Geologists from Stockholm University, Sweden, studied weekly measurements of groundwater chemistry in Northern Ireland over the past five years and found that the highest chemical levels appeared just four to six months before two separate earthquakes in 2012 and 2013. Both quakes were just 47 miles from the sampling site and measured over magnitude five. Previous scientific studies into earthquake prediction have included radon gas leaks, heat maps and unusual animal behavior, though none of these methods proved successful.
Groundwater, however, may be a more plentiful source to examine — especially in the United States, where around 40% of the population gets its drinking water from groundwater. However, Prof. Alasdair Skelton of Stockholm University, who led the project and published the research in Nature Geoscience, said it may be too soon to use the word “prediction.”
The study signifies that “something happens before earthquakes,” said Skelton. “Something is happening to the rocks before the earthquakes. We are highlighting groundwater chemistry as a promising target for future earthquake prediction studies.”
Skelton also pointed out that different rocks in other places could show different evidence of chemical changes, citing Iceland’s lone rock type, basalt, as a rock that may show unique measurements. As for the cause of the chemical changes, Skelton posited that other sources of water started mixing with the water the team sampled. This could have been caused by shaking or stress-induced cracking of the rocks underground.
Bruce Malamud of King’s College, London, UK, said that the results give “cautious optimism,” but more evidence is needed.
Ian Main, a seismologist from the University of Edinburgh, UK, agreed, saying, “There is a long way to go before observations such as these could be turned into diagnostic operational tools for forecasting earthquake probabilities.” Main also said that earthquakes, even the most deadly ones, can be set off by relatively small stresses in rock.