Scientists have been able to capture and document how the behaviour of wild animals changes prior to an earthquake – a development which may help with short-term seismic forecasting.
The study, led by Dr Rachel Grant of Anglia Ruskin University, used data gathered from a series of motion-triggered cameras located in the Yanachaga National Park in Peru.
The research found that significant changes in animal behaviour began 23 days before the magnitude 7.0 Contamana earthquake struck the region in 2011.
On a typical day the cameras would record between 5-15 animal sightings. However, within the 23-day period in the run-up to the earthquake, they recorded five or fewer sightings.
For five of the seven days immediately before the earthquake, no animal movements were recorded at all, which was incredibly unusual for this mountainous rainforest region.
At the same time, by recording the reflection of very low frequency (VLF) radio waves above the area surrounding the epicentre, the scientists detected disturbances in the ionosphere, which started two weeks before the earthquake.
A particularly large fluctuation was recorded eight days prior to the quake, coinciding with the second significant decrease in animal activity observed in the pre-earthquake period.
Prominent among the most likely causes for the unusual animal response are positive airborne ions, which are known to be generated in large numbers at the earth’s surface when rocks deep below are subjected to increasing stresses during the build-up to an earthquake, researchers said.
Positive ions in the air lead to disagreeable side effects in animals and humans, such as “serotonin syndrome”. This is caused by an increase in the serotonin levels in the bloodstream, and can lead to symptoms such as restlessness, agitation, hyperactivity and confusion.
Therefore the injection of positive airborne ions into the earth’s atmosphere prior to major seismic activity can be expected to have a profound effect on mammals and birds, in particular those living on the ground and in burrows.
“The camera traps were located on a ridge at an altitude of 900m. If air ionisation occurred, it is likely that it was particularly strong along such a ridge,” said Professor Friedemann Freund of the Search for extraterrestrial intelligence Institute (SETI).
“Hence, the animals would have escaped to the valley below, where they were exposed to fewer positive airborne ions.
“With their acute ability to sense their environment, animals can help us understand subtle changes that occur before major earthquakes.
“These changes, that we are now able to measure, express themselves in many different ways at the earth’s surface and above,” Freund said.