Part of a series on earthquakes |
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Types |
Foreshock • Aftershock • Blind thrust Doublet • Interplate • Intraplate Megathrust • Remotely triggered • Slow Submarine • Supershear Tsunami • Earthquake swarm |
Causes |
Fault movement • Volcanism • Induced seismicity |
Characteristics |
Epicenter • Hypocenter • Shadow zone Seismic wave • P-wave • S-wave |
Measurement |
Mercalli scale • Richter scale Moment scale • Surface wave magnitude scale Body wave magnitude scale • Seismometer Earthquake duration magnitude |
Prediction |
Coordinating Committee for Earthquake Prediction Earthquake sensitive |
Other |
Shear wave splitting • Adams–Williamson equation Flinn-Engdahl regions • Earthquake engineering Seismite • Seismology |
An earthquake prediction is a prediction that an earthquake of a specific magnitude will occur in a particular place at a particular time (or ranges thereof). Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month.[1] However, for well-understood faults the probability that a segment may rupture during the next few decades can be estimated.[2]
Scientists still do not know many of the details of the physical processes involved in earthquakes and how to predict them. The theory of plate tectonics was born in the mid 1960s and confirmed in the early 1970s. Many phenomena are considered to be possible precursors of earthquakes, and among those under investigation are seismicity, changes in the ionosphere, various types of electromagnetic indicators including infrared and radio waves, radon emissions, and even unusual animal behavior.
According to the Seismological Society of America, for a statement to be accepted as a valid earthquake prediction, it has to contain the expected magnitude with error limits, the well defined area of the epicenter, the range of dates, and the probability of this to come true. The data from which the prediction was derived must be verifiable and the analysis of these data must be reproducible. Long term predictions (years to decades) are more likely to be achieved than medium term predictions (months to years), and short term predictions (hours to days) are in general unlikely to be possible, at present. If a plausible mechanism linking the observations with the predicted earthquake is not offered, the credibility of the prediction is diminished, but it may not necessarily be rejected. Evaluations of apparent successes must include a statistical estimate of the probability that the prediction came true by chance, which is often the case with predictions by amateurs. Whether a prediction is scientific or amateurish is not based on who makes the prediction, but based on how the prediction is made and tested. Predictions can be formulated either by defining the limits of the parameters probabilistically or by firm values.
In efforts to predict earthquakes, seismologists have investigated the association of an impending earthquake with such varied phenomena as seismicity patterns,[3][4][5][6][7][8] crustal movements,[9][10] ground water level in wells,[11] radon or hydrogen gas emissions from the Earth,[12][13] changes of seismic wave velocities,[14] electromagnetic fields (seismo-electromagnetics),[15] large-scale changes in soil temperature,[16] and changes in ion concentration in the ionosphere.[16] "Earthquake prediction: An overview" is a 2003 review by Hiroo Kanamori[17] and the August 2010 issue of Pure and Applied Geophysics contains a collection of articles on the subject.[18]
The mystery of earthquake occurrence frequently sparks people without scientific training into claiming that they have found the solution to the earthquake prediction problem. Discredited, fantastic theories of predicting earthquakes include weather conditions and unusual clouds, and the phases of the moon.[19] These pseudoscientific theories and predictions[20] ignore the requirement of rigorously formulating the hypothesis and to test it statistically.[1]
Self-appointed prediction experts often resort to the technique of making vague statements, which they claim were correct predictions, after an earthquake has happened somewhere.[21] Rudolf Falb's "lunisolar flood theory" is a typical example from the late 19th century.
In the United States an earthquake prediction program was formulated in the mid 1960s[22] and began to hold, jointly with Japan, earthquake prediction conferences, but there existed no serious research effort in the USA until 1977, when the National Earthquake Hazards Reduction Program was initiated.[23] Part of its original mandate was the development of earthquake prediction techniques and early-warning systems.[24] However, the emphasis was shifted away from earthquake prediction in 1990, and toward mitigation of the damage, due to legislation co-sponsored by Senator Al Gore.[25] In 1984, the Parkfield Prediction Experiment was launched.[26] It failed to correctly predict the characteristic Parkfield earthquake on the San Andreas fault.[27] In 1995, the National Academy of Sciences sponsored a colloquium, "Earthquake Prediction: The Scientific Challenge," which did not bring much new information about prediction.[28]
In Japan, an earthquake prediction program was started in 1964[29] and a subsequent five-year plan was formulated by Rikitake.[30] This program became focused in 1978 on predicting a magnitude 8 earthquake in the Tokai district, near Tokyo, which may become a major disaster for Japan, and the world economy, once it happens. Japan is now the best instrumented country in the world for recording seismic waves, crustal deformation, properties of ground water, and electro-magnetic transients,[31] all as part of a massive effort to try to understand the earthquake generation process.
