Ozone, a natural gas, is a byproduct of electrical discharges into the air from several sources, such as from lightning or, the new research suggests, from rocks fracturing as stress builds up in earthquake faults under pressure, scientists say.
Researchers at the University of Virginia School of Engineering and Applied Science conducted 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, they said, with rhyolite producing the strongest ozone emission.
"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," said Raul A. Baragiola, professor of engineering physics.
"Such an array ... could be useful for giving early warning to earthquakes."