Allen and Erik Olson of the University of Wisconsin at Madison published a paper on the matter in the Nov. 10 issue of Nature.
When Olson and Allen studied the seismographs of the first few
seconds of 71 earthquakes in California, Alaska, Taiwan and Japan, they
began to see evidence that the energy released by the initial seconds
of underground ruptures were scaled-down matches to the overall
magnitude of the quakes.
That's exactly not what the cascading dominoes model predicts.
"An alternative model is that the small beginning (of a quake) is
the last phase of some longer, slower, sub-seismic 'nucleation'
process," suggested geophysicist Rachel Abercrombie of Boston
University, who wrote a separate article in Nature commenting on Allen's and Olson's work.
That longer, slower process might be the gradual, silent and so far
undetected slipping of faults that set the stage for the final quake.
Regardless of the cause, the discovery is good news for earthquake
warning systems, said Allen. Even a few seconds of automated warning
time can be helpful when a big quake hits, he said.
Although most people may not be able to react fast enough, warning
systems in Japan, Taiwan and Mexico are already used to instantly warn
planes away from airports (in case runways are being damaged), to sound
alarms at schools and to automatically shut down processes at high-tech
manufacturers where a lot of damage could be done by shaking. All of
these things can save lives.
As for what it means for earthquake studies, the discovery is another
constraint that can be added to simulations of how faults work, said
That's particularly useful because constraints are in short supply to
geophysical modelers, he said, who have very little information about
exactly what is going on in the rupturing surfaces of faults during a