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152-414: Most aftershocks are located over the full area of fault rupture and either occur along the fault plane itself or along other faults within the volume affected by the strain associated with the main shock. Typically, aftershocks are found up to a distance equal to the rupture length away from the fault plane. The pattern of aftershocks helps confirm the size of area that slipped during the main shock. In both

304-663: A line source ). This greatly increased the geographical area over which the waves were observed, reaching as far as Mexico, Chile, and the Arctic. The raising of the seafloor significantly reduced the capacity of the Indian Ocean, producing a permanent rise in the global sea level by an estimated 0.1 mm (0.004 in). Numerous aftershocks were reported off the Andaman Islands , the Nicobar Islands and

456-466: A 2.6 m (8.5 ft) crest-to-trough tsunami was measured. As well, the tsunami was large enough to be detected in Vancouver , which puzzled many scientists, as the tsunamis measured in some parts of South America were larger than those measured in some parts of the Indian Ocean. It has been theorized that the tsunamis were focused and directed at long ranges by the mid-ocean ridges which run along

608-480: A busload of vacationers and locals to safety on higher ground. Anthropologists had initially expected the aboriginal population of the Andaman Islands to be badly affected by the tsunami and even feared the already depopulated Onge tribe could have been wiped out. Many of the aboriginal tribes evacuated and suffered fewer casualties, however. Oral traditions developed from previous earthquakes helped

760-618: A causal relationship between these events. The 2004 Indian Ocean earthquake is thought to have triggered activity in both Leuser Mountain and Mount Talang , volcanoes in Aceh along the same range of peaks, while the 2005 Nias–Simeulue earthquake sparked activity in Lake Toba , a massive caldera in Sumatra. The energy released on the Earth's surface ( M e , the energy magnitude, which

912-477: A dependence on space and a dependence on time. And more recently, through the application of a fractional solution of the reactive differential equation, a double power law model shows the number density decay in several possible ways, among which is a particular case the Utsu-Omori Law. The other main law describing aftershocks is known as Båth's Law and this states that the difference in magnitude between

1064-479: A few mosques remained standing. The greatest run-up height of the tsunami was measured at a hill between Lhoknga and Leupung , on the western coast of the northern tip of Sumatra, near Banda Aceh, and reached 51 m (167 ft). The tsunami heights in Sumatra: The island country of Sri Lanka, located about 1,700 km (1,100 mi) from Sumatra, was ravaged by the tsunami around two hours after

1216-569: A few to a few dozen seconds before the main shaking, and become alarmed or exhibit other unusual behavior. Seismometers can also detect P waves, and the timing difference is exploited by electronic earthquake warning systems to provide humans with a few seconds to move to a safer location. A review of scientific studies available as of 2018 covering over 130 species found insufficient evidence to show that animals could provide warning of earthquakes hours, days, or weeks in advance. Statistical correlations suggest some reported unusual animal behavior

1368-553: A given fault segment, identifying these characteristic earthquakes and timing their recurrence rate (or conversely return period ) should therefore inform us about the next rupture; this is the approach generally used in forecasting seismic hazard. UCERF3 is a notable example of such a forecast, prepared for the state of California. Return periods are also used for forecasting other rare events, such as cyclones and floods, and assume that future frequency will be similar to observed frequency to date. The idea of characteristic earthquakes

1520-442: A landmass between them and the tsunami's location of origin are usually safe; however, tsunami waves can sometimes diffract around such landmasses. Thus, the state of Kerala was hit by the tsunami despite being on the western coast of India, and the western coast of Sri Lanka suffered substantial impacts. Distance alone was no guarantee of safety, as Somalia was hit harder than Bangladesh despite being much farther away. Because of

1672-513: A large earthquake. Precursor methods are pursued largely because of their potential utility for short-term earthquake prediction or forecasting, while 'trend' methods are generally thought to be useful for forecasting, long term prediction (10 to 100 years time scale) or intermediate term prediction (1 to 10 years time scale). An earthquake precursor is an anomalous phenomenon that might give effective warning of an impending earthquake. Reports of these – though generally recognized as such only after

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1824-485: A large magnitude, and can collapse buildings that are damaged from the main shock. Bigger earthquakes have more and larger aftershocks and the sequences can last for years or even longer especially when a large event occurs in a seismically quiet area; see, for example, the New Madrid seismic zone , where events still follow Omori's law from the main shocks of 1811–1812. An aftershock sequence is deemed to have ended when

1976-453: A large turbulent bore. Eyewitnesses described the tsunami as a "black giant", "mountain" and a "wall of water". Video footage revealed torrents of black water, surging by windows of a two-story residential area situated about 3.2 km (2.0 mi) inland. Additionally, amateur footage recorded in the middle of the city captured an approaching black surge flowing down the city streets, full of debris, inundating them. The level of destruction

2128-477: A large-scale 'preparation zone' indicating the likely magnitude of a future event, remains as ethereal as the ether that went undetected in the Michelson–Morley experiment." V p is the symbol for the velocity of a seismic "P" (primary or pressure) wave passing through rock, while V s is the symbol for the velocity of the "S" (secondary or shear) wave. Small-scale laboratory experiments have shown that

2280-427: A less deformed state. In the process energy is released in various forms, including seismic waves. The cycle of tectonic force being accumulated in elastic deformation and released in a sudden rebound is then repeated. As the displacement from a single earthquake ranges from less than a meter to around 10 meters (for an M 8 quake), the demonstrated existence of large strike-slip displacements of hundreds of miles shows

2432-517: A low number of aftershocks and high foreshock rates compared to continental strike-slip faults . Seismologists use tools such as the Epidemic-Type Aftershock Sequence model (ETAS) to study cascading aftershocks and foreshocks. Following a large earthquake and aftershocks, many people have reported feeling "phantom earthquakes" when in fact no earthquake was taking place. This condition, known as "earthquake sickness"

2584-441: A low, broad hump, barely noticeable and harmless, which generally travels at the high speed of 500 to 1,000 km/h (310 to 620 mph); in shallow water near coastlines, a tsunami slows down to only tens of kilometres per hour but, in doing so, forms large destructive waves. Scientists investigating the damage in Aceh found evidence that the wave reached a height of 24 m (80 ft) when coming ashore along large stretches of

2736-401: A magnitude of as high as 6.9 ) and presently ranks as the third-largest earthquake ever recorded on the moment magnitude or Richter scale . Other aftershocks of up to magnitude 7.2 continued to shake the region daily for three or four months. As well as continuing aftershocks, the energy released by the original earthquake continued to make its presence felt well after the event. A week after

2888-644: A main shock and its largest aftershock is approximately constant, independent of the main shock magnitude, typically 1.1–1.2 on the Moment magnitude scale . Aftershock sequences also typically follow the Gutenberg–Richter law of size scaling, which refers to the relationship between the magnitude and total number of earthquakes in a region in a given time period. Where: In summary, there are more small aftershocks and fewer large aftershocks. Aftershocks are dangerous because they are usually unpredictable, can be of

3040-447: A major earthquake under ordinary circumstances but is dwarfed by the mainshock . The shift of mass and the massive release of energy slightly altered the Earth's rotation. Weeks after the earthquake, theoretical models suggested the earthquake shortened the length of a day by 2.68 microseconds , due to a decrease in the oblateness of the Earth. It also caused the Earth to minutely "wobble" on its axis by up to 25 mm (1 in) in

