(ZOO ANIMALS/EARTHQUAKE) NORTHEAST UNITED STATES — 15 minutes before the largest earthquake the east coast has felt in 67 years, the animals of the Washington National Zoo were raising their alarm. Ducks, flamingos, orangutans, and other animals with an acute sense of their surroundings huddled together, dashed for safety, and let out warning calls. Though the quake was faint and only recorded with a magnitude of 5.8, tremors were felt and these animals were the first on the scene. Read on to learn how these animals sensed what was coming. — Global Animal
The Washington Post
The belief that strange animal behavior is a precursor to earthquakes goes back to antiquity. A recent scientific study suggested that toads fled to higher ground days before the 2009 earthquake in L’Aquila, Italy. In the most famous case of modern times, snakes and frogs emerged from their holes in 1975 in the dead of winter several weeks before a magnitude-7.3 earthquake in Haicheng, China (the odd animal behavior helped persuade officials to evacuate the city just before the tremor).
But scientists have struggled to convert anecdotal evidence into testable hypotheses and robust conclusions that can be published in peer-reviewed journals. Even the Haicheng case is squishy, because there were numerous foreshocks that may have rattled the snakes and inspired the public officials to take action.
Susan Hough, a U.S. Geological Survey seismologist who has researched earthquake predictions, said the simplest explanation for what happened at the zoo on Tuesday involves what scientists call the P wave.
An earthquake generates two types of seismic waves. The first is the relatively weak, fast-moving P wave, or primary wave. Then comes the more powerful S wave, or secondary wave, which lumbers along at a leisurely pace and heaves the ground up and down.
A back-of-the-envelope calculation by Hough suggests that the first P waves would have reached Washington about 15 seconds before the S waves. That may explain a lot: Iris and the other animals may have been responding to the P waves before humans noticed the ground shaking.
That leaves the mystery of the red-ruffed lemurs. They began hollering about 15 minutes — not seconds — before the earthquake. But that could be a coincidence, an outcry unrelated to the temblor. Hindsight can be misleading, as selective memory creates illusions of cause and effect.
All this remains an unresolved issue, and the possibility that animals are sensitive to terrestrial phenomena not discovered by humans can’t be ruled out.
As Hough put it, “There’s more going on in the Earth than we understand.”