Changes in animal activity could help forecast earthquakes

Study conducted in Peru's Yanachaga National Park correlates changes in behavior of birds and small mammals with atmospheric ionization caused by rock friction deep underground.

By José Tadeu Arantes

Agência FAPESP – That animals change their behavior hours or days before catastrophic events such as earthquakes has been known for some time. Elephants were much in the news after the 2004 Boxing Day quake and tsunami in Southeast Asia. The animals were reported to have charged to high ground just before the disaster. Many human lives were saved thanks to this phenomenon. However, events like this had never been rigorously and conclusively documented, nor had a cause-and-effect relationship been established between changes in animal behavior and measurable physical phenomena.

This has now been done, thanks to a research project conducted by Rachel Grant of Anglia Ruskin University in the UK, Friedemann Freund of the SETI Institute, working at the US National Aeronautics & Space Administration (NASA), and Jean-Pierre Raulin of the Mackenzie Radio Astronomy & Astrophysics Center (CRAAM) in Brazil. An article reporting their findings, entitled “Changes in Animal Activity Prior to a Major (M=7) Earthquake in the Peruvian Andes”, has been published by the journal Physics and Chemistry of the Earth.

Physicist Jean-Pierre Raulin, a professor at Mackenzie Presbyterian University in São Paulo, participated in the study in the context of the research project “Monitoring solar activity and the South Atlantic Magnetic Anomaly (SAMA) using a network of very low frequency (VLF) receivers – SAVNET South America VLF network”, supported by FAPESP.

“Our study correlated changes in the behavior of birds and small mammals in Peru’s Yanachaga National Park with disturbances in the earth’s ionosphere. Both phenomena were observed several days before the magnitude 7.0 Contamana earthquake struck the Peruvian Andes in 2001,” Raulin told Agência FAPESP.

The animals were monitored by a series of motion-triggered cameras. “To avoid interfering with their behavior, we used cameras that were activated automatically whenever they detected animal movements and took pictures using infrared flashes, which don’t disturb the animals,” Raulin said. On a typical day, the cameras recorded between five and 15 animal sightings, but in the 23-day period that preceded the earthquake they recorded five or fewer sightings. Indeed, for five of the seven days immediately before the earthquake, no animal movements were recorded at all.

At the same time, while monitoring the propagation properties of very low frequency (VLF) radio waves over the area around the epicenter, the researchers detected disturbances in the ionosphere two weeks before the earthquake. A particularly large ionospheric disturbance observed eight days prior to the quake coincided with the second decrease in animal sightings.

The researchers proposed a hypothetical correlation between the two phenomena. Massive generation of positive ions by subterranean rock friction during the period prior to the earthquake may have caused both the disturbances measured in the ionosphere and the changes in animal behavior, they surmised. In this case the friction was due to subduction (sliding) of the Nazca tectonic plate under the South American plate far beneath the northern Andes.

Large concentrations of positive ions in the atmosphere are known to cause increased levels of serotonin in the blood stream of animals and humans. This can lead to “serotonin syndrome”, whose symptoms include restlessness, hyperactivity and confusion. The phenomenon is similar to the easily observable agitation that occurs in humans before a storm, when the concentration of electrons at the base of the storm clouds also causes a build-up of positive ions in the layer of the atmosphere closest to the ground, generating an intense electric field at the ground-to-air interface.

“In the case of earthquakes, positive charges form in the subsoil owing to rock stresses and migrate rapidly to the surface, resulting in massive air ionization,” Raulin said. “In a matter of hours, the positive ions thus formed reach the bottom of the ionosphere, located some 70 km above ground level. This huge injection of ions must have caused the fluctuations we detected in the electron density of the lower ionosphere. On the other hand, subterranean transit of positive charges due to a sort of ‘edge effect’ tends to lead to a build-up of ionization near local topographical elevations, precisely where the cameras were located. Our hypothesis was that the animals fled to lower altitudes, where they would have been exposed to fewer positive airborne ions, in order to avoid the undesirable symptoms of serotonin syndrome.”

“We believe both anomalies were due to a single cause: seismic activity triggering stress in the earth’s crust and leading, among other things, to massive ionization of the ground-to-air interface” said Grant, the paper’s lead author. “We hope our work will stimulate further research in this area, potentially helping with seismic risk forecasting.”

Leaving aside the researchers’ observations of animal behavior, their findings show that seismic forecasting could make good use of air ionization detection by monitoring the atmosphere’s electric field. “We already have detectors installed in Brazil, Peru and Argentina,” Raulin said. “We have short-term plans to install atmospheric electric field sensors at locations where major seismic activity is expected to occur. We could use these to predict earthquakes perhaps two or more weeks in advance. The SAVNET network detected fluctuations in the ionosphere 12 days before the January 2010 quake in Haiti. The results were published in the journal Natural Hazards and Earth System Sciences (NHESS).”