In China, it is the job of governmental seismological agencies to coordinate the research and its application to earthquake prediction. In 1956, China included earthquake prediction research as an important task in the 12-year national long-term plan for science and technology development (1956–1967).[29] The State Seismological Bureau (SSB), now named the China Earthquake Administration (CEA), was established in 1970. The CEA is a governmental body responsible to the State Council, and required by the ‘‘Law of the People’s Republic of China on Protecting Against and Mitigating Earthquake Disasters’ to conduct Annual Consultation Meetings on Earthquake Prediction Research and Applications every January.[32][33][34] In 1975, people were evacuated before the magnitude 7.3 Haicheng earthquake.[35] This was claimed as a successful prediction, but was in fact a precautionary action initiated by leaders of the local government, reacting to hundreds of foreshocks, some of which damaged some buildings.[36] Since then, several disastrous earthquakes which have not been predicted have ravaged China.[37]
In Russia, the new program of development of earthquake prediction in Russia was designed by order of the President of the Russian Federation in 2004. It is targeted at increasing the reliability of long-, medium, and short-term forecasting of the earthquake potential, including tsunami prediction.[38]
The program comprises:
Seven test sites will be positioned in seismically active areas:
Four test sites will be positioned in areas with abnormal high-level technogenic burden:
The eleven new and modernized test sites will perform:
The main targets of the Coordination Center for Earthquake Prediction are:
Earthquake predictions and methods are reviewed by the Earthquake Forecast Advisory Council (FAC) of the Russian Academy of Sciences (RAN) and the Ministry of Emergency Situations of Russia (EMERCOM). Russia has an earthquake prediction program that has yielded some of the best tested hypotheses, but also some claims that are viewed with suspicion, internationally. Peter Bormann has presented a review of individual achievements and claims by Russian seismologists.[29]
The Collaboratory of the Study of Earthquake Predictability (CSEP) is an international multi-institution effort, underway since 2005, to develop a peer-reviewed scientific testing platform and expert community to assess earthquake prediction and predictability.
In 1969 Japanese seismologist Kiyoo Mogi proposed that there exists a precursory seismicity pattern before large earthquakes[39] that has become known as the 'Mogi doughnut hypothesis'. He showed maps that suggested that major earthquakes tend to occur in seismically unusually calm areas surrounded by a ring of unusually high seismic activity.[40][41][42] However, he did not back up his claim by statistical analyses that would have shown whether or not these patterns constituted a significant departure from normal.
Subsequently, several groups have separately tested with statistical methods the inside and the outside patterns. The idea that there sometimes exists a 'calm before the storm' is called the quiescence hypothesis,[43][44] the idea of precursory increased activity in the ring outside is called the accelerated seismic moment release hypothesis.[45][46]
The research regarding the use of these patterns for earthquake prediction is discussed in the following in separate sections because it is extensive and complex.
Emission of radon as a quake precursor was studied in the 1970s and 80s with no reliable results and continued to be dismissed by most seismologists until recently.
VAN is a controversial method of earthquake prediction proposed by Professors Varotsos, Alexopoulos and Nomicos in the 1980s; it was named after the researchers' initials. The method is based on the detection of "seismic electric signals" (SES) via a telemetric network of conductive metal rods inserted in the ground; it stems from theoretical predictions by P. Varotsos, a solid-state physicist at the National and Capodistrian University of Athens.[47] First, VAN have claimed to be able to predict earthquakes of magnitude larger than 2.8 within all of Greece with a precursor time of 7 hours. Later the claim changed to being able to predict earthquake larger than magnitude 5, within 100 km of epicentral location, within 0.7 units of magnitude, and in a 2-hour to 11-day time window, but this is disputed.
