/ASST. for a land development... Amber Lights, Tucson's premier senior living... NEED HOUSE KEEPER for house cleaning and... SPEECH PATHOLOGIST starting range $44,652-$55,332... Amber Lights, Tucson's premier Senior Living... NEED PART TIME EXPERIENCED MACHINISTS CALL...NationScientists say quake's strength can be measured in first secondsTHE ASSOCIATED PRESS
Tucson, Arizona | Published: 11.10.2005
LOS ANGELES - Scientists have found a way to
estimate an earthquake's ultimate strength by analyzing the initial
seconds of a rupture - a step that could one day provide early earthquake
warning.
Currently, a quake's magnitude - or how much
energy is released - is determined after the shaking stops, usually
minutes after an event.
But researchers from the University of
California-Berkeley say the measurements of seismic waves soon after a
quake can signal whether it will be minor or a monster.
They say the information could possibly be
used in an alert system to give seconds to tens of seconds of advance
notice of an impending quake - enough time for schoolchildren to take
cover, power generators to trip off and valves to shut on pipelines.
"We're not taking about a massive amount of
time," said Richard Allen, an assistant professor of earth and planetary
science, who led the study. "But one can use our approach to come up with
a magnitude before people have felt the ground shaking."
Details appear in today's issue of the journal
Nature.
The study suggests different magnitude quakes
begin in different ways, said Lucy Jones, the scientist in charge of the
U.S. Geological Survey in Pasadena, who was not part of the study.
But Jones was skeptical that the information
can be reliably used to create an early warning system. The United States
is still years away from an alert system because of fears of false alarms
and disagreement among scientists about what physical forces cause an
earthquake to turn into a big one.
Analyzed 71 major quakes
In the study, Allen and colleagues
analyzed records of 71 major Pacific Rim quakes in the past decades
including 24 events that were greater than a magnitude-6.
Using a mathematical model, they were able to
estimate a quake's size to within one magnitude unit from as little as
four seconds of data of the frequency of the energy in the primary wave.
These low-energy waves typically cause a jolt, signaling the occurrence of
a quake.
Earlier research conducted by Allen showed
that the first few seconds after a quake can be used to estimate quakes
smaller than magnitude-6.
Allen is currently testing the model in
real-time using an intricate network of seismic instruments scattered in
Northern California.
|