3192-610: A major earthquake, that does occur, or at least an adequate evaluation of the hazard, can result in legal liability, or even political purging. For example, it has been reported that members of the Chinese Academy of Sciences were purged for "having ignored scientific predictions of the disastrous Tangshan earthquake of summer 1976." Following the 2009 L'Aquila Earthquake , seven scientists and technicians in Italy were convicted of manslaughter, but not so much for failing to predict

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3344-486: A month after the earthquake found the movement to be about 0.2 m (8 in). Since movement was vertical as well as lateral, some coastal areas may have been moved to below sea level. The Andaman and Nicobar Islands appear to have shifted south-west by around 1.25 m (4 ft 1 in) and to have sunk by 1 m (3 ft 3 in). In February 2005, the Royal Navy vessel HMS  Scott surveyed

3496-402: A near-future earthquake. The flashbulb memory effect causes unremarkable details to become more memorable and more significant when associated with an emotionally powerful event such as an earthquake. Even the vast majority of scientific reports in the 2018 review did not include observations showing that animals did not act unusually when there was not an earthquake about to happen, meaning

3648-617: A network of sensors is needed to detect it. Tsunamis are more frequent in the Pacific Ocean than in other oceans because of earthquakes in the " Ring of Fire ". Although the extreme western edge of the Ring of Fire extends into the Indian Ocean (the point where the earthquake struck), no warning system exists in that ocean. Tsunamis there are relatively rare despite earthquakes being relatively frequent in Indonesia. The last major tsunami

3800-415: A newer approach to explain the phenomenon, NASA 's Friedmann Freund has proposed that the infrared radiation captured by the satellites is not due to a real increase in the surface temperature of the crust. According to this version the emission is a result of the quantum excitation that occurs at the chemical re-bonding of positive charge carriers ( holes ) which are traveling from the deepest layers to

3952-475: A number of reasons. First, it is believed that stress does not accumulate rapidly before a major earthquake, and thus there is no reason to expect large currents to be rapidly generated. Secondly, seismologists have extensively searched for statistically reliable electrical precursors, using sophisticated instrumentation, and have not identified any such precursors. And thirdly, water in the Earth's crust would cause any generated currents to be absorbed before reaching

4104-424: A practical method for predicting earthquakes would soon be found, but by the 1990s continuing failure led many to question whether it was even possible. Demonstrably successful predictions of large earthquakes have not occurred, and the few claims of success are controversial. For example, the most famous claim of a successful prediction is that alleged for the 1975 Haicheng earthquake . A later study said that there

4256-403: A rigorous statistical evaluation. Published results are biased towards positive results, and so the rate of false negatives (earthquake but no precursory signal) is unclear. After an earthquake has already begun, pressure waves ( P waves ) travel twice as fast as the more damaging shear waves ( s waves ). Typically not noticed by humans, some animals may notice the smaller vibrations that arrive

4408-423: A single block of rock some 100 m (330 ft) high and 2 km (1.2 mi) long. The momentum of the water displaced by tectonic uplift had also dragged massive slabs of rock, each weighing millions of tonnes, as far as 10 km (6 mi) across the seabed. An oceanic trench several kilometres wide was exposed in the earthquake zone. The TOPEX/Poseidon and Jason-1 satellites happened to pass over

4560-480: A single observation each. After a critical review of the scientific literature, the International Commission on Earthquake Forecasting for Civil Protection (ICEF) concluded in 2011 there was "considerable room for methodological improvements in this type of research." In particular, many cases of reported precursors are contradictory, lack a measure of amplitude, or are generally unsuitable for

4712-581: A successful albeit informal prediction in 1973, and it was credited for predicting the 1974 Riverside (CA) quake. However, additional successes have not followed, and it has been suggested that these predictions were a fluke. A V p / V s anomaly was the basis of a 1976 prediction of a M 5.5 to 6.5 earthquake near Los Angeles, which failed to occur. Other studies relying on quarry blasts (more precise, and repeatable) found no such variations, while an analysis of two earthquakes in California found that

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4864-489: Is additionally applied to the general subsequent seismicity of the area associated with the SES activity, in order to improve the time parameter of the prediction. The method treats earthquake onset as a critical phenomenon . A review of the updated VAN method in 2020 says that it suffers from an abundance of false positives and is therefore not usable as a prediction protocol. VAN group answered by pinpointing misunderstandings in

5016-434: Is believed to have been a foreshock , preceding the main event by over two years. Great earthquakes, such as the 2004 Indian Ocean earthquake, are associated with megathrust events in subduction zones. Their seismic moments can account for a significant fraction of the global seismic moment across century-scale periods. Of all the moment released by earthquakes in the 100 years from 1906 through 2005, roughly one eighth

5168-421: Is best representative of the earthquake's size. More recent studies estimate the magnitude to be M w  9.3. A 2016 study estimated the magnitude to be M w  9.25, while a 2021 study revised its 2007 estimate of M w  9.1 to a new magnitude of M w  9.2. The hypocentre of the main earthquake was approximately 160 km (100 mi) off the western coast of northern Sumatra, in

5320-540: Is derived entirely from the trend , which supposedly accounts for the unknown and possibly unknowable earthquake physics and fault parameters. However, in the Parkfield case the predicted earthquake did not occur until 2004, a decade late. This seriously undercuts the claim that earthquakes at Parkfield are quasi-periodic, and suggests the individual events differ sufficiently in other respects to question whether they have distinct characteristics in common. The failure of

5472-690: Is due to smaller earthquakes ( foreshocks ) that sometimes precede a large quake, which if small enough may go unnoticed by people. Foreshocks may also cause groundwater changes or release gases that can be detected by animals. Foreshocks are also detected by seismometers, and have long been studied as potential predictors, but without success (see #Seismicity patterns ). Seismologists have not found evidence of medium-term physical or chemical changes that predict earthquakes which animals might be sensing. Anecdotal reports of strange animal behavior before earthquakes have been recorded for thousands of years. Some unusual animal behavior may be mistakenly attributed to

5624-407: Is inherently impossible. Predictions are deemed significant if they can be shown to be successful beyond random chance. Therefore, methods of statistical hypothesis testing are used to determine the probability that an earthquake such as is predicted would happen anyway (the null hypothesis ). The predictions are then evaluated by testing whether they correlate with actual earthquakes better than

5776-405: Is more than twice the total explosive energy used during all of World War II (including the two atomic bombs) but still a couple of orders of magnitude less than the energy released in the earthquake itself. In many places, the waves reached as far as 2 km (1.2 mi) inland. Because the 1,600 km (1,000 mi) fault affected by the earthquake was in a nearly north–south orientation,

5928-427: Is observed that either the D layer is lost during the day resulting to ionosphere elevation and skywave formation or the D layer appears at night resulting to lower of the ionosphere and hence absence of skywave. Science centers have developed a network of VLF transmitters and receivers on a global scale that detect changes in skywave. Each receiver is also daisy transmitter for distances of 1000–10,000 kilometers and

6080-464: Is operating at different frequencies within the network. The general area under excitation can be determined depending on the density of the network. It was shown on the other hand that global extreme events like magnetic storms or solar flares and local extreme events in the same VLF path like another earthquake or a volcano eruption that occur in near time with the earthquake under evaluation make it difficult or impossible to relate changes in skywave to

