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79-506: Download coordinates as: Operation Plumbbob was a series of nuclear tests that were conducted between May 28 and October 7, 1957, at the Nevada Test Site , following Project 57 , and preceding Project 58/58A . The operation consisted of 29 explosions , of which only two did not produce any nuclear yield . Twenty-one laboratories and government agencies were involved. While most Operation Plumbbob tests contributed to

158-540: A plane crash . The John shot on July 19, 1957, was the only test of the Air Force's AIR-2A Genie rocket with a nuclear warhead. It was fired from an F-89J Scorpion fighter over Yucca Flats at the Nevada National Security Site . On the ground, the Air Force carried out a public relations event by having five Air Force officers and a motion picture photographer stand under ground zero of

237-450: A 900-kilogram (2,000 lb) iron lid was welded over the borehole to contain the nuclear blast, despite Brownlee predicting that it would not work. When Pascal-B was detonated, the blast went straight up the test shaft, launching the cap into the atmosphere. The plate was never found. Scientists believe compression heating caused the cap to vaporize as it sped through the atmosphere. A high-speed camera, which took one frame per millisecond ,

316-507: A given weapon type for a country is included, as well as tests that were otherwise notable (such as the largest test ever). All yields (explosive power) are given in their estimated energy equivalents in kilotons of TNT (see TNT equivalent ). Putative tests (like Vela incident ) have not been included. Seismology Seismology ( / s aɪ z ˈ m ɒ l ə dʒ i , s aɪ s -/ ; from Ancient Greek σεισμός ( seismós ) meaning " earthquake " and -λογία ( -logía ) meaning "study of")

395-505: A mantle of silicates, surrounding a core of iron. In 1906 Richard Dixon Oldham identified the separate arrival of P waves , S-waves and surface waves on seismograms and found the first clear evidence that the Earth has a central core. In 1909, Andrija Mohorovičić , one of the founders of modern seismology, discovered and defined the Mohorovičić discontinuity . Usually referred to as

474-399: A month after the event. The first observations of normal modes were made in the 1960s as the advent of higher fidelity instruments coincided with two of the largest earthquakes of the 20th century the 1960 Valdivia earthquake and the 1964 Alaska earthquake . Since then, the normal modes of the Earth have given us some of the strongest constraints on the deep structure of the Earth. One of

553-412: A near-surface explosion, and are much weaker for deep earthquake sources. Both body and surface waves are traveling waves; however, large earthquakes can also make the entire Earth "ring" like a resonant bell. This ringing is a mixture of normal modes with discrete frequencies and periods of approximately an hour or shorter. Normal mode motion caused by a very large earthquake can be observed for up to

632-506: A number of populated islands in nearby atoll formations. Though they were soon evacuated, many of the islands' inhabitants suffered from radiation burns and later from other effects such as increased cancer rate and birth defects, as did the crew of the Japanese fishing boat Daigo Fukuryū Maru . One crewman died from radiation sickness after returning to port, and it was feared that the radioactive fish they had been carrying had made it into

711-453: A particular location within a particular time-span, and they are routinely used in earthquake engineering . Public controversy over earthquake prediction erupted after Italian authorities indicted six seismologists and one government official for manslaughter in connection with a magnitude 6.3 earthquake in L'Aquila, Italy on April 5, 2009 . A report in Nature stated that the indictment

790-532: A result of a scenario of a concentrated number of nuclear explosions in a nuclear holocaust , the thousands of tests, hundreds being atmospheric, did nevertheless produce a global fallout that has peaked in 1963 (the Bomb pulse ), reaching levels of about 0.15  mSv per year worldwide, or about 7% of average background radiation dose from all sources, and has slowly decreased since, with natural environmental radiation levels being around 1 mSv . This global fallout

869-473: A single salvo test; Pakistan's second and last official test exploded four different devices. Almost all lists in the literature are lists of tests; in the lists in Misplaced Pages (for example, Operation Cresset has separate items for Cremino and Caerphilly , which together constitute a single test), the lists are of explosions. Separately from these designations, nuclear tests are also often categorized by

