Curious cloud formations linked to quakes
* 11 April 2008
* From New Scientist Print Edition.
* Lynn Dicks
CAN unusual clouds signal the possibility of an impending earthquake?
That's the question being asked following the discovery of distinctive
cloud formations above an active fault in Iran before each of two
large earthquakes occurred.
Geophysicists Guangmeng Guo and Bin Wang of Nanyang Normal University
in Henan, China, noticed a gap in the clouds in satellite images from
December 2004 that precisely matched the location of the main fault in
southern Iran. It stretched for hundreds of kilometres, was visible
for several hours and remained in the same place, although the clouds
around it were moving. At the same time, thermal images of the ground
showed that the temperature was higher along the fault. Sixty-nine
days later, on 22 February 2005, an earthquake of magnitude 6.4 hit
the area, killing more than 600 people.
In December 2005, a similar formation again appeared in the clouds for
a few hours. Sixty-four days later, an earthquake of magnitude 6 shook
the region (International Journal of Remote Sensing, vol 29, p 1921).
Guo and Wang suggest that an eruption of hot gases from inside the
fault could have caused water in the clouds to evaporate. Another idea
is that ionisation may be involved: Friedemann Freund at the NASA Ames
Research Center in Moffett Field, California, recently demonstrated
that when rocks are squeezed, positively charged ions form in the air
above. The trouble is that ions usually help to form clouds, not
dissipate them.
The authors say that if recognisable cloud formations precede large
quakes, they could be used for prediction, but other seismologists are
sceptical. "There is no physical model that explains why something
would suddenly occur two months before an earthquake, and then shut
off and not occur again," says Mike Blanpied of the US Geological
Survey's Earthquake Hazards Program.