6232-836: Is part of the Indo-Australian plate , which underlies the Indian Ocean and Bay of Bengal , and is moving north-east at an average of 60 mm/a (0.075 in/Ms). The India Plate meets the Burma plate (which is considered a portion of the great Eurasian plate ) at the Sunda Trench . At this point, the India Plate subducts beneath the Burma plate, which carries the Nicobar Islands, the Andaman Islands, and northern Sumatra. The India Plate sinks deeper and deeper beneath

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6384-482: Is the deadliest natural disaster of the 21st century , and the worst tsunami disaster in history. It is also the worst natural disaster in the history of Indonesia, Sri Lanka and Thailand. It was the most powerful earthquake ever recorded in Asia, the most powerful earthquake in the 21st century, and at least the third most powerful earthquake ever recorded in the world since modern seismography began in 1900. It had

6536-547: Is the seismic potential for damage ) by the 2004 Indian Ocean earthquake was estimated at 1.1 × 10 joules . The earthquake generated a seismic oscillation of the Earth's surface of up to 200–300 mm (8–12 in), equivalent to the effect of the tidal forces caused by the Sun and Moon. The seismic waves of the earthquake were felt across the planet, as far away as the U.S. state of Oklahoma , where vertical movements of 3 mm (0.12 in) were recorded. By February 2005,

6688-627: Is the estimate of the current dynamic state of a seismological system, based on natural time introduced in 2001. It differs from forecasting which aims to estimate the probability of a future event but it is also considered a potential base for forecasting. Nowcasting calculations produce the "earthquake potential score", an estimation of the current level of seismic progress. Typical applications are: great global earthquakes and tsunamis, aftershocks and induced seismicity, induced seismicity at gas fields, seismic risk to global megacities, studying of clustering of large global earthquakes, etc. Even

6840-417: Is thought to be related to motion sickness , and usually goes away as seismic activity tails off. 2004 Indian Ocean earthquake On 26 December 2004, at 07:58:53 local time ( UTC+7 ), a major earthquake with a magnitude of 9.2–9.3 M w struck with an epicentre off the west coast of northern Sumatra , Indonesia. The undersea megathrust earthquake , known by the scientific community as

6992-407: Is used in long-term forecasting, and was the basis of a series of circum-Pacific ( Pacific Rim ) forecasts in 1979 and 1989–1991. However, some underlying assumptions about seismic gaps are now known to be incorrect. A close examination suggests that "there may be no information in seismic gaps about the time of occurrence or the magnitude of the next large event in the region"; statistical tests of

7144-523: The 1812 New Madrid earthquake . Some scientists have tried to use foreshocks to help predict upcoming earthquakes , having one of their few successes with the 1975 Haicheng earthquake in China. On the East Pacific Rise however, transform faults show quite predictable foreshock behaviour before the main seismic event. Reviews of data of past events and their foreshocks showed that they have

7296-426: The 2004 Indian Ocean earthquake and the 2008 Sichuan earthquake , the aftershock distribution in each case showed that the epicenter (where the rupture initiated) lay to one end of the final area of slip, implying strongly asymmetric rupture propagation. Aftershocks rates and magnitudes follow several well-established empirical laws. The frequency of aftershocks decreases roughly with the reciprocal of time after

7448-673: The International Commission on Earthquake Forecasting for Civil Protection (ICEF) found the "most convincing" electromagnetic precursors to be ultra low frequency magnetic anomalies, such as the Corralitos event (discussed below) recorded before the 1989 Loma Prieta earthquake. However, it is now believed that observation was a system malfunction. Study of the closely monitored 2004 Parkfield earthquake found no evidence of precursory electromagnetic signals of any type; further study showed that earthquakes with magnitudes less than 5 do not produce significant transient signals. The ICEF considered

7600-541: The Parkfield prediction has raised doubt as to the validity of the characteristic earthquake model itself. Some studies have questioned the various assumptions, including the key one that earthquakes are constrained within segments, and suggested that the "characteristic earthquakes" may be an artifact of selection bias and the shortness of seismological records (relative to earthquake cycles). Other studies have considered whether other factors need to be considered, such as

7752-696: The Sumatra–Andaman earthquake , was caused by a rupture along the fault between the Burma plate and the Indian plate , and reached a Mercalli intensity of IX in some areas. A massive tsunami with waves up to 30 m (100 ft) high, known as the Boxing Day Tsunami after the Boxing Day holiday, or as the Asian Tsunami , devastated communities along the surrounding coasts of

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7904-506: The affected people and countries prompted a worldwide humanitarian response , with donations totalling more than US$ 14 billion (equivalent to US$ 23 billion in 2023 currency). The 2004 Indian Ocean earthquake was initially documented as having a moment magnitude of 8.8. The United States Geological Survey has its estimate of 9.1. Hiroo Kanamori of the California Institute of Technology estimates that M w  9.2

8056-569: The subduction zone where the Indian plate slides under (or subducts) the overriding Burma plate. The slip did not happen instantaneously but took place in two phases over several minutes: Seismographic and acoustic data indicate that the first phase involved a rupture about 400 km (250 mi) long and 100 km (60 mi) wide, 30 km (19 mi) beneath the sea bed—the largest rupture ever known to have been caused by an earthquake. The rupture proceeded at about 2.8 km/s (1.74 mi/s; 10,100 km/h; 6,260 mph), beginning off

8208-456: The ultra low frequency and extremely low frequency ranges that reach the surface of the Earth before an earthquake, causing odd behavior. These electromagnetic waves could also cause air ionization , water oxidation and possible water toxification which other animals could detect. In the 1970s the dilatancy–diffusion hypothesis was highly regarded as providing a physical basis for various phenomena seen as possible earthquake precursors. It

8360-471: The Burma plate until the increasing temperature and pressure drive volatiles out of the subducting plate. These volatiles rise into the overlying plate, causing partial melting and the formation of magma. The rising magma intrudes into the crust above and exits the Earth's crust through volcanoes in the form of a volcanic arc . The volcanic activity that results as the Indo-Australian plate subducts

8512-405: The Earth and Planetary Interiors in 2020 shows that solar weather and ionospheric disturbances are a potential cause to trigger large earthquakes based on this statistical relationship. The proposed mechanism is electromagnetic induction from the ionosphere to the fault zone. Fault fluids are conductive, and can produce telluric currents at depth. The resulting change in the local magnetic field in

8664-426: The Earth on the vertical axis (note the 1 cm scale bar at the bottom for scale). The seismograms are arranged vertically by distance from the epicentre in degrees. The earliest, lower amplitude signal is that of the compressional (P) wave , which takes about 22 minutes to reach the other side of the planet (the antipode ; in this case near Ecuador). The largest amplitude signals are seismic surface waves that reach

8816-424: The Earth. The skywave is lost during the day, as the D layer absorbs these waves. Tectonic stresses in the Earth's crust are claimed to cause waves of electric charges that travel to the surface of the Earth and affect the ionosphere. ULF * recordings of the daily cycle of the ionosphere indicate that the usual cycle could be disturbed a few days before a shallow strong earthquake. When the disturbance occurs, it