Errors have been discovered in the list of earthquakes correlated according to Van with SES signals. VAN has claimed to have observed at a recording station in Athens a perfect record of a one-to-one correlation between SESs and all earthquakes of magnitude ≥ 2.9 which occurred 7 hours later in Greece.[48] However, it was later shown that the list of earthquake used for the correlation was false. Although VAN stated in their article that the list of earthquakes was that of the Bulletin of the National Observatory of Athens [2] it was found that 37% of the earthquakes actually listed in the bulletin, including the largest one, were not in the list used by VAN for issuing their claim. In addition, 40% of the earthquakes which VAN claimed had occurred were not in the NOA bulletin.[49]
Objections have been raised that the physics of the claimed process is not possible. None of the earthquakes which Van claimed were preceded by SESs generated an SES themselves, which would have to be expected because the main shock disturbance in the Earth is much larger than any precursory disturbance. An analysis of the wave propagation properties of SESs in the Earth’s crust showed that it is impossible that signals with the amplitude reported by VAN could have been generated by small earthquakes and transmitted over the several hundred kilometers distances from the epicenter to the receiving station.[50][51]
Several authors have pointed out that VAN’s publications are characterized by a lack of addressing the problem of eliminating the many and strong sources of change in the magneto-electric field measured by them, such as currents generated near their recording station in suburban Athens, and especially by a lack of statistical testing of the validity of their hypothesis.[52][53][54][55] In particular, it was discovered that of the 22 claims of successful prediction by VAN[56] 74% were false, 9% correlated at random and for 14% the correlation was uncertain.[57]
Foreshocks are medium-sized earthquakes that precede major quakes.
An increase in foreshock activity[1] (combined with purported indications like ground water levels and strange animal behavior) enabled the successful evacuation of a million people one day before the February 4, 1975 M7.3 Haicheng earthquake[58]
The Xiuyan M5.3 earthquake (29 November 1999) is another example where a successful prediction was issued, based on a correct interpretation of an earthquake swarm as foreshocks.[59][60]
While 50% of major earthquakes are preceded by foreshocks, only about 5-10% of small earthquakes turn out to be foreshocks, leading to false warnings.[1][61][62]
There are two flavors of tidal stressing that have been claimed to generate enhanced rates of earthquakes—diurnal and biweekly Earth tides. The diurnal correlations would cause more earthquakes only during the hours when the tidal stress is pushing in an encouraging direction. In contrast, biweekly effects would be earthquakes occurring during the days when the sinusoidal stressing oscillations are largest. The former, as most easily observed in the twice-daily rise and fall of the ocean tides, have occasionally been shown to influence earthquakes (e.g., Cochran, Vidale and Tanaka (2004) shows there may be some weak tidal triggering of shallow, oceanic thrust-faulting earthquakes).[63] The latter, which arises from the periodic alignment of the Sun and Moon, has often been claimed in the popular press to incubate earthquakes (sometimes termed the "syzygy" effect) and occasionally for small datasets in the scientific literature (e.g., Glaser (2003)[64]), but generally such effects do not appear in careful studies of large datasets.
A paper written by researchers from Beijing Normal University and the Chinese Academy of Sciences found a significant relationship between tidal forces and earthquakes in China and Taiwan. The paper considered the relationship between 21 major earthquakes (Ms ≥ 7.0) in land and the offshore area of Taiwan island in the 20th century and the variance ratio of the lunar–solar tidal force. The result indicated that the time of these earthquakes is closely related to the variance ratio of the lunar–solar tidal force, and therefore that the tidal force possibly plays an important role in triggering earthquakes.[65] The conclusion is this method may be used to help forecast earthquakes by studying the lunar perigee.
Syzygy, which is not given much credence in the scientific community, is motivated by the observation that, historically, there have been some great earthquakes whose timing coincides with tidal forces 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.
Shallow earthquakes near mid-ocean ridges, volcanic earthquakes, and episodic tremor and slip have also been observed to sometimes correlate with the diurnal tides, with enhanced activity correlating with times that faults are unclamped.
