Earthquake prediction: Difference between revisions

Seismic hazard map of the San Francisco Bay Area, showing the probability of a major earthquake occurring by 2032

An earthquake prediction is a prediction that an earthquake in a specific magnitude range will occur in a specific region and time window. Seismologists are not currently able to predict earthquakes with such accuracy, though the early results of the Demeter satellite suggest that this could become possible; instead they focus on calculating the seismic hazards of a region by estimating the probabilities that a given earthquake or suite of earthquakes will occur.

Controversy in trying to predict earthquakes

With regard to earthquake prediction, people have tried to associate an impending earthquake with such potential precursors as seismicity patterns, electromagnetic fields, weather conditions and unusual clouds, radon or hydrogen gas content of soil or ground water, water level in wells, animal behavior, and so on - thereby hoping that the observed seismicity foreshadows its destruction by such observable phenomena.

Thus far, controversy has arisen because most conclusions have been made from a small data set, sometimes without well-understood physical phenomenon in mind to explain the claims. This is particularly a problem when the data set is noisy or there are questions regarding how it is gathered.

A meaningful earthquake prediction must have all the following elements:

• Specific area
• Specific magnitude or magnitude range
• Specific time window
• Estimate of probability compared to random chance
• A physical basis

A meaningful 'forecast' does not require the same accuracy, it simply includes a vague suggestion of timing and location of events (eg. the Tokyo Earthquake is expected every 80 years, this is a forecast, not a prediction)

Tidal forces

Historically, 60% of major earthquakes (magnitude 7 or greater) occur during the 14% of the year when the tidal forces are near their maximum. For maximum tidal force, three factors must coincide: First, when the moon (in its elliptical orbit) is closest to the earth; second, when it is within a day or two of a new moon (so that the tidal forces of the moon and sun are acting in concert); and third, when the earth (in its elliptical orbit) is at or near its closest distance to the sun.

In 2007, these dates are January 19-23, February 16-20, and March 17-21. We should expect that during at least two of these three time periods a major earthquake, possibly accompanied by a major volcanic eruption, will occur. April 15-19 and May 14-18 also are susceptible periods for major earthquakes in 2007, although the earth has by that time moved further from the sun.

(Note: This section on Tidal Forces was first submitted to Wikipedia on January 16, 2007. There already has been confirmation of the first predicted tidal-related major earthquake: the U.S. Geological Survey reports that on January 22, 2007 there was a magnitude 7.3 earthquake in northeastern Indonesia.)

Please also note that the above prediction covers a total of about 20 days for 2007, or about 5% of the year. On average, about 10 M>7 earthquakes occur somewhere in the world every year. Thus there is a roughly 50% probability that one of these earthquakes will occur within one of the prediction windows listed above.

There have been a number of statistical studies that have tried to connect tidal forces and earthquake occurrence, with little success. The exception is that there may be some weak tidal triggering of shallow, oceanic thrust-faulting earthquakes

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 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. 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.

Demeter microsatellite

The CNES satellite has made observations which show strong correlations between certain types of low frequency electromagnetic activity and the seismically most active zones on the Earth, and have shown a sharp signal in the ionospheric electron density and temperature near southern Japan seven days before a 7.1 magnitude occurred there (on August 29 and September 5, 2004, respectively).

Animal behavior

Animals can detect the 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 Love and Rayleigh earthquake waves that most strongly shake the ground and causes the most damage. 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 recent research, electromagnetic sensors yield statistically valid results in predicting earthquakes — modern science's answer to centuries of human observation of animals.

Some people believe that in these ways, 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 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 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. In fact, the 1975 prediction relied most heavily on a series of strong foreshocks. The animal behavior reports are often ambiguous and not consistently observed. There is little evidence for animals being able to sense impending earthquakes, although it is likely they can sense the initial, weaker P-waves before people. Seismometers remain much more sensitive than even the animals, however.

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.

Japan has a long tradition associating catfish with earthquake prediction. From this idea emerged a long university research programme concluding in 2004 in which it was proposed that the (established) high sensitivity of catfish to electric fields was involved in detecting fields of a few hertz because of piezoelectric effects on deeply buried quartz crystals. Actual monitoring of catfish and correlation with earthquakes gave results that are not promising.

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. The odds were given as 50/50.

In April 2004, the California Earthquake Predicition Evaluation Council (CEPEC) evaluated Keilis-Borok's prediction and reported to the California State Office of Emergency Services. CEPEC concluded that the "uncertainty along with the large geographic area included in the prediction (about 12,400 square miles) leads (us) to conclude that the results do not at this time warrant any special policy actions in California.” The predicted time window came and went with no significant earthquake.

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

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 researchers 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, Richard Allen of the University of California claims that the distinction between small and large earthquakes can be made from the very first seconds of seismic energy recorded by seismometers, though other scientists are not convinced. If correct this may make earthquake early warning (as distinct from prediction) more powerful. Earthquake early warning provides an alarm that strong shaking is due soon to arrive, and the more quickly that the magnitude of an earthquake can be estimated, the more useful is the early warning.

Loma Prieta, California

From 1968 to 1988 scientists in California mapped seismic activity on a cross section of the fault lines. They identified a "seismic gap" in the Loma Prieta area from various features of the regional seismicity. They therefore concluded that Loma Prieta was due for an earthquake. On 17 October 1989 the Loma Prieta earthquake occurred, initially reported as measuring 7.1 on the Richter scale but later more accurately recorded as moment magnitude 6.9, causing 63 deaths. This prediction, however was not very useful as it could not predict the exact date.

See also

• Forecasting
• Earthquake storm
• Earthquake weather
• Earthquake warning system
• Jim Berkland (and the role of the moon)

External links

• The USGS view on earthquake prediction http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/eq_prediction.html
• Studies on Tide-Forming Forces and Earthquakes were published in 1967 and 1968 by Elsevier, but the U.S. Geological Survey: Common Myths About Earthquakes contradicts this study.
• PetQuake - Encourages users to submit reports of atypical animal behavior and produces real-time dot map of the United States
• When Will the Next Earthquake Occur?
• Stopping the next big one - Is Earthquake prediction and prevention possible?
• Earthquake Predictions
• The Earthquake Weather Project
• Earthquake Prediction - Updated Daily