8968-518: The Eurasian plate has created the Sunda Arc . As well as the sideways movement between the plates, the 2004 Indian Ocean earthquake resulted in a rise of the seafloor by several metres, displacing an estimated 30 km (7.2 cu mi) of water and triggering devastating tsunami waves. The waves radiated outwards along the entire 1,600 km (1,000 mi) length of the rupture (acting as

9120-642: The Indian Ocean just north of Simeulue island at a depth of 30 km (19 mi) below mean sea level (initially reported as 10 km or 6.2 mi). The northern section of the Sunda megathrust ruptured over a length of 1,300 km (810 mi). The earthquake (followed by the tsunami) was felt in Bangladesh , India , Malaysia , Myanmar , Thailand , Sri Lanka and the Maldives . Splay faults, or secondary "pop up faults", caused long, narrow parts of

9272-404: The Indian Ocean, killing an estimated 227,898 people in 14 countries in one of the deadliest natural disasters in recorded history . The direct results caused major disruptions to living conditions and commerce in coastal provinces of surrounded countries, including Aceh (Indonesia), Sri Lanka , Tamil Nadu (India) and Khao Lak (Thailand). Banda Aceh reported the largest number of deaths. It

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9424-468: The Pacific Ocean. In comparison to the 2004 Indian Ocean earthquake, the death toll from these earthquakes and tsunamis was significantly lower, primarily because of the lower population density along the coasts near affected areas. Comparisons with earlier earthquakes are difficult, as earthquake strength was not measured systematically until the 1930s. However, historical earthquake strength can sometimes be estimated by examining historical descriptions of

9576-579: The VAN method, and therefore the predictive significance of SES, was based primarily on the empirical claim of demonstrated predictive success. Numerous weaknesses have been uncovered in the VAN methodology, and in 2011 the International Commission on Earthquake Forecasting for Civil Protection concluded that the prediction capability claimed by VAN could not be validated. Most seismologists consider VAN to have been "resoundingly debunked". On

9728-509: The aboriginal tribes escape the tsunami. For example, the folklore of the Onges talks of "huge shaking of ground followed by high wall of water". Almost all of the Onge people seemed to have survived the tsunami. The tsunami devastated the coastline of Aceh province, about 20 minutes after the earthquake. Banda Aceh , the closest major city, suffered severe casualties. The sea receded and exposed

9880-441: The age of the fault. Whether earthquake ruptures are more generally constrained within a segment (as is often seen), or break past segment boundaries (also seen), has a direct bearing on the degree of earthquake hazard: earthquakes are larger where multiple segments break, but in relieving more strain they will happen less often. At the contact where two tectonic plates slip past each other every section must eventually slip, as (in

10032-456: The antipode after about 100 minutes. The surface waves can be clearly seen to reinforce near the antipode (with the closest seismic stations in Ecuador), and to subsequently encircle the planet to return to the epicentral region after about 200 minutes. A major aftershock (magnitude 7.1) can be seen at the closest stations starting just after the 200-minute mark. The aftershock would be considered

10184-524: The behavior was not established to be predictive. Most researchers investigating animal prediction of earthquakes are in China and Japan. Most scientific observations have come from the 2010 Canterbury earthquake in New Zealand, the 1984 Nagano earthquake in Japan, and the 2009 L'Aquila earthquake in Italy. Animals known to be magnetoreceptive might be able to detect electromagnetic waves in

10336-401: The capital city. The tsunami reached a run-up of 10–20 m (33–66 ft) on the western shorelines of Breueh Island and Nasi Island . Coastal villages were destroyed by the waves. On Weh Island , strong surges were experienced in the port of Sabang , yet there was little damage with reported runup values of 3–5 m (9.8–16.4 ft), most likely due to the island being sheltered from

10488-588: The city was just at the level of the second floor, and there were large amounts of debris piled along the streets and in the ground-floor storefronts. In the seaside section of Ulee Lheue, the flow depths were over 9 m (30 ft). Footage showed evidence of back-flowing of the Aceh River , carrying debris and people from destroyed villages at the coast and transporting them up to 40 km (25 mi) inland. A group of small islands: Weh, Breueh, Nasi, Teunom , Bunta , Lumpat , and Batee lie just north of

10640-467: The coast and appeared like gigantic surfing waves but "taller than the coconut trees and was like a mountain". The second wave was the largest; it came from the west-southwest within five minutes of the first wave. The tsunami stranded cargo ships, barges and destroyed a cement mining facility near the Lampuuk coast, where it reached the fourth level of the building. Meulaboh , a remote coastal city,

10792-590: The coast of Aceh and proceeding north-westerly over about 100 seconds. After a pause of about another 100 seconds, the rupture continued northwards towards the Andaman and Nicobar Islands . The northern rupture occurred more slowly than in the south, at about 2.1 km/s (1.3 mi/s; 7,600 km/h; 4,700 mph), continuing north for another five minutes to a plate boundary where the fault type changes from subduction to strike-slip (the two plates slide past one another in opposite directions). The Indian plate

10944-516: The coastline, rising to 30 m (100 ft) in some areas when travelling inland. Radar satellites recorded the heights of tsunami waves in deep water: the maximum height was at 600 mm (2 ft) two hours after the earthquake, the first such observations ever made. According to Tad Murty , vice-president of the Tsunami Society, the total energy of the tsunami waves was equivalent to about 5 megatons of TNT (21  PJ ), which

11096-493: The credibility, and thereby the effectiveness, of future warnings. In 1999 it was reported that China was introducing "tough regulations intended to stamp out 'false' earthquake warnings, in order to prevent panic and mass evacuation of cities triggered by forecasts of major tremors." This was prompted by "more than 30 unofficial earthquake warnings ... in the past three years, none of which has been accurate." The acceptable trade-off between missed quakes and false alarms depends on

11248-508: The damage caused, and the geological records of the areas where they occurred. Some examples of significant historical megathrust earthquakes are the 1868 Arica earthquake in Peru and the 1700 Cascadia earthquake in western North America. The 2004 Indian Ocean earthquake was unusually large in geographical and geological extent. An estimated 1,600 km (1,000 mi) of fault surface slipped (or ruptured) about 15 m (50 ft) along

11400-638: The death toll on Greek highways is more than 2300 per year on average, he argued that more lives would also be saved if Greece's entire budget for earthquake prediction had been used for street and highway safety instead. Earthquake prediction is an immature science – it has not yet led to a successful prediction of an earthquake from first physical principles. Research into methods of prediction therefore focus on empirical analysis, with two general approaches: either identifying distinctive precursors to earthquakes, or identifying some kind of geophysical trend or pattern in seismicity that might precede

11552-446: The direct attack by the islands to the south-west. Lhoknga is a small coastal community about 13 km (8.1 mi) south-west of Banda Aceh, located on a flat coastal plain in between two rainforest -covered hills, overlooking a large bay and famous for its large swathe of white sandy beach and surfing activities. The locals reported 10 to 12 waves, with the second and third being the highest and most destructive. Interviews with

11704-461: The direction of 145° east longitude , or perhaps by up to 50 or 60 mm (2.0 or 2.4 in). Because of tidal effects of the Moon, the length of a day increases at an average of 15 microseconds per year, so any rotational change due to the earthquake will be lost quickly. Similarly, the natural Chandler wobble of the Earth, which in some cases can be up to 15 m (50 ft), eventually offset