An earthquake warning system is a system of accelerometers, communication, computers, and alarms that is devised for regional notification of a substantial earthquake while it is in progress. Japan, Taiwan and Mexico all have earthquake early-warning systems.
In a 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.[66] 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. However, earthquake early warning can still be effective without the ability to infer the magnitude of an earthquake in its initial second or two.
Official earthquake prediction evaluation councils have been established in California (the California Earthquake Prediction Evaluation Council) and the federal government in the United States (the National Earthquake Prediction Evaluation Council), but have yet to endorse any method of predicting quakes as reliable.[1]
Unless the following parameters are specified, a statement does not qualify as an earthquake prediction:[67]
The sub-commission for earthquake prediction of IASPEI (International Association of Seismology and Physics of the Earth’s Interior) has reviewed claims of successful predictions and of proposed methods to predict during the 1990s. Their procedure was similar to reviews of proposals for research grants. Authors submitted their detailed research on the prediction problem. Anonymous reviewers commented, and members of the sub-commission discussed the merits of the proposal and of the reviewer’s comments.
A decision to place the claim into one of three categories (preliminary list of significant precursors, no decision, rejected) was then transmitted to the authors, who could write a reply, if they so wished. The entire exchange was then published, unless the authors did not agree to publication.[68][69] Most of the nominated successful predictions and methods to predict were rejected.[70] At that time, three methods seemed most promising: Seismicity patterns, ground water properties, and crustal deformations.[71]
Attribution to a plausible physical mechanism lends credibility, and suggests a means for future improvement. Reproducibility and statistical analysis are used to distinguish predictions which come true due to random chance (of which a certain number are expected) versus those that have more useful predictive capability, and to validate models of long-term probability. Such models are difficult to test or validate because large earthquakes are so rare, and because earthquake activity is naturally clustered in space and time. "Predictions" which are made only after the fact are common but generally discounted.
Animal behavior reports are often ambiguous and not consistently observed. In folklore, some animals, especially dogs, cats, chickens, horses, toads and other smaller animals, have been identified as being more able to predict earthquakes than others.
It has been postulated that the reported animal behavior before an earthquake is simply their response to an increase in low-frequency electromagnetic signals.[72]
In Italy, findings from 2009 suggest that toads are able to detect pre-seismic cues.[73] In the 2011 Virginia earthquake, animals at the Smithsonian National Zoological Park were reported to have sensed the Earthquake coming.[74]
Earthquake prediction in the form of animal behavior can be dated as far back as 373 BC. It was believed that rats, weasels, snakes, and centipedes would flee their homes as early as a few days before a large earthquake. It is easy for us to explain how animals can predict earthquakes mere seconds before they occur, however their ability to predict earthquakes days before the occurrence is still debatable. Animals with more keen senses possess the ability to detect P waves that occur before the S waves, while humans simply cannot. We do understand that animals possess an instinctive response to stimuli in order to escape predators, and certain vertebrates have a sort of "early warning" behavior. It is possible that these instinctive responses and "early warning" behaviors could have evolved into something more: a system for evading seismic activity. [75]
American seismologists are very skeptical on this topic. Although documented cases of odd animal behavior directly before an earthquake, the United States Geological Survey states that there can be no reproducible connection between seismic activity and animal behavior. Andy Michael, a geophysicist at USGS says, "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 1970's, the USGS conducted experiments on animal behavior in relation to earthquake prediction, however "nothing concrete came out of it." said Michael. The USGS has done no further experiments on this topic. Geologists dismiss this theory for the reason of the "Psychological focusing effect", which essentially states that people will only remember these strange behaviors due to the earthquake, or any other major occurrence. If not for the earthquake, these odd behaviors in animals would not be noted. [76]
The largest earthquake to ever hit China occurred in Haiyuan County, Ninghsia Province, in 1920, with a magnitude of 8.5. Before the earthquake, eyewitnesses reported observing wolves running around in packs, sparrows flying wildly, as well as dogs barking in an unusual manner. In addition, prior to the 6.8 magnitude earthquake in Hsingtai County, Hopei Province of 1966, dogs in a village at the epicenter of the quake managed to escape their kennels and thus surviving the catastrophe. In 1969, a warning was issued at the Tientsin People's Park Zoo, just two hours before the earthquake struck. This warning was based upon odd behaviors in various animals in the zoo, including, but not limited to; giant pandas, deer, sharks, tigers, and yaks. Another report states that in 1976, a local stock breeder was tending to his animals, but instead of eating, the horses and mules were jumping and kicking furiously until they were able to break free and ran outside. Moments later, a 7.3 magnitude earthquake struck the area. [77]