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948-518: A special meeting in L'Aquila the week before the earthquake occurred, scientists and officials were more interested in pacifying the population than providing adequate information about earthquake risk and preparedness. In locations where a historical record exists it may be used to estimate the timing, location and magnitude of future seismic events. There are several interpretative factors to consider. The epicentres or foci and magnitudes of historical earthquakes are subject to interpretation meaning it

1027-447: A variety of fissile material compositions, densities, shapes, and reflectors . They can be subcritical or supercritical, in which case significant radiation fluxes can be produced. This type of test has resulted in several criticality accidents . Subcritical (or cold) tests are any type of tests involving nuclear materials and possibly high explosives (like those mentioned above) that purposely result in no yield . The name refers to

1106-569: A very short time frame in a seismic cycle . Engineering seismology is the study and application of seismology for engineering purposes. It generally applied to the branch of seismology that deals with the assessment of the seismic hazard of a site or region for the purposes of earthquake engineering. It is, therefore, a link between earth science and civil engineering . There are two principal components of engineering seismology. Firstly, studying earthquake history (e.g. historical and instrumental catalogs of seismicity) and tectonics to assess

1185-568: A weapon, and projects concerning earth motion, blast loading and neutron output were carried out. Nuclear weapons safety experiments were conducted to study the possibility of a nuclear weapon detonation during an accident. On July 26, 1957, a safety experiment, Pascal-A , was detonated in an unstemmed hole at the Nevada Test Site, becoming the first underground shaft nuclear test. The knowledge gained provided data to prevent nuclear yields in case of accidental detonations—for example, in

1264-574: Is paleoseismology . A recording of Earth motion as a function of time, created by a seismograph is called a seismogram . A seismologist is a scientist works in basic or applied seismology. Scholarly interest in earthquakes can be traced back to antiquity. Early speculations on the natural causes of earthquakes were included in the writings of Thales of Miletus ( c.  585 BCE ), Anaximenes of Miletus ( c.  550 BCE ), Aristotle ( c.  340 BCE ), and Zhang Heng (132 CE). In 132 CE, Zhang Heng of China's Han dynasty designed

1343-538: Is called a seismograph . Networks of seismographs continuously record ground motions around the world to facilitate the monitoring and analysis of global earthquakes and other sources of seismic activity. Rapid location of earthquakes makes tsunami warnings possible because seismic waves travel considerably faster than tsunami waves. Seismometers also record signals from non-earthquake sources ranging from explosions (nuclear and chemical), to local noise from wind or anthropogenic activities, to incessant signals generated at

1422-413: Is possible that 5–6 Mw earthquakes described in the historical record could be larger events occurring elsewhere that were felt moderately in the populated areas that produced written records. Documentation in the historic period may be sparse or incomplete, and not give a full picture of the geographic scope of an earthquake, or the historical record may only have earthquake records spanning a few centuries,

1501-573: Is the scientific study of earthquakes (or generally, quakes ) and the generation and propagation of elastic waves through the Earth or other planetary bodies . It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial , oceanic microseism , atmospheric, and artificial processes such as explosions and human activities . A related field that uses geology to infer information regarding past earthquakes

1580-488: Is very unlikely to develop significant nuclear innovations without testing. One other approach is to use supercomputers to conduct "virtual" testing, but codes need to be validated against test data. There have been many attempts to limit the number and size of nuclear tests; the most far-reaching is the Comprehensive Test Ban Treaty of 1996, which has not, as of 2013 , been ratified by eight of

1659-543: The Priscilla shot from Operation Plumbbob in 1957. As a consequence publications including official government documents have the photo mislabeled. The shots can be told apart by the trails of test rockets, which are prominently featured in images and footage of Grable , but appear almost completely absent at the actual Priscilla shot. In 1956, Robert Brownlee, from Los Alamos National Laboratory in New Mexico ,