11856-463: The distances involved, the tsunami took anywhere from fifteen minutes to seven hours to reach the coastlines. The northern regions of the Indonesian island of Sumatra were hit quickly, while Sri Lanka and the east coast of India were hit roughly 90 minutes to two hours later. Thailand was struck about two hours later despite being closer to the epicentre because the tsunami travelled more slowly in

12008-519: The earthquake of interest. In 2017, an article in the Journal of Geophysical Research showed that the relationship between ionospheric anomalies and large seismic events (M≥6.0) occurring globally from 2000 to 2014 was based on the presence of solar weather. When the solar data are removed from the time series, the correlation is no longer statistically significant. A subsequent article in Physics of

12160-412: The earthquake's effects were still detectable as a 20 μm (0.02 mm; 0.0008 in) complex harmonic oscillation of the Earth's surface, which gradually diminished and merged with the incessant free oscillation of the Earth more than four months after the earthquake. Because of its enormous energy release and shallow rupture depth, the earthquake generated remarkable seismic ground motions around

12312-496: The earthquake, its reverberations could still be measured, providing valuable scientific data about the Earth's interior. The 2004 Indian Ocean earthquake came just three days after a magnitude 8.1 earthquake in the sub-antarctic Auckland Islands , an uninhabited region west of New Zealand, and Macquarie Island to Australia's north. This is unusual since earthquakes of magnitude eight or more occur only about once per year on average. The U.S. Geological Survey sees no evidence of

12464-454: The earthquake, where some 300 people died, as for giving undue assurance to the populace – one victim called it "anaesthetizing" – that there would not be a serious earthquake, and therefore no need to take precautions. But warning of an earthquake that does not occur also incurs a cost: not only the cost of the emergency measures themselves, but of civil and economic disruption. False alarms, including alarms that are canceled, also undermine

12616-525: The earthquake. Additional magnetometers were subsequently deployed across northern and southern California, but after ten years and several large earthquakes, similar signals have not been observed. More recent studies have cast doubt on the connection, attributing the Corralitos signals to either unrelated magnetic disturbance or, even more simply, to sensor-system malfunction. In his investigations of crystalline physics, Friedemann Freund found that water molecules embedded in rock can dissociate into ions if

12768-499: The earthquake. The tsunami first struck the eastern coastline and subsequently refracted around the southern point of Sri Lanka ( Dondra Head ). The refracted tsunami waves then inundated the southwestern part of Sri Lanka after some of its energy was reflected from impact with the Maldives. In Sri Lanka, the civilian casualties were second only to those in Indonesia, with approximately 35,000 killed. The eastern shores of Sri Lanka were

12920-537: The earthquakes with which these changes are supposedly linked were up to a thousand kilometers away, months later, and at all magnitudes. In some cases the anomalies were observed at a distant site, but not at closer sites. The ICEF found "no significant correlation". Observations of electromagnetic disturbances and their attribution to the earthquake failure process go back as far as the Great Lisbon earthquake of 1755, but practically all such observations prior to

13072-429: The entire fault should have similar characteristics. These include the maximum magnitude (which is limited by the length of the rupture), and the amount of accumulated strain needed to rupture the fault segment. Since continuous plate motions cause the strain to accumulate steadily, seismic activity on a given segment should be dominated by earthquakes of similar characteristics that recur at somewhat regular intervals. For

13224-440: The epicenter of the impending earthquake, started showing anomalous increases in amplitude. Just three hours before the quake, the measurements soared to about thirty times greater than normal, with amplitudes tapering off after the quake. Such amplitudes had not been seen in two years of operation, nor in a similar instrument located 54 km away. To many people such apparent locality in time and space suggested an association with

13376-594: The event – number in the thousands, some dating back to antiquity. There have been around 400 reports of possible precursors in scientific literature, of roughly twenty different types, running the gamut from aeronomy to zoology. None have been found to be reliable for the purposes of earthquake prediction. In the early 1990, the IASPEI solicited nominations for a Preliminary List of Significant Precursors. Forty nominations were made, of which five were selected as possible significant precursors, with two of those based on

13528-592: The existence of a long running earthquake cycle. The most studied earthquake faults (such as the Nankai megathrust , the Wasatch Fault , and the San Andreas Fault ) appear to have distinct segments. The characteristic earthquake model postulates that earthquakes are generally constrained within these segments. As the lengths and other properties of the segments are fixed, earthquakes that rupture

13680-518: The fault triggers dissolution of minerals and weakens the rock, while also potentially changing the groundwater chemistry and level. After the seismic event, different minerals may be precipitated thus changing groundwater chemistry and level again. This process of mineral dissolution and precipitation before and after an earthquake has been observed in Iceland. This model makes sense of the ionospheric, seismic and groundwater data. One way of detecting

13832-501: The first level of a hotel, causing destruction and taking people unaware. Other videos recorded showed that the tsunami appeared like a flood raging inland. The construction of seawalls and breakwaters reduced the power of waves at some locations. The largest run-up measured was at 12.5 m (41 ft) with inundation distance of 390–1,500 m (1,280–4,920 ft) in Yala . In Hambantota , run-ups measured 11 m (36 ft) with

13984-517: The globe, particularly due to huge Rayleigh (surface) elastic waves that exceeded 10 mm (0.4 in) in vertical amplitude everywhere on Earth. The record section plot displays vertical displacements of the Earth's surface recorded by seismometers from the IRIS/USGS Global Seismographic Network plotted with respect to time (since the earthquake initiation) on the horizontal axis, and vertical displacements of

14136-488: The greatest inundation distance of 2 km (1.2 mi). Run-up measurements along the Sri Lankan coasts are at 2.4–4.11 m (7 ft 10 in – 13 ft 6 in). Waves measured on the east coast ranged from 4.5–9 m (15–30 ft) at Pottuvill to Batticaloa at 2.6–5 m (8 ft 6 in – 16 ft 5 in) in the north-east around Trincomalee and 4–5 m (13–16 ft) in

14288-468: The greatest strength of the tsunami waves was in an east–west direction. Bangladesh , which lies at the northern end of the Bay of Bengal , had few casualties despite being a low-lying country relatively near the epicentre. It also benefited from the fact that the earthquake proceeded more slowly in the northern rupture zone, greatly reducing the energy of the water displacements in that region. Coasts that have

14440-461: The hardest hit since it faced the epicentre of the earthquake, while the southwestern shores were hit later, but the death toll was just as severe. The southwestern shores are a hotspot for tourists and fishing. The degradation of the natural environment in Sri Lanka contributed to the high death tolls. Approximately 90,000 buildings and many wooden houses were destroyed. The tsunami arrived on

14592-442: The island as a small brown-orange-coloured flood. Moments later, the ocean floor was exposed as much as 1 km (0.62 mi) in places, which was followed by massive second and third waves. Amateur video recorded at the city of Galle showed a large deluge flooding the city, carrying debris and sweeping away people while in the coastal resort town of Beruwala , the tsunami appeared as a huge brown-orange-coloured bore which reached

14744-505: The lead-time of VAN prediction to only a few days [Uyeda and Kamogawa 2008]. This means, seismic data may play an amazing role in short term precursor when combined with SES data". Since 2001, the VAN group has introduced a concept they call "natural time", applied to the analysis of their precursors. Initially it is applied on SES to distinguish them from noise and relate them to a possible impending earthquake. In case of verification (classification as "SES activity"), natural time analysis

