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In order to reduce the risk of an earthquake and reduce and mitigate its effects, it is necessary to predict where and when a future, large earthquake may occur. For example, it would be important to know when such an earthquake will hit, where it will strike, and what the level of its destructiveness may be. Earthquake prediction at the present time is not an exact science, and forecasts of earthquake occurrences have not been very accurate. Presently predictions are given in statistical terms. For example, when a prediction is made that :here is a 90% chance that an earthquake will occur in the next 50 years", it does not mean that this earthquake cannot happen tomorrow or it may not be delayed by 50 years. Thus, present predictions are not within a reasonable time frame that can be of usefulness to planners, policy makers, and those in government that deal with public safety.
Unusual behaviour of animals prior to earthquakes received wide publicity after the Haichang earthquake of February 4, 1975 was successfully predicted in China. The official report was presented by the Chinese delegation at the Inter-governmental meeting convened at UNESCO, Paris in February 1976 which stimulated considerable scientific interest. Prior to this, however, several instances of abnormal animal behaviour were noticed before occurrence of some of the damaging earthquakes in different parts of the world, but they were considered more as historical legend. In Japan, innumerable rats were seen every day in a restaurant in Nagoya city, which suddenly disappeared on the evening prior to the Nobi earthquake of 1891.
Since the beginning of recorded history, observations of unusual animal behavior before earthquakes have been recorded by people from almost all civilizations. The animal behavior reports are often ambiguous and not consistently observed. In folklore, some animals have had more reports of being able to predict earthquakes than others, especially dogs, cats, chickens, horses, and other smaller animals. There have been reports with elephants, as well. Goats, cows, and most larger animals are generally reported as being less able to predict earthquakes.
In 1920, the largest earthquake to hit China with a magnitude of 8.5 occurred in Haiyuan County, Ninghxia Province. According to reports of eyewitnesses, prior to this earthquake, wolves were seen running around in packs, dogs were barking unusually, and sparrows were flying around wildly. It is reported that prior to the 6.8 magnitude earthquake in 1966 in Hsingtai County, Hopei Province, in Northern China, all the dogs at a village near the epicenter had deserted their kennels and thus survived the disaster.
The earliest reference we have to unusual animal behavior prior to a significant earthquake is from Greece in 373 BC.
As early as 1886, a seismologist named Milne had mentioned that dogs escaped from the city of Talcahuano in Chile before an earthquake (1835). Flocks of birds flew inland before the Chilean earthquakes of 1822 and 1835. Monkeys were reported to have become restless a few hours before the Managua earthquake (1972) in Nicaragua. In the Tientsin region of China, chickens refused to enter their dens, tigers became restless, yaks declined to eat and horses and sheep started running restlessly a few hours before the earthquakes of July 18, 1969. Hens and cocks were reported restless about an hour prior to the 1896 Ryukyu earthquake in Japan. In Yugoslavia, birds in zoo started crying before the 1963 earthquake. Deer gathered and cats disappeared from villages in northern Italy two or three hours before a damaging earthquake occurred in 1976. Such observations have also been noticed among animals who live underground, like snakes, insects and worms, and those living in water (fishes).
In Japan, fishes were reported to have disappeared before the Kanto earthquakes of 1923. Just before the 1855 Edo earthquake on November 11, many grass snakes were reported to have come out of the ground near the epicentral area, despite severe cold. Other instances involving fishes have been reported in Japan near north-western coast before the 1896 earthquake and the Tango earthquake of 1927 when abundant fishes were caught near the coast.
An interesting instance of unusual behaviour of dogs (but not of other animals) was reported before the destructive earthquake on November 24, 1976 in Turkey (Toksoz,1979).
Although several destructive earthquakes have occurred in the Himalayan region and elsewhere only one authentic observation of unusual animal behaviour was reported in India. In Govindpur in Jharkhand state of India, on February 19, 1892, animals were noticed to sniff the ground and exhibit nervousness such as dog shows in the presence of an unaccustomed object, while the air had distinctly sulphurous smell an hour before the shock.
During the recent damaging earthquakes in India of Uttarkashi (1991), Latur (1993), Jabalpur (1997), Chamoli (1999) and Bhuj (2001), there were reports of isolated cases of unusual behaviour of pet dogs, but the phenomenon was not observed on a large scale. According to the Chief conservator of forests for the Indian state of Tamil Nadu, a few minutes before the killer tsunami waves generated by an underwater earthquake hit the Indian coastline in December 2004, a herd of 500 blackbucks rushed away from the coastal areas to the safety of a nearby hilltop.
The Group of Earthquakes Research of the Institute of Biophysics, China (1979) carried extensive survey of the animal behaviour before damaging earthquakes occur. Its results are summarized below.
1. Most animals show increased restlessness before an earthquake.
2. The precursor time varies from a few minutes to several days, with increased restlessness at 11 hours which becomes still more marked about 2 to 3 hours before the earthquake. In general, the precursor times of various animals are mostly within 24 hours before the earthquake.
3. These observations have been noticed predominantly in the high intensity or epicentral regions close to active faults.
4. Changes in animal behaviour are observed during earth- quakes of magnitude 5 or more.
5. More intense responses can be noticed with the increase of intensity of earthquakes.
We can easily explain the cause of unusual animal behavior seconds before humans feel an earthquake. Very few humans notice the smaller P wave that travels the fastest from the earthquake source and arrives before the larger S wave. But many animals with more keen senses are able to feel the P wave seconds before the S wave arrives. As for sensing an impending earthquake days or weeks before it occurs, that's a different story.
There is little evidence for animals being able to sense earthquakes before they happen, although it is likely they can sense the initial, weaker P-wave or ultrasonic wave generated by a big underground explosion or the rupture of an earthquake, even if the waves are too small for humans' senses. These waves travel faster than the S-wave and Rayleigh earthquake waves that most strongly shake the ground and causes the most damage. It is speculated that when this happens, animals can detect the incoming earthquake wave, and start behaving agitatedly or nervously.
Others postulate that the animal behavior is simply their response to an increase in low-frequency electromagnetic signals. The University of Colorado has demonstrated that electromagnetic activity can be generated by the fracturing of crystalline rock. Such activity occurs in fault lines before earthquakes. According to one study, electromagnetic sensors yield statistically valid results in predicting earthquakes.
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.
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.
Srivastava, H.N., 1983.Earthquakes. National Book Trust, India.
Toksoz, M.N. 1979. Field investigations of the 24 November 1976 earthquakes in Turkey and its precursors. Int. Symp. Eathq. Pred. (UNESCO, Paris), Abstracts.