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1738-454: The VAN method . Most seismologists do not believe that a system to provide timely warnings for individual earthquakes has yet been developed, and many believe that such a system would be unlikely to give useful warning of impending seismic events. However, more general forecasts routinely predict seismic hazard . Such forecasts estimate the probability of an earthquake of a particular size affecting

1817-524: The Vela incident . From the first nuclear test in 1945 until tests by Pakistan in 1998, there was never a period of more than 22 months with no nuclear testing. June 1998 to October 2006 was the longest period since 1945 with no acknowledged nuclear tests. A summary table of all the nuclear testing that has happened since 1945 is here: Worldwide nuclear testing counts and summary . While nuclear weapons testing did not produce scenarios like nuclear winter as

1896-479: The thermal radiation . As shown and reported in the PBS documentary Dark Circle , the pigs survived, but with third-degree burns to 80% of their bodies. Other pigs were placed in pens behind large sheets of glass at measured distances from the hypocenter to test the effects of flying debris on living targets. Studies were conducted of radioactive contamination and fallout from a simulated accidental detonation of

1975-537: The " Annex 2 countries " required for it to take effect, including the United States. Nuclear testing has since become a controversial issue in the United States, with a number of politicians saying that future testing might be necessary to maintain the aging warheads from the Cold War . Because nuclear testing is seen as furthering nuclear arms development, many are opposed to future testing as an acceleration of

2054-518: The "Moho discontinuity" or the " Moho ," it is the boundary between the Earth 's crust and the mantle . It is defined by the distinct change in velocity of seismological waves as they pass through changing densities of rock. In 1910, after studying the April 1906 San Francisco earthquake , Harry Fielding Reid put forward the " elastic rebound theory " which remains the foundation for modern tectonic studies. The development of this theory depended on

2133-539: The CTBT has been signed by 183 States, of which 157 have also ratified. However, for the Treaty to enter into force it needs to be ratified by 44 specific nuclear technology-holder countries. These "Annex 2 States" participated in the negotiations on the CTBT between 1994 and 1996 and possessed nuclear power or research reactors at that time. The ratification of eight Annex 2 states is still missing: China, Egypt, Iran, Israel and

2212-600: The Japanese food supply. Castle Bravo was the worst U.S. nuclear accident, but many of its component problems—unpredictably large yields, changing weather patterns, unexpected fallout contamination of populations and the food supply—occurred during other atmospheric nuclear weapons tests by other countries as well. Concerns over worldwide fallout rates eventually led to the Partial Test Ban Treaty in 1963, which limited signatories to underground testing. Not all countries stopped atmospheric testing, but because

2291-701: The Partial Nuclear Test Ban Treaty. The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions everywhere, including underground. For that purpose, the Preparatory Commission of the Comprehensive Nuclear-Test-Ban Treaty Organization is building an international monitoring system with 337 facilities located all over the globe. 85% of these facilities are already operational. As of May 2012 ,

2370-955: The United Kingdom until 1991, the United States until 1992, and both China and France until 1996. In signing the Comprehensive Nuclear-Test-Ban Treaty in 1996, these countries pledged to discontinue all nuclear testing; the treaty has not yet entered into force because of its failure to be ratified by eight countries. Non-signatories India and Pakistan last tested nuclear weapons in 1998. North Korea conducted nuclear tests in 2006 , 2009 , 2013 , January 2016 , September 2016 and 2017. The most recent confirmed nuclear test occurred in September 2017 in North Korea. Nuclear weapons tests have historically been divided into four categories reflecting

2449-622: The United States and the Soviet Union were responsible for roughly 86% of all nuclear tests, their compliance cut the overall level substantially. France continued atmospheric testing until 1974, and China until 1980. A tacit moratorium on testing was in effect from 1958 to 1961 and ended with a series of Soviet tests in late 1961, including the Tsar Bomba , the largest nuclear weapon ever tested. The United States responded in 1962 with Operation Dominic , involving dozens of tests, including