14896-416: The locals revealed that the sea temporarily receded and exposed coral reefs . In the distant horizon, gigantic black waves about 30 m (98 ft) high made explosion-like sounds as they broke and approached the shore. The first wave came rapidly landward from the south-west as a turbulent bore about 0.5–2.5 m (1.6–8.2 ft) high. The second and third waves were 15–30 m (49–98 ft) high at

15048-443: The long-term) none get left behind. But they do not all slip at the same time; different sections will be at different stages in the cycle of strain (deformation) accumulation and sudden rebound. In the seismic gap model the "next big quake" should be expected not in the segments where recent seismicity has relieved the strain, but in the intervening gaps where the unrelieved strain is the greatest. This model has an intuitive appeal; it

15200-404: The longest fault rupture ever observed, between 1,200 km and 1,300 km (720 mi and 780 mi), and had the longest duration of faulting ever observed, at least ten minutes. It caused the planet to vibrate as much as 10 mm (0.4 in), and also remotely triggered earthquakes as far away as Alaska . Its epicentre was between Simeulue and mainland Sumatra. The plight of

15352-436: The main shock. This empirical relation was first described by Fusakichi Omori in 1894 and is known as Omori's law. It is expressed as where k and c are constants, which vary between earthquake sequences. A modified version of Omori's law, now commonly used, was proposed by Utsu in 1961. where p is a third constant which modifies the decay rate and typically falls in the range 0.7–1.5. According to these equations,

15504-421: The margins of the continental plates. Despite a delay of up to several hours between the earthquake and the impact of the tsunami, nearly all of the victims were taken by surprise. There were no tsunami warning systems in the Indian Ocean to detect tsunamis or to warn the general population living around the ocean. Tsunami detection is difficult because while a tsunami is in deep water, it has little height and

15656-589: The mid-1960s are invalid because the instruments used were sensitive to physical movement. Since then various anomalous electrical, electric-resistive, and magnetic phenomena have been attributed to precursory stress and strain changes that precede earthquakes, raising hopes for finding a reliable earthquake precursor. While a handful of researchers have gained much attention with either theories of how such phenomena might be generated, claims of having observed such phenomena prior to an earthquake, no such phenomena has been shown to be an actual precursor. A 2011 review by

15808-423: The minor wobble produced by the earthquake. There was 10 m (33 ft) movement laterally and 4–5 m (13–16 ft) vertically along the fault line. Early speculation was that some of the smaller islands south-west of Sumatra, which is on the Burma plate (the southern regions are on the Sunda plate ), might have moved south-west by up to 36 m (120 ft), but more accurate data released more than

15960-674: The minutes preceding a tsunami strike, the sea sometimes recedes temporarily from the coast, which was observed on the eastern earthquake rupture zone such as the coastlines of Aceh, Phuket island, and Khao Lak area in Thailand, Penang island of Malaysia, and the Andaman and Nicobar islands . This rare sight reportedly induced people, especially children, to visit the coast to investigate and collect stranded fish on as much as 2.5 km (1.6 mi) of exposed beach, with fatal results. However, not all tsunamis cause this "disappearing sea" effect. In some cases, there are no warning signs at all:

16112-416: The mobility of tectonic stresses is to detect locally elevated temperatures on the surface of the crust measured by satellites . During the evaluation process, the background of daily variation and noise due to atmospheric disturbances and human activities are removed before visualizing the concentration of trends in the wider area of a fault. This method has been experimentally applied since 1995. In

16264-564: The null hypothesis. In many instances, however, the statistical nature of earthquake occurrence is not simply homogeneous. Clustering occurs in both space and time. In southern California about 6% of M≥3.0 earthquakes are "followed by an earthquake of larger magnitude within 5 days and 10 km." In central Italy 9.5% of M≥3.0 earthquakes are followed by a larger event within 48 hours and 30 km. While such statistics are not satisfactory for purposes of prediction (giving ten to twenty false alarms for each successful prediction) they will skew

16416-517: The other hand, the Section "Earthquake Precursors and Prediction" of "Encyclopedia of Solid Earth Geophysics: part of "Encyclopedia of Earth Sciences Series" (Springer 2011) ends as follows (just before its summary): "it has recently been shown that by analyzing time-series in a newly introduced time domain "natural time", the approach to the critical state can be clearly identified [Sarlis et al. 2008]. This way, they appear to have succeeded in shortening

16568-464: The parameters of the source earthquake without having to compensate for the complex ways in which proximity to the coast changes the size and shape of a wave. Before the 2004 quake there were three arguments against a large earthquake occurring in the Sumatra region. After the quake it was considered that earthquake hazard risk would need to be reassessed for regions previously thought to have low risk based on these criteria: The sudden vertical rise of

16720-414: The probabilistic assessment of general earthquake hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. Prediction can be further distinguished from earthquake warning systems , which, upon detection of an earthquake, provide a real-time warning of seconds to neighboring regions that might be affected. In the 1970s, scientists were optimistic that

16872-491: The probability of the first day (when p is equal to 1). These patterns describe only the statistical behavior of aftershocks; the actual times, numbers and locations of the aftershocks are stochastic , while tending to follow these patterns. As this is an empirical law, values of the parameters are obtained by fitting to data after a mainshock has occurred, and they imply no specific physical mechanism in any given case. The Utsu-Omori law has also been obtained theoretically, as

17024-408: The rate of aftershocks decreases quickly with time. The rate of aftershocks is proportional to the inverse of time since the mainshock and this relationship can be used to estimate the probability of future aftershock occurrence. Thus whatever the probability of an aftershock are on the first day, the second day will have 1/2 the probability of the first day and the tenth day will have approximately 1/10

17176-620: The rate of seismicity drops back to a background level; i.e., no further decay in the number of events with time can be detected. Land movement around the New Madrid is reported to be no more than 0.2 mm (0.0079 in) a year, in contrast to the San Andreas Fault which averages up to 37 mm (1.5 in) a year across California. Aftershocks on the San Andreas are now believed to top out at 10 years while earthquakes in New Madrid were considered aftershocks nearly 200 years after

17328-652: The ratio of these two velocities – represented as V p / V s – changes when rock is near the point of fracturing. In the 1970s it was considered a likely breakthrough when Russian seismologists reported observing such changes (later discounted. ) in the region of a subsequent earthquake. This effect, as well as other possible precursors, has been attributed to dilatancy, where rock stressed to near its breaking point expands (dilates) slightly. Study of this phenomenon near Blue Mountain Lake in New York State led to

17480-463: The region of the original epicentre in the hours and days that followed. The magnitude 8.6 2005 Nias–Simeulue earthquake , which originated off the coast of the Sumatran island of Nias , is not considered an aftershock, despite its proximity to the epicentre, and was most likely triggered by stress changes associated with the 2004 event. The earthquake produced its own aftershocks (some registering

17632-413: The region's north and east coast were Pidie Regency , Samalanga , Panteraja , and Lhokseumawe . The high fatality rate in the area was mainly due to lack of preparation of the community towards a tsunami and limited knowledge and education among the population regarding the natural phenomenon. Helicopter surveys revealed entire settlements virtually destroyed, with destruction extending miles inland. Only

