Six days before a devastating 6.3 earthquake reduced the picturesque Italian town of L’Aquila to rubble in 2009 – and with 281 people found dead in the first three days and 28,000 relocated – scientists were noticing that frogs had started to leave their ponds. Now, more than two years later, a picture is beginning to emerge.
Animals may sense chemical changes in groundwater that occur when an earthquake is about to strike.
A new report in the International Journal of Environmental Research says that rocks in the Earth’s crust release charged particles when they’re getting ready to slip and set off an earthquake, and that these particles react with the groundwater. Animals who live in or near the water sense these changes in its chemistry, so they might sense this days before the quake happens.
Stories of animals seeming to sense an earthquake are hardly new.
- Just after a large earthquake in San Diego, local residents discovered dozens of Humboldt squid washed up on beaches. These deep sea squid are usually found at depths of between 200 and 600m
- Deep-sea fish rising to the surface have been observed on numerous occasions, as have fish jumping out of the water.
- Crabs have been seen leaving the water in large numbers prior to earthquakes.
But observations like these are mostly anecdotal, as well as hard to verify.The L’Aquila story is different. Rachel Grant, a biologist from the Open University, was right there, monitoring the toad colony as part of her Ph.D. project.
“It was very dramatic,” she recalled. “It went from 96 toads to almost zero over three days.”
Then she wrote about it in the Journal of Zoology:
Although our study site is 74 km from L’Aquila, toads showed a dramatic change in behavior 5 days before the EQ, abandoning spawning and not resuming normal behavior until some days after the event.
Grant’s colleague, Friedemann Freund, explains what the team believes is happening:
“Positive airborne ions are known in the medical community to cause headaches and nausea in humans and to increase the level of serotonin, a stress hormone, in the blood of animals. They can also react with water, turning it into hydrogen peroxide.”
Could this lead scientists to be able to predict earthquakes? They’d need to be in the right place at the right time, but, in principle, yes.
“Once we understand how all of these signals are connected, if we see four of five signals all pointing in [the same] direction, we can say something is about to happen.”
In an audio interview with the BBC, Grant describes what happened.