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2528-457: The United States have signed but not ratified the Treaty; India, North Korea and Pakistan have not signed it. The following is a list of the treaties applicable to nuclear testing: Over 500 atmospheric nuclear weapons tests were conducted at various sites around the world from 1945 to 1980. As public awareness and concern mounted over the possible health hazards associated with exposure to the nuclear fallout , various studies were done to assess

2607-409: The amount of it that is necessary. Hydronuclear tests study nuclear materials under the conditions of explosive shock compression. They can create subcritical conditions, or supercritical conditions with yields ranging from negligible all the way up to a substantial fraction of full weapon yield. Critical mass experiments determine the quantity of fissile material required for criticality with

2686-417: The arms race. In total nuclear test megatonnage , from 1945 to 1992, 520 atmospheric nuclear explosions (including eight underwater) were conducted with a total yield of 545 megatons , with a peak occurring in 1961–1962, when 340 megatons were detonated in the atmosphere by the United States and Soviet Union , while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992

2765-607: The behaviour and causation of earthquakes. The earliest responses include work by John Bevis (1757) and John Michell (1761). Michell determined that earthquakes originate within the Earth and were waves of movement caused by "shifting masses of rock miles below the surface". In response to a series of earthquakes near Comrie in Scotland in 1839, a committee was formed in the United Kingdom in order to produce better detection methods for earthquakes. The outcome of this

2844-621: The blast, which took place at between 18,500 and 20,000 feet (5,600 and 6,100 m) altitude, with the idea of demonstrating the possibility of the use of the weapon over civilian populations without ill effects. The five officers were Colonel Sidney C. Bruce, later professor of Electrical Engineering at Colorado University, died in 2005; Lieutenant Colonel Frank P. Ball, died in 2003; Major John W. Hughes II, died in 1990; Major Norman B. Bodinger, died in 1997; Major Donald A. Luttrell, died in 2014. The videographer, Akira "George" Yoshitake, died in 2013. The Rainier shot, conducted September 19, 1957,

2923-482: The burial points of all explosive devices can be connected by segments of straight lines, each of them connecting two burial points, and the total length does not exceed 40 kilometers. For nuclear weapon tests, a salvo is defined as two or more underground nuclear explosions conducted at a test site within an area delineated by a circle having a diameter of two kilometers and conducted within a total period of time of 0.1 seconds. The USSR has exploded up to eight devices in

3002-542: The considerable progress of earlier independent streams of work on the behavior of elastic materials and in mathematics. An early scientific study of aftershocks from a destructive earthquake came after the January 1920 Xalapa earthquake . An 80 kg (180 lb) Wiechert seismograph was brought to the Mexican city of Xalapa by rail after the earthquake. The instrument was deployed to record its aftershocks. Data from

3081-474: The development of warheads for intercontinental and intermediate range missiles , they also tested air defense and anti-submarine warheads with smaller yields. They included 43 military effects tests on civil and military structures, radiation and bio-medical studies, and aircraft structural tests. Operation Plumbbob had the tallest tower tests to date in the U.S. nuclear testing program as well as high-altitude balloon tests. One nuclear test involved

3160-512: The earth to a resolution of several hundred kilometers. This has enabled scientists to identify convection cells and other large-scale features such as the large low-shear-velocity provinces near the core–mantle boundary . Forecasting a probable timing, location, magnitude and other important features of a forthcoming seismic event is called earthquake prediction . Various attempts have been made by seismologists and others to create effective systems for precise earthquake predictions, including

3239-719: The explosion of a missile launched from a submarine. Almost all new nuclear powers have announced their possession of nuclear weapons with a nuclear test. The only acknowledged nuclear power that claims never to have conducted a test was South Africa (although see Vela incident ), which has since dismantled all of its weapons. Israel is widely thought to possess a sizable nuclear arsenal, though it has never tested, unless they were involved in Vela. Experts disagree on whether states can have reliable nuclear arsenals—especially ones using advanced warhead designs, such as hydrogen bombs and miniaturized weapons—without testing, though all agree that it

