In the News
“ People have looked at certain materials and wondered why they have certain properties. Now they may be able to argue that
it’s because of this new symmetry. ” — manfred fiebig, page 9
Seismologists
in a rumble over
quake clusters
Japan’s catastrophe may be
latest in a series of big ones
story one
by alexandra Witze
Japan’s March 11 earthquake was the biggest ever recorded in that country and the costliest natural disaster in history, but in a way it
was nothing new. Three other quakes
of magnitude 8. 6 or greater have struck
worldwide in the past seven years — after
a gap of four decades.
Two U.S. Geological Survey scientists
contend that the Japan quake bolsters
their idea that the planet is experiencing
a spasm of great earthquakes, its second
since 1900. Other scientists say that any
apparent bunching is a statistical fluke
that disappears if the data are analyzed
in other ways. Researchers presented
their opposing vie ws on April 14 in Memphis, Tenn., at the annual meeting of the
Seismological Society of America.
On the face of it, large quakes certainly do seem to have been popping off
lately. The magnitude 9. 1 Sumatra quake
in 2004, which caused the disastrous
Indian Ocean tsunami, was followed by
a nearby magnitude 8. 6 quake the following year. A magnitude 8. 8 hit Chile
in February 2010 and the Japan quake, at
9.0, struck on March 11 of this year, leading many to question whether big quakes
are becoming more frequent.
Scientists say there’s not enough
people walk through rubble in Sendai, Japan, a month after the march 11 earthquake
and tsunami that destroyed the city’s coastal districts. Some geologists argue that
the event may be seismically linked to other recent major earthquakes.
evidence to support that idea. But big
quakes may at least be coming in groups.
Some earthquake clusters are clearly
related; after a large quake, aftershocks
on connected faults continue to rattle
the area. And large quakes can also trigger
separate smaller tremors relatively close
to the original quake (SN Online: 3/28/11).
But Charles Bufe of the USGS office in
Golden, Colo., argues that Sumatra, Chile
and Japan represent an unusual grouping.
In 2005, Bufe and his colleague David
Perkins argued that a similar clus-
ter occurred between 1952 and 1964,
anchored by a magnitude 9.0 in Kam-
chatka, Russia, at its beginning and a
magnitude 9. 2 in Alaska at its end. The
Kamchatka quake was the first magni-
tude 9 or greater since 1900, when sci-
entists began recording seismic activity
worldwide. This cluster also included the
largest quake ever recorded, a magnitude
9.5 monster that struck Chile in 1960.
www.sciencenews.org
May 7, 2011 | science news | 5
