Researchers
the world over are seeking reliable ways to predict earthquakes,
focusing on identifying seismic precursors that, if detected early
enough, could serve as early warnings.
New research, published this week in the journal Applied Physics Letters,
suggests that ozone gas emitted from fracturing rocks could serve as an
indicator of impending earthquakes. Ozone is a natural gas, a byproduct
of electrical discharges into the air from several sources, such as
from lightning, or, according to the new research, from rocks breaking
under pressure.
Scientists in the lab of Raúl A. Baragiola, a professor of engineering physics in the University of Virginia School of Engineering and Applied Science,
set up experiments to measure ozone produced by crushing or drilling
into different igneous and metamorphic rocks, including granite, basalt,
gneiss, rhyolite and quartz. Different rocks produced different amounts
of ozone, with rhyolite producing the strongest ozone emission.
Some
time prior to an earthquake, pressures begin to build in underground
faults. These pressures fracture rocks, and presumably, would produce
detectable ozone.
To
distinguish whether the ozone was coming from the rocks or from
reactions in the atmosphere, the researchers conducted experiments in
pure oxygen, nitrogen, helium and carbon dioxide. They found that ozone
was produced by fracturing rocks only in conditions containing oxygen
atoms, such as air, carbon dioxide and pure oxygen molecules, indicating
that it came from reactions in the gas. This suggests that rock
fractures may be detectable by measuring ozone.
Baragiola
began the study by wondering if animals, which seem—at least
anecdotally—to be capable of anticipating earthquakes, may be sensitive
to changing levels of ozone, and therefore able to react in advance to
an earthquake. It occurred to him that if fracturing rocks create ozone,
then ozone detectors might be used as warning devices in the same way
that animal behavioral changes might be indicators of seismic activity.
He said the research has several implications.
“If
future research shows a positive correlation between ground-level ozone
near geological faults and earthquakes, an array of interconnected
ozone detectors could monitor anomalous patterns when rock fracture
induces the release of ozone from underground and surface cracks,” he
said.
“Such
an array, located away from areas with high levels of ground ozone,
could be useful for giving early warning to earthquakes.”
He
added that detection of an increase of ground ozone might also be
useful in anticipating disasters in tunnel excavation, landslides and
underground mines.
Baragiola’s co-authors are U.Va. research scientist Catherine Dukes and visiting student Dawn Hedges.
Ozone generation by rock fracture: Earthquake early warning?