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3318-441: The explosion's effects, it did not give an appreciable understanding of nuclear fallout , which was not well understood by the project scientists until well after the atomic bombings of Hiroshima and Nagasaki . The United States conducted six atomic tests before the Soviet Union developed their first atomic bomb ( RDS-1 ) and tested it on August 29, 1949. Neither country had very many atomic weapons to spare at first, and so testing

3397-514: The explosion, combined with the specific design of the shaft, could accelerate the plate to approximately six times Earth's escape velocity . Nuclear testing The first nuclear device was detonated as a test by the United States at the Trinity site in New Mexico on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT . The first thermonuclear weapon technology test of an engineered device, codenamed Ivy Mike ,

3476-405: The extent of the hazard. A Centers for Disease Control and Prevention / National Cancer Institute study claims that nuclear fallout might have led to approximately 11,000 excess deaths, most caused by thyroid cancer linked to exposure to iodine-131 . The following list is of milestone nuclear explosions. In addition to the atomic bombings of Hiroshima and Nagasaki , the first nuclear test of

3555-456: The first attempts at the scientific study of earthquakes followed the 1755 Lisbon earthquake. Other notable earthquakes that spurred major advancements in the science of seismology include the 1857 Basilicata earthquake , the 1906 San Francisco earthquake, the 1964 Alaska earthquake , the 2004 Sumatra-Andaman earthquake , and the 2011 Great East Japan earthquake . Seismic waves produced by explosions or vibrating controlled sources are one of

3634-586: The first known seismoscope . In the 17th century, Athanasius Kircher argued that earthquakes were caused by the movement of fire within a system of channels inside the Earth. Martin Lister (1638–1712) and Nicolas Lemery (1645–1715) proposed that earthquakes were caused by chemical explosions within the Earth. The Lisbon earthquake of 1755 , coinciding with the general flowering of science in Europe , set in motion intensified scientific attempts to understand

3713-415: The first waves to appear on a seismogram as they are the fastest moving waves through solids. S-waves are transverse waves that move perpendicular to the direction of propagation. S-waves are slower than P-waves. Therefore, they appear later than P-waves on a seismogram. Fluids cannot support transverse elastic waves because of their low shear strength, so S-waves only travel in solids. Surface waves are

3792-552: The formation of these treaties. Examples can be seen in the following articles: The Partial Nuclear Test Ban treaty makes it illegal to detonate any nuclear explosion anywhere except underground, in order to reduce atmospheric fallout. Most countries have signed and ratified the Partial Nuclear Test Ban, which went into effect in October 1963. Of the nuclear states, France, China, and North Korea have never signed

3871-477: The foundation of modern instrumental seismology and carried out seismological experiments using explosives. He is also responsible for coining the word "seismology." In 1889 Ernst von Rebeur-Paschwitz recorded the first teleseismic earthquake signal (an earthquake in Japan recorded at Pottsdam Germany). In 1897, Emil Wiechert 's theoretical calculations led him to conclude that the Earth's interior consists of

3950-432: The global seismographic monitoring has been for the detection and study of nuclear testing . Because seismic waves commonly propagate efficiently as they interact with the internal structure of the Earth, they provide high-resolution noninvasive methods for studying the planet's interior. One of the earliest important discoveries (suggested by Richard Dixon Oldham in 1906 and definitively shown by Harold Jeffreys in 1926)

4029-406: The interior of the materials; surface waves that travel along surfaces or interfaces between materials; and normal modes , a form of standing wave. There are two types of body waves, pressure waves or primary waves (P-waves) and shear or secondary waves ( S waves ). P-waves are longitudinal waves that involve compression and expansion in the direction that the wave is moving and are always

