Monday, December 17, 2012

How to hear an Earthquake

The last two earthquakes I have experienced in Japan have been preceded by a low rumble (best described as a huge truck driving up towards our house - which is impossible because where we live has no access for trucks) approximately 1 minute before the earthquake occurs. 

I thought something was wrong with my ears but when I talked to another friend she had experienced the same thing and went to see a doctor who told her it was a phenomenon of very sensitive ears.

Both times it has happened I have warned my wife. 

It made me think of animals who, more attuned to nature than us, seem to have an awareness of the "hum" in nature and danger approaching, before it actually hits them. So birds fly away, dogs desert particular areas and so on.

I researched some scientific articles on the fact and discovered...

REVIEWS OF GEOPHYSICS, VOL. 19, NO. 2, PP. 247-270, 1981
Unusual animal behavior before earthquakes: A review of possible sensory mechanisms
Ruth E. Buskirk
Department of Psychiatry and Behavioral Sciences, University of Texas Medical Branch, Galveston, Texas, 77550
Cliff Frohlich
University of Texas at Austin, Marine Science Institute, Galveston, Texas 77550
Gary V. Latham
University of Texas at Austin, Marine Science Institute, Galveston, Texas 77550
To determine whether reports of unusual animal behavior before earthquakes are plausible, we have compared these reports with recent laboratory studies of animal sensory thresholds. Our major conclusion is that some animals are much more capable than humans of perceiving certain kinds of geophysical stimuli which may precede earthquakes. These geophysical stimuli are seismic or acoustic waves at low frequency (below 50 Hz), electric field changes, and olfactory stimuli. For example, recent studies suggest that some birds and fish are more sensitive than humans to sounds with frequencies below 40 Hz, and many animals are exceptionally good at perceiving low-frequency vibrations through their skin. 

Can Animals Sense Earthquakes?

Maryann Mott
for National Geographic News
November 11, 2003
The belief that animals can predict earthquakes has been around for centuries.
In 373 B.C., historians recorded that animals, including rats, snakes and weasels, deserted the Greek city of Helice in droves just days before a quake devastated the place.
Accounts of similar animal anticipation of earthquakes have surfaced across the centuries since. Catfish moving violently, chickens that stop laying eggs and bees leaving their hive in a panic have been reported. Countless pet owners claimed to have witnessed their cats and dogs acting strangely before the ground shook—barking or whining for no apparent reason, or showing signs of nervousness and restlessness.
But precisely what animals sense, if they feel anything at all, is a mystery. One theory is that wild and domestic creatures feel the Earth vibrate before humans. Other ideas suggest they detect electrical changes in the air or gas released from the Earth.
Earthquakes are a sudden phenomenon. Seismologists have no way of knowing exactly when or where the next one will hit. An estimated 500,000 detectable quakes occur in the world each year. Of those, 100,000 can be felt by humans, and 100 cause damage.
One of the world's most earthquake-prone countries is Japan, where devastation has taken countless lives and caused enormous damage to property. Researchers there have long studied animals in hopes of discovering what they hear or feel before the Earth shakes in order to use that sense as a prediction tool.
American seismologists, on the other hand, are skeptical. Even though there have been documented cases of strange animal behavior prior to earthquakes, the United States Geological Survey, a government agency that provides scientific information about the Earth, says a reproducible connection between a specific behavior and the occurrence of a quake has never been made.
"What we're faced with is a lot of anecdotes," said Andy Michael, a geophysicist at USGS. "Animals react to so many things—being hungry, defending their territories, mating, predators—so it's hard to have a controlled study to get that advanced warning signal."
In the 1970s, a few studies on animal prediction were done by the USGS "but nothing concrete came out of it," said Michael. Since that time the agency has made no further investigations into the theory.
Erratic Behavior in Dogs
Researchers around the world continue to pursue the idea, however. In September 2003 a medical doctor in Japan made headlines with a study that indicated erratic behavior in dogs, such as excessive barking or biting, could be used to forecast quakes.
There have also been examples where authorities have forecast successfully a major earthquake, based in part on the observation of the strange antics of animals. For example, in 1975 Chinese officials ordered the evacuation of Haicheng, a city with one million people, just days before a 7.3-magnitude quake. Only a small portion of the population was hurt or killed. If the city had not been evacuated, it is estimated that the number of fatalities and injuries could have exceeded 150,000.
The Haicheng incident is what gave people hope that earthquakes might be predictable, says Michael, and what prompted the animal behavior studies by the USGS.
It was later discovered, though, that a rare series of small tremors, called foreshocks, occurred before the large quake hit the city.
"It was the foreshock sequence that gave (Chinese officials) the solid prediction," Michael said.
Still, the Chinese have continued to look at animal behavior as an aid to earthquake prediction. They have had several notable successes and also a few false alarms, said Rupert Sheldrake, a biologist and author of the books, Dogs that Know When Their Owners Are Coming Home and The Sense of Being Stared At.
A reproducible connection between animal behavior and earthquakes could be made, he said, but "as the Chinese have discovered, not all earthquakes cause unusual animal behavior while others do. Only through research could we find out why there might be such differences."
Sheldrake did his own study looking at animal reactions before major tremors, including the Northridge, California, quake in 1994, and the Greek and Turkish quakes in 1999.
In all cases, he said, there were reports of peculiar behavior beforehand, including dogs howling in the night mysteriously, caged birds becoming restless, and nervous cats hiding.
Geologists, however, dismiss these kinds of reports, saying it's "the psychological focusing effect," where people remember strange behaviors only after an earthquake or other catastrophe has taken place. If nothing had happened, they contend, people would not have remembered the strange behavior.
Reporting Strange Behavior
Sheldrake disagrees. Comparable patterns of animal behavior prior to earthquakes have been reported independently by people all over the world, he said. "I cannot believe that they could all have made up such similar stories or that they all suffered from tricks of memory."
More research is needed and is long overdue, said Sheldrake, who proposes a special hotline or Web site where people could call or write in if they saw strange behavior in their animals. A computer would then analyze the incoming messages to determine where they originated. A sudden surge of calls or e-mails from a particular region might indicate that a quake was imminent.
The information would be checked to make sure the observations were not caused by other circumstances known to affect the behavior of animals, such as fireworks, or changes in weather. And to avoid issuing false warnings, Sheldrake said, the data would be used in conjunction with other monitoring devices such as seismological measurements.
"Such a project would capture the imagination of millions of people, encourage large-scale public participation and research—and would be fun," he said. "What is holding this research back is not money but dogmatism and narrow-mindedness.

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