One person reported how Kaikoura's seals were unusually noisy shortly before the 2016 7.8 earthquake. But scientists say there's nothing to back such links. Photo / NCTIR
One person reported how Kaikoura's seals were unusually noisy shortly before the 2016 7.8 earthquake. But scientists say there's nothing to back such links. Photo / NCTIR
Scientists say there's no strong evidence to back the age-old myth that animals can sense big quakes before we do.
In quake-prone New Zealand, the idea that animals can predict impending disasters has long persisted; after 2016's Kaikoura Earthquake, one camper reported to Newstalk ZB how some nearby seals started"making a bit of noise" minutes before the 7.8 midnight jolt.
Such claims go right back to Greece in 373BC, when weasels, snakes and centipedes reportedly left their homes and headed for safety several days before a destructive earthquake.
German scientists who have just published the first rigorous analysis of the so-called phenomenon collected reports on potential earthquake predictions across a variety of animals, from elephants to silkworms.
Most reports were anecdotes rather than experimental studies, and the majority of the reports came from three events: the 2010 Darfield earthquake that later led to the 2011 Christchurch Earthquake; the 1984 Nagano-ken Seibu earthquake in Japan; and the 2009 L'Aquila earthquake in Italy.
Writing in the Bulletin of the Seismological Society of America, a team from the GFZ German Research Centre for Geosciences explained most of these single observations and anecdotes could not be tested rigorously.
They suggest a series of questions that researchers should use in analysing the evidence that abnormal animal behaviour predicts earthquakes.
Lead author Dr Heiko Woith said scientists had to determine whether the link between the animal behaviuor and the earthquake is based on clearly defined rules - such as the animal's distance from earthquakes of a certain magnitude - and whether the animal behaviour had ever been observed and not followed by an earthquake.
Also required was a statistical testing hypothesis in place to examine the evidence, and whether the animal population is a healthy, among other questions.
These questions were rarely asked, making it difficult to systematically analyse the evidence for animal prediction, the researchers concluded after studying 729 reports of abnormal animal behavior related to 160 earthquakes.
"Many review papers on the potential of animals as earthquake precursors exist, but to the best of our knowledge, this is the first time that a statistical approach was used to evaluate the data," Woith said.
The reported unusual behaviours occurred anywhere from seconds to months prior to the earthquakes, and at distances from a few to hundreds of kilometers from the earthquake origins.
2010's Darfield Earthquake is one of the three events to have generated the most reports of animals behaving strangely before big quakes. Photo / File
Only 14 of the reports record a series of observations of the animals over time - most reports are single observations.
These weaknesses in the data make it difficult to confirm that these behaviors are predictive - meaning they signal an earthquake event before the event begins - rather than random occurrences or behaviours linked to the initial stages of an earthquake, such as foreshocks.
Foreshocks and abnormal animal behaviour strongly clustered together in the statistical analysis by Woith and colleagues, suggesting that at least some of the behaviours may be related to physical phenomena from a seismic event already underway.
"The animals may sense seismic waves - it could P, S or surface waves - generated by foreshocks," Woith suggested.
"Another option could be secondary effects triggered by the foreshocks, like changes in groundwater or release of gases from the ground which might be sensed by the animals.
"One of the biggest problems with the animal data, Woith said, is the lack of continuous, long-term observations of animals experiencing earthquakes.
"Up to now, only very few time series with animal behavior exist at all, the longest being just one year.
"Without a long record, Woith said, researchers cannot be sure that their observations relate to an earthquake and not some other kind of environmental change or long-term fluctuation in the health of an animal population or its predators.
The study follows another US paper that suggested something else strange might be able to predict natural disasters: tidal cycles, which was even linked to Mt Ruapehu's surprise eruption in 2007.
But New Zealand scientists cast serious doubt over that idea and criticised the methodology used for the study, which was recently published in a top international scientific journal.