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4108-491: The lack of creation of a critical mass of fissile material. They are the only type of tests allowed under the interpretation of the Comprehensive Nuclear-Test-Ban Treaty tacitly agreed to by the major atomic powers. Subcritical tests continue to be performed by the United States, Russia, and the People's Republic of China, at least. Subcritical tests executed by the United States include: The first atomic weapons test

4187-764: The largest troop maneuver ever associated with U.S. nuclear testing. Approximately 18,000 members of the U.S. Air Force , Army , Navy and Marines participated in exercises Desert Rock VII and VIII during Operation Plumbbob. The military was interested in knowing how the average foot-soldier would stand up, physically and psychologically, to the rigors of the tactical nuclear battlefield . Almost 1,200 pigs were subjected to bio-medical experiments and blast-effects studies during Operation Plumbbob. On shot Priscilla (37 kt), 719 pigs were used in various experiments on Frenchman Flat . Some pigs were placed in elevated cages and provided with suits made of different materials, to test which materials provided best protection from

4266-409: The later phases of the Cold War , though, both countries developed accelerated testing programs, testing many hundreds of bombs over the last half of the 20th century. Atomic and nuclear tests can involve many hazards. Some of these were illustrated in the U.S. Castle Bravo test in 1954. The weapon design tested was a new form of hydrogen bomb, and the scientists underestimated how vigorously some of

4345-455: The medium or location of the test. Another way to classify nuclear tests is by the number of explosions that constitute the test. The treaty definition of a salvo test is: In conformity with treaties between the United States and the Soviet Union, a salvo is defined, for multiple explosions for peaceful purposes, as two or more separate explosions where a period of time between successive individual explosions does not exceed 5 seconds and where

4424-520: The military effects of atomic weapons ( Crossroads had involved the effect of atomic weapons on a navy, and how they functioned underwater) and to test new weapon designs. During the 1950s, these included new hydrogen bomb designs, which were tested in the Pacific, and also new and improved fission weapon designs. The Soviet Union also began testing on a limited scale, primarily in Kazakhstan . During

4503-481: The ocean floor and coasts induced by ocean waves (the global microseism ), to cryospheric events associated with large icebergs and glaciers. Above-ocean meteor strikes with energies as high as 4.2 × 10 J (equivalent to that released by an explosion of ten kilotons of TNT) have been recorded by seismographs, as have a number of industrial accidents and terrorist bombs and events (a field of study referred to as forensic seismology ). A major long-term motivation for

4582-436: The ocean processes responsible for the global background seismic microseism . By the 1960s, Earth science had developed to the point where a comprehensive theory of the causation of seismic events and geodetic motions had come together in the now well-established theory of plate tectonics . Seismic waves are elastic waves that propagate in solid or fluid materials. They can be divided into body waves that travel through

4661-481: The primary methods of underground exploration in geophysics (in addition to many different electromagnetic methods such as induced polarization and magnetotellurics ). Controlled-source seismology has been used to map salt domes , anticlines and other geologic traps in petroleum -bearing rocks , faults , rock types, and long-buried giant meteor craters . For example, the Chicxulub Crater , which

4740-528: The purpose of the test itself. Aside from these technical considerations, tests have been conducted for political and training purposes, and can often serve multiple purposes. Computer simulation is used extensively to provide as much information as possible without physical testing. Mathematical models for such simulation model scenarios not only of performance but also of shelf life and maintenance . A theme has generally been that even though simulations cannot fully replace physical testing, they can reduce

4819-400: The result of P- and S-waves interacting with the surface of the Earth. These waves are dispersive , meaning that different frequencies have different velocities. The two main surface wave types are Rayleigh waves , which have both compressional and shear motions, and Love waves , which are purely shear. Rayleigh waves result from the interaction of P-waves and vertically polarized S-waves with

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4898-416: The seismograph would eventually determine that the mainshock was produced along a shallow crustal fault. In 1926, Harold Jeffreys was the first to claim, based on his study of earthquake waves, that below the mantle, the core of the Earth is liquid. In 1937, Inge Lehmann determined that within Earth's liquid outer core there is a solid inner core . In 1950, Michael S. Longuet-Higgins elucidated