17784-524: The relative velocities of the primary and secondary seismic waves – expressed as Vp/Vs – as they passed through a certain zone was the basis for predicting the 1973 Blue Mountain Lake (NY) and 1974 Riverside (CA) quake. Although these predictions were informal and even trivial, their apparent success was seen as confirmation of both dilatancy and the existence of a preparatory process, leading to what were subsequently called "wildly over-optimistic statements" that successful earthquake prediction "appears to be on

17936-412: The results of any analysis that assumes that earthquakes occur randomly in time, for example, as realized from a Poisson process . It has been shown that a "naive" method based solely on clustering can successfully predict about 5% of earthquakes; "far better than 'chance'". As the purpose of short-term prediction is to enable emergency measures to reduce death and destruction, failure to give warning of

18088-520: The rock is under intense stress. The resulting charge carriers can generate battery currents under certain conditions. Freund suggested that perhaps these currents could be responsible for earthquake precursors such as electromagnetic radiation, earthquake lights and disturbances of the plasma in the ionosphere. The study of such currents and interactions is known as "Freund physics". Most seismologists reject Freund's suggestion that stress-generated signals can be detected and put to use as precursors, for

18240-564: The rock. One of these gases is radon , produced by radioactive decay of the trace amounts of uranium present in most rock. Radon is potentially useful as an earthquake predictor because it is radioactive and thus easily detected, and its short half-life (3.8 days) makes radon levels sensitive to short-term fluctuations. A 2009 compilation listed 125 reports of changes in radon emissions prior to 86 earthquakes since 1966. The International Commission on Earthquake Forecasting for Civil Protection (ICEF) however found in its 2011 critical review that

18392-470: The sea will suddenly swell without retreating, surprising many people and giving them little time to flee. One of the few coastal areas to evacuate ahead of the tsunami was on the Indonesian island of Simeulue , close to the epicentre. Island folklore recounted an earthquake and tsunami in 1907 , and the islanders fled to inland hills after the initial shaking and before the tsunami struck. These tales and oral folklore from previous generations may have helped

18544-502: The seabed around the earthquake zone, which varies in depth between 1,000 and 5,000 m (550 and 2,730 fathoms; 3,300 and 16,400 ft). The survey, conducted using a high-resolution, multi-beam sonar system, revealed that the earthquake had made a considerable impact on the topography of the seabed. 1,500-metre-high (5,000 ft) thrust ridges created by previous geologic activity along the fault had collapsed, generating landslides several kilometres wide. One such landslide consisted of

18696-485: The seabed by several metres during the earthquake displaced massive volumes of water, resulting in a tsunami that struck the coasts of the Indian Ocean. A tsunami that causes damage far away from its source is sometimes called a teletsunami and is much more likely to be produced by the vertical motion of the seabed than by horizontal motion. The tsunami, like all the others, behaved differently in deep water than in shallow water. In deep ocean water, tsunami waves form only

18848-411: The seabed, prompting locals to collect stranded fish and explore the area. Local eyewitnesses described three large waves, with the first wave rising gently to the foundation of the buildings, followed minutes later by a sudden withdrawal of the sea near the port of Ulèë Lheue . This was succeeded by the appearance of two large black-coloured steep waves which then travelled inland into the capital city as

19000-514: The seafloor to pop up in seconds. This quickly elevated the height and increased the speed of waves, destroying the nearby Indonesian town of Lhoknga . Indonesia lies between the Pacific Ring of Fire along the north-eastern islands adjacent to New Guinea , and the Alpide belt that runs along the south and west from Sumatra, Java , Bali , Flores to Timor . The 2002 Sumatra earthquake

19152-575: The search for useful precursors to have been unsuccessful. The most touted, and most criticized, claim of an electromagnetic precursor is the VAN method of physics professors Panayiotis Varotsos , Kessar Alexopoulos and Konstantine Nomicos (VAN) of the University of Athens . In a 1981 paper they claimed that by measuring geoelectric voltages – what they called "seismic electric signals" (SES) – they could predict earthquakes. In 1984, they claimed there

19304-475: The shallow Andaman Sea off its western coast. The tsunami was noticed as far as Struisbaai in South Africa, about 8,500 km (5,300 mi) away, where a 1.5-metre-high (5 ft) tide surged on shore about 16 hours after the earthquake. It took a relatively long time to reach Struisbaai at the southernmost point of Africa, probably because of the broad continental shelf off South Africa and because

19456-422: The shoreline, houses, except for strongly-built reinforced concrete ones with brick walls, which seemed to have been partially damaged by the earthquake before the tsunami attack, were swept away or destroyed by the tsunami. The area toward the sea was wiped clean of nearly every structure, while closer to the river, dense construction in a commercial district showed the effects of severe flooding. The flow depth at

19608-883: The societal valuation of these outcomes. The rate of occurrence of both must be considered when evaluating any prediction method. In a 1997 study of the cost-benefit ratio of earthquake prediction research in Greece, Stathis Stiros suggested that even a (hypothetical) excellent prediction method would be of questionable social utility, because "organized evacuation of urban centers is unlikely to be successfully accomplished", while "panic and other undesirable side-effects can also be anticipated." He found that earthquakes kill less than ten people per year in Greece (on average), and that most of those fatalities occurred in large buildings with identifiable structural issues. Therefore, Stiros stated that it would be much more cost-effective to focus efforts on identifying and upgrading unsafe buildings. Since

19760-408: The solution of a differential equation describing the evolution of the aftershock activity, where the interpretation of the evolution equation is based on the idea of deactivation of the faults in the vicinity of the main shock of the earthquake. Also, previously Utsu-Omori law was obtained from a nucleation process. Results show that the spatial and temporal distribution of aftershocks is separable into

19912-510: The specific reasoning. Probably the most celebrated seismo-electromagnetic event ever, and one of the most frequently cited examples of a possible earthquake precursor, is the 1989 Corralitos anomaly. In the month prior to the 1989 Loma Prieta earthquake , measurements of the Earth's magnetic field at ultra-low frequencies by a magnetometer in Corralitos, California , just 7 km from

20064-426: The stiffest of rock is not perfectly rigid. Given a large force (such as between two immense tectonic plates moving past each other) the Earth's crust will bend or deform. According to the elastic rebound theory of Reid (1910) , eventually the deformation (strain) becomes great enough that something breaks, usually at an existing fault. Slippage along the break (an earthquake) allows the rock on each side to rebound to

20216-882: The surface of the crust at a speed of 200 meters per second. The electric charge arises as a result of increasing tectonic stresses as the time of the earthquake approaches. This emission extends superficially up to 500 x 500 square kilometers for very large events and stops almost immediately after the earthquake. Instead of watching for anomalous phenomena that might be precursory signs of an impending earthquake, other approaches to predicting earthquakes look for trends or patterns that lead to an earthquake. As these trends may be complex and involve many variables, advanced statistical techniques are often needed to understand them, therefore these are sometimes called statistical methods. These approaches also tend to be more probabilistic, and to have larger time periods, and so merge into earthquake forecasting. Earthquake nowcasting , suggested in 2016