One possible method for predicting earthquakes is fractoluminescence. Studies at the Chugoku National Industrial Research Institute by Yoshizo Kawaguchi have shown that upon fracturing, silica releases red and blue light for a period of about 100 milliseconds. Kawaguchi attributed this to the relaxation of the free bonds and unstable oxygen atoms that are left when the silicon oxygen bonds have broken due to the stresses within the rock.[78] It has not been applied yet only because of various limitations of current technology. First, blue light does not travel well through the ground,[79] which makes it necessary to place either transducers that turn a light signal into an electrical signal or fiber optic interfaces allowing a direct pick up of blue light into an optical medium in direct contact with the rock that is about to fracture, and to lay the corresponding optical or electrical transmission lines required for bringing the signal to the surface. Secondly, since the exact position where rocks are going to fracture is known only with a degree of approximation, a very large volume of rock [80] where fracture is reasonably expected to happen needs to be covered with transducers or optical interfaces. Thirdly, considering that most earthquakes are due to fractures taking place at depths of several kilometers, building the whole required infrastructure is still beyond the reach of current drilling technology.
The "Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions" satellite, constructed by CNES, has made observations which show strong correlations between certain types of low frequency electromagnetic activity and the most seismically 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).[81]
Quakesat is an earth observation nanosatellite based on 3 CubeSats. It was designed to be a proof-of-concept for collecting extremely low frequency earthquake precursor signals from space. The primary instrument is a magnetometer housed in a 2 foot (0.6 m) telescoping boom.
ESPERIA is an equatorial space mission mainly concerned with detecting any tectonic and preseismic related signals. More in general, it has been proposed for defining the near-Earth electromagnetic, plasma, and particle environment, and for studying perturbations and instabilities in the ionosphere-magnetosphere transition region. To study earthquake preparation processes and anthropogenic impacts in the Earth's surface, a phase A study has been realized for the Italian Space Agency.[82]
The Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) radar satellite, which was canceled in the White House's 2012 budget proposal, would have the capacity to identify elastic strain in tectonic plates, combining L-band interferometric synthetic aperture radar and a multi-beam infrared lidar to detect strains in the Earth’s surface that could lead to serious earthquakes.[83][84]
Russia and the United Kingdom have agreed to jointly deploy two satellites in 2015 that will measure electromagnetic signals that are released from the earth's crust prior to earthquakes. The project is said to be able to "help predict earthquakes and potentially save thousands of lives." [85]
After a series of foreshocks, some of which damaged buildings, local government leaders evacuated much of the populace before the devastating magnitude 7.3 1975 Haicheng earthquake. Although much discussion about the possibility of future earthquakes in NE China had taken place during the years preceding this earthquake, there was no prediction formulated that would have fit this event.[86]
However, the Chinese government failed to predict the July 28, 1976 M7.8 Tangshan earthquake, which put Chinese earthquake prediction research in doubt for several years. In the late 1990s, there were over thirty false alarms unofficially announced in China.[87]
On November 29, 1999 an earthquake of magnitude 5.3 [3] occurred at latitude 40.46 and longitude 122.89, near Xiuyan. On November 28, 1999, the Seismological Bureau of Liaoning Province (a branch of the China Seismological Bureau) issued a prediction with the following parameters.[60]
This means that the event was located only 10 km from the center of the specified area, occurred within the time window, and the magnitude range given. Thus, this was a correct prediction.[59]
The research activities, which lead to this prediction started on November 9 because two magnitude 4 earthquakes occurred. Another two magnitude 4 earthquakes occurred on November 25, and on November 26 a magnitude 4.4 earthquake triggered the report by seismologists to the local government, stating "if the earthquake swarm keeps increasing, then a 5.5-6.0 earthquake is imminent; otherwise there would be a M6 earthquake expected to occur, but location cannot be sure (based on present data and knowledge)".[60] The local government's decision was to deploy imminent works to enhance the preparedness, without issuing a prediction publicly. Because of this special deployment, there were no injuries and deaths during the earthquake, nor social panic before and after the earthquake.[59][60][88]
The Japanese government established the Imperial Earthquake Investigation Committee in 1892 in response to the Nobi (Mino-Owari) earthquake (1891) which caused significant damage in Japan.[89]
In the 1970s and 1980s, the Japanese government embarked on a major earthquake preparedness campaign, which some criticized as emphasizing prediction too much over mitigation.[90] It failed to result in a prediction of the Great Hanshin earthquake which devastated the city of Kobe in 1995. See also 2011 Tōhoku earthquake and tsunami.
