Earthquake prediction

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Image:Eq-prob.jpg An earthquake prediction is a prediction that an earthquake of a specific magnitude will occur at a specific location and time. Seismologists are not currently able to predict earthquakes with such accuracy, instead they focus on calculating the seismic hazards of a region and the probabilities that a given earthquake will occur.

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Controversy in trying to predict earthquakes

With regard to predictive seismology, humans have tried to associate an impending earthquake with such things as animal behavior, electromagnetic fields, weather conditions, unusual clouds, radon gas in ground water, water level in wells and so on - thereby suggesting that the dataset of observed seismicity is dependent on a large number of external variables.

Controversy arises as a result, since conclusions usually should not be made from a small data set unless a well understood physical phenomenon is present, particuarly when the data set is noisy or there are questions regarding how it is gathered.

There is, however, one interesting experiment about to get under way by a graduate researcher at California State University, East Bay. It is called The Earthquake Weather Project, a web-based system which will attempt to gather and analyze data based on some of the more commonly held beliefs mentioned above, no doubt adding to the controversy surrounding earthquake prediction.

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Parkfield, California

Some types of earthquake predictions do not have to be ultra precise in magnitude, time and place to be socially useful. Predictions of a general nature can be quite useful if they are based on scientific principles.

For example, the region near the town of Parkfield in California has experienced a magnitude 6 earthquake approximately every 22 years since 1857. This led researchers to predict that a similar quake would hit the region between 1988 and 1992. As a result of this prediction, the area around Parkfield was heavily instrumented with monitoring equipment in order to record this event and researchers hoped any data collected would help in unlocking the secret of predicting future earthquakes.

However, the predicted earthquake failed to materialize on the expected fault, though a sizable quake did occur in nearby Coalinga, California in 1983. Some researchers believe the Coalinga quake may have released some of the stress on the San Andreas Fault near Parkfield, and was a substitute for the missing quake.

If that was the case, then one would have expected that the next quake in the Parkfield region would be sometime in the mid 2000s. Another earthquake did in fact occur near Parkfield, this time in San Simeon, California in December 2003, but like the Coalinga earthquake in 1983, this quake was also not located on the San Andreas Fault. Regrettably, two fatalities were recorded in the town of Paso Robles as a result of structure failure during the shaking.

On September 28, 2004, the expected Parkfield earthquake finally occurred. However, data returned has not yielded as much information as researchers had hoped.

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Earthquake Prediction in China

Chinese earthquake prediction research is largely based on unusual events before earthquakes, such as change of ground water levels, strange animal behavior and foreshocks. They successfully predicted the February 4, 1975 M7.3 Haicheng Earthquake[1], and the China State Seismological Bureau ordered an evacuation of 1 million people the day before the earthquake, but failed to predict the July 28, 1976 M7.8 Tangshan earthquake[2]. This failure put Chinese earthquake prediction research in doubt for several years.

Chinese research has now merged with western research, but traditional techniques are still common. Another successful prediction of the November 29, 1999, M5.4 Gushan-Pianling Earthquake in Haicheng city and Xiuyan city, Liaoning Province, China was made a week before the earthquake. No fatalities or injuries were reported. (People's Daily, [3])

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Animal behavior

Some people believe that there is evidence that animals sense the immediate onset of earthquakes. In support of this claim instances are cited when people have witnessed flight of animals just before an earthquake disaster. In fact, according to the Chief conservator of forests for Tamilnadu, a few minutes before the killer tsunami waves generated by an underwater earthquake hit the Indian coastline in December 2004, a 500 strong herd of blackbucks rushed away from the coastal areas to the safety of a nearby hilltop. Since the beginning of recorded history, observations of unusual animal behavior before earthquakes have been recorded by people from almost all civilizations. The Chinese began a systematic study of this unusual animal behavior and in December 1974 predicted a major earthquake that did, in fact, occur in February 1975. But skeptics claim to debunk nearly all such observations. According to them these reports are often ambiguous. They cite several instances when no changes in any animal behavior were reported. According to them although some animals do behave abnormally prior to an earthquake this does not happen always. More detailed observations are required before any conclusions can be drawn. Some animals have had more reports of being able to predict quakes than others. Likely: Dogs, cats, chickens and other smaller animals. There have been reports with elephants, too. Unlikely: Goats, horses, cows, and larger animals.

There is a man in southern California who keeps track of missing cats and dogs reported in his local newspaper. Approxametly 7.5 times more animals go missing about a week before a major earthquake. This man has issued earthquake warnings based on this with about 75% accuracy.

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Other predictions

In early 2004, a group of scientists at the University of California, Los Angeles, lead by Dr. Vladimir Keilis-Borok, predicted that a quake similar in strength to the San Simeon earthquake would occur in a 12,000 square mile (31,100 km) area of Southern California by September of that year.

In April 2004, the California State Office of Emergency Services formally endorsed the prediction made by Kellis-Borok that there would be a strong earthquake in the Southern California region. The expected earthquake never occurred.

Based on the historic record of the various published efforts to predict a quake, it might be easy to conclude that earthquake prediction is usually an imprecise, but nonetheless scientifically and socially useful art.

According to new research to be published by Prof. Shlomo Havlin, of Bar-Ilan University's Department of Physics, earthquakes form patterns which can improve the ability to predict the timing of their recurrence. In November 2005 (Nov 11 issue) the journal Physical Review Letters, published by the American Physical Society, published an article by researches from Israel and Germany that say that there is a way to predict when the next earthquake will hit.

Prof. Shlomi Havlin's from Bar-Ilan University in Israel, in collaboration with Prof. Armin Bunde, of the Justus-Liebig University in Giessen, Germany, and Bar-Ilan University graduate student Valerie Livina used the "scaling" approach from physics to develop a mathematical function to characterize earthquakes of a wide range of magnitudes in order to learn from smaller magnitude earthquakes about larger magnitude earthquakes. The team's findings reveal that the recurrence of earthquakes is strongly dependent on the recurrence times of previous earthquakes.

This memory effect not only provides a clue to understanding the observed clustering of earthquakes, but also suggests that delays in earthquake occurrences, as seen today in Tokyo and in San Francisco, are a natural phenomenon.

In another paper in the journal Nature (November 9 issue, [4]), Richard Allen of the University of California claims that the distinction between small and large earthquakes can be made from the very first second of information, though other scientists are not convinced.

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See also

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External links

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