20368-417: The surface. The ionosphere usually develops its lower D layer during the day, while at night this layer disappears as the plasma there turns to gas . During the night, the F layer of the ionosphere remains formed, in higher altitude than D layer. A waveguide for low HF radio frequencies up to 10 MHz is formed during the night ( skywave propagation) as the F layer reflects these waves back to

20520-446: The survival of the inhabitants. On Maikhao Beach in north Phuket City , Thailand, a 10-year-old British tourist named Tilly Smith had studied tsunamis in geography at school and recognised the warning signs of the receding ocean and frothing bubbles. She and her parents warned others on the beach, which was evacuated safely. John Chroston , a biology teacher from Scotland, also recognised the signs at Kamala Bay north of Phuket, taking

20672-457: The top of the train. Earthquake prediction Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the next strong earthquake to occur in a region". Earthquake prediction is sometimes distinguished from earthquake forecasting , which can be defined as

20824-431: The tsunami as it was crossing the ocean. These satellites carry radars that measure precisely the height of the water surface; anomalies in the order of 500 mm (20 in) were measured. Measurements from these satellites may prove invaluable for the understanding of the earthquake and tsunami. Unlike data from tide gauges installed on shores, measurements obtained in the middle of the ocean can be used for computing

20976-573: The tsunami would have followed the South African coast from east to west. The tsunami also reached Antarctica, where tidal gauges at Japan's Showa Base recorded oscillations of up to a metre (3 ft 3 in), with disturbances lasting a couple of days. Some of the tsunami's energy escaped into the Pacific Ocean, where it produced small but measurable tsunamis along the western coasts of North and South America, typically around 200 to 400 mm (7.9 to 15.7 in). At Manzanillo , Mexico,

21128-496: The variations reported were more likely caused by other factors, including retrospective selection of data. Geller (1997) noted that reports of significant velocity changes have ceased since about 1980. Most rock contains small amounts of gases that can be isotopically distinguished from the normal atmospheric gases. There are reports of spikes in the concentrations of such gases prior to a major earthquake; this has been attributed to release due to pre-seismic stress or fracturing of

21280-523: The verge of practical reality." However, many studies questioned these results, and the hypothesis eventually languished. Subsequent study showed it "failed for several reasons, largely associated with the validity of the assumptions on which it was based", including the assumption that laboratory results can be scaled up to the real world. Another factor was the bias of retrospective selection of criteria. Other studies have shown dilatancy to be so negligible that Main et al. 2012 concluded: "The concept of

21432-526: The very strong likelihood that the signals were man-made. Further work in Greece has tracked SES-like "anomalous transient electric signals" back to specific human sources, and found that such signals are not excluded by the criteria used by VAN to identify SES. More recent work, by employing modern methods of statistical physics, i.e., detrended fluctuation analysis (DFA), multifractal DFA and wavelet transform revealed that SES are clearly distinguished from signals produced by man made sources. The validity of

21584-518: The west coast from Moratuwa to Ambalangoda . Sri Lanka tsunami height survey: A regular passenger train operating between Maradana and Matara was derailed and overturned by the tsunami and claimed at least 1,700 lives, the largest single rail disaster death toll in history. Estimates based on the state of the shoreline and a high-water mark on a nearby building place the tsunami 7.5–9 m (25–30 ft) above sea level and 2–3 m (6 ft 7 in – 9 ft 10 in) higher than

21736-420: Was "saluted by some as a major breakthrough", among seismologists it was greeted by a "wave of generalized skepticism". In 1996, a paper VAN submitted to the journal Geophysical Research Letters was given an unprecedented public peer-review by a broad group of reviewers, with the paper and reviews published in a special issue; the majority of reviewers found the methods of VAN to be flawed. Additional criticism

21888-411: Was a "one-to-one correspondence" between SES and earthquakes – that is, that " every sizable EQ is preceded by an SES and inversely every SES is always followed by an EQ the magnitude and the epicenter of which can be reliably predicted" – the SES appearing between 6 and 115 hours before the earthquake. As proof of their method they claimed a series of successful predictions. Although their report

22040-471: Was among the hardest hit by the tsunami. The waves arrived after the sea receded about 500 m (1,600 ft), followed by an advancing small tsunami. The second and third destructive waves arrived later, which exceeded the height of the coconut trees. The inundation distance is about 5 km (3.1 mi). Other towns on Aceh's west coast hit by the disaster included Leupung , Lhokruet , Lamno , Patek, Calang , and Teunom . Affected or destroyed towns on

22192-491: Was based on "solid and repeatable evidence" from laboratory experiments that highly stressed crystalline rock experienced a change in volume, or dilatancy , which causes changes in other characteristics, such as seismic velocity and electrical resistivity, and even large-scale uplifts of topography. It was believed this happened in a 'preparatory phase' just prior to the earthquake, and that suitable monitoring could therefore warn of an impending quake. Detection of variations in

22344-418: Was caused by the 1883 eruption of Krakatoa . Not every earthquake produces large tsunamis: on 28 March 2005, a magnitude 8.7 earthquake hit roughly the same area of the Indian Ocean but did not result in a major tsunami. The first warning sign of a possible tsunami is the earthquake itself. However, tsunamis can strike thousands of kilometres away where the earthquake is felt only weakly or not at all. Also, in

22496-885: Was due to the 2004 Indian Ocean earthquake. This quake, together with the Great Alaskan earthquake (1964) and the Great Chilean earthquake (1960), account for almost half of the total moment. Since 1900, the only earthquakes recorded with a greater magnitude were the 1960 Valdivia earthquake (magnitude 9.5) and the 1964 Alaska earthquake in Prince William Sound (magnitude 9.2). The only other recorded earthquakes of magnitude 9.0 or greater were off Kamchatka , Russia, on 5 November 1952 (magnitude 9.0) and Tōhoku, Japan (magnitude 9.1) in March 2011 . Each of these megathrust earthquakes also spawned tsunamis in

22648-420: Was extreme on the northwestern areas of the city, immediately inland of the aquaculture ponds, and directly facing the Indian Ocean. The tsunami height was reduced from 12 m (39 ft) at Ulee Lheue to 6 m (20 ft) a further 8 km (5.0 mi) to the north-east. The inundation was observed to extend 3–4 km (1.9–2.5 mi) inland throughout the city. Within 2–3 km (1.2–1.9 mi) of

22800-472: Was no valid short-term prediction. Extensive searches have reported many possible earthquake precursors, but, so far, such precursors have not been reliably identified across significant spatial and temporal scales. While part of the scientific community hold that, taking into account non-seismic precursors and given enough resources to study them extensively, prediction might be possible, most scientists are pessimistic and some maintain that earthquake prediction

22952-418: Was raised the same year in a public debate between some of the principals. A primary criticism was that the method is geophysically implausible and scientifically unsound. Additional objections included the demonstrable falsity of the claimed one-to-one relationship of earthquakes and SES, the unlikelihood of a precursory process generating signals stronger than any observed from the actual earthquakes, and

23104-403: Was the basis of the Parkfield prediction : fairly similar earthquakes in 1857, 1881, 1901, 1922, 1934, and 1966 suggested a pattern of breaks every 21.9 years, with a standard deviation of ±3.1 years. Extrapolation from the 1966 event led to a prediction of an earthquake around 1988, or before 1993 at the latest (at the 95% confidence interval). The appeal of such a method is that the prediction

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