An earthquake predicted by a scientist at the U.S. Bureau of Mines to occur on June 28, 1981, in Lima, Peru, failed to materialize. Despite being dismissed by the U.S. National Earthquake Prediction Evaluation Council, the prediction caused popular fear and many left the city.[91]
Based on a history of regularly spaced earthquakes in the early 20th century, the USGS in 1985 began an experiment based on the predictions and published papers of Allan Lindh and W.H. Bakun of the USGS and T.V. McEvilly of the University of California at Berkeley. The goal was to predict a 6.0 magnitude earthquake near Parkfield, California.[92]
"Bakun and Lindh summarized the state of the art in the Parkfield Prediction Experiment, and predicted that a moderate-size earthquake would occur at Parkfield between 1985 and 1993. Their prediction was unusual both in its precision (as to location, time and magnitude) and high degree of confidence (95% within the 9-year window). Bakun and Lindh (1985) also suggested that the predicted earthquake could produce extended rupture of the San Andreas fault to the southeast, possibly growing to magnitude 6.5 to 7.0."[93]
Media attention focused on the prediction and the experiment. 122,000 pamphlets were mailed to residents of the Parkfield area, entitled "The Parkfield Earthquake Prediction."[94] Despite the prediction, such an earthquake did not occur until after the end of the prediction window, in 2004.[1]
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. Smaller quakes several months beforehand were treated as possible foreshocks, but the warnings had expired by the date of the moment magnitude 6.9 quake, on 17 October 1989.[1]
Jim Berkland claims to have predicted the Loma Prieta quake,[95] but the mainstream scientific community does not endorse his techniques as repeatable, attributing his success with this quake partly to random chance.
In 1989 Iben Browning predicted a major earthquake in the New Madrid fault zone of southern Missouri and specified December 2 or 3, 1990, as the most likely days. This prediction was reported on extensively in the media and led to great community concern. No earthquake occurred on those days or thereafter.
In early 2004, a group of scientists at the University of California, Los Angeles, led by Dr. Vladimir Keilis-Borok, predicted that a quake similar in strength to the San Simeon earthquake of 2003 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 Prediction Evaluation Council (CEPEC) evaluated Keilis-Borok's prediction and reported to the California State Office of Emergency Services.[96] 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.
Italian technician Giampaolo Giuliani claims to have predicted the 2009 L'Aquila earthquake. He had previously been reported to Italian police for "causing fear" but he was acquitted.[97] Emission of radon as an earthquake precursor has been studied since the seventies, but the research has not resulted in successful prediction methods. The claim by Giuliani that he predicted the M6.3 L'Aquila earthquake of 6 April 2009 was investigated by the International Commission on Earthquake Forecasting established by the Italian government, but was not substantiated in their report.[98][99] Mr. Giuliani has never published any reports in peer reviewed scientific journals on his measurement methods, his analysis of the data, elimination of noise sources, and statistical correlation with earthquakes, something that would be required for taking prediction claims seriously. Mr. Giuliani presented his observations at the fall meeting of the American Geophysical Union (AGU)[4] in 2009,[100] where no work is reviewed or rejected . Contrary to some reports, Mr. Giuliani was not invited by anyone representing the American Geophysical Union to participate in any research project, according to P. Shearer, president of the Seismology Section of the AGU.