4977-476: The surface and can exist in any solid medium. Love waves are formed by horizontally polarized S-waves interacting with the surface, and can only exist if there is a change in the elastic properties with depth in a solid medium, which is always the case in seismological applications. Surface waves travel more slowly than P-waves and S-waves because they are the result of these waves traveling along indirect paths to interact with Earth's surface. Because they travel along

5056-399: The surface of the Earth, their energy decays less rapidly than body waves (1/distance vs. 1/distance ), and thus the shaking caused by surface waves is generally stronger than that of body waves, and the primary surface waves are often thus the largest signals on earthquake seismograms . Surface waves are strongly excited when their source is close to the surface, as in a shallow earthquake or

5135-511: The then four nuclear states and many non-nuclear states signed the Limited Test Ban Treaty , pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space . The treaty permitted underground nuclear testing . France continued atmospheric testing until 1974, and China continued until 1980. Neither has signed the treaty. Underground tests conducted by the Soviet Union continued until 1990,

5214-455: The weapon materials would react. As a result, the explosion—with a yield of 15 Mt —was over twice what was predicted. Aside from this problem, the weapon also generated a large amount of radioactive nuclear fallout , more than had been anticipated, and a change in the weather pattern caused the fallout to spread in a direction not cleared in advance. The fallout plume spread high levels of radiation for over 100 miles (160 km), contaminating

5293-493: Was 1,352 explosions with a total yield of 90 Mt. The yields of atomic bombs and thermonuclear are typically measured in different amounts. Thermonuclear bombs can be hundreds or thousands of times stronger than their atomic counterparts. Due to this, thermonuclear bombs' yields are usually expressed in megatons which is about the equivalent of 1,000,000 tons of TNT. In contrast, atomic bombs' yields are typically measured in kilotons, or about 1,000 tons of TNT. In US context, it

5372-467: Was asked to examine whether nuclear detonations could be conducted underground. The first subterranean test was the nuclear device known as Pascal A, which was lowered down a 500 ft (150 m) borehole. However, the detonated yield turned out to be 50,000 times greater than anticipated, creating a jet of fire that shot hundreds of meters into the sky. During the Pascal-B nuclear test of August 1957,

5451-591: Was caused by an impact that has been implicated in the extinction of the dinosaurs , was localized to Central America by analyzing ejecta in the Cretaceous–Paleogene boundary , and then physically proven to exist using seismic maps from oil exploration . Seismometers are sensors that detect and record the motion of the Earth arising from elastic waves. Seismometers may be deployed at the Earth's surface, in shallow vaults, in boreholes, or underwater . A complete instrument package that records seismic signals

5530-481: Was conducted near Alamogordo, New Mexico, on July 16, 1945, during the Manhattan Project , and given the codename " Trinity ". The test was originally to confirm that the implosion-type nuclear weapon design was feasible, and to give an idea of what the actual size and effects of a nuclear explosion would be before they were used in combat against Japan. While the test gave a good approximation of many of

5609-827: Was decided during the Manhattan Project that yield measured in tons of TNT equivalent could be imprecise. This comes from the range of experimental values of the energy content of TNT, ranging from 900 to 1,100 calories per gram (3,800 to 4,600 kJ/g). There is also the issue of which ton to use, as short tons, long tons, and metric tonnes all have different values. It was therefore decided that one kiloton would be equivalent to 1.0 × 10 calories (4.2 × 10  kJ). The nuclear powers have conducted more than 2,000 nuclear test explosions (numbers are approximate, as some test results have been disputed): There may also have been at least three alleged but unacknowledged nuclear explosions (see list of alleged nuclear tests ) including

5688-416: Was focused on the borehole because studying the velocity of the plate was deemed scientifically interesting. After the detonation, the plate appeared in only one frame. Regarding its speed Brownlee reckoned that "a lower limit could be calculated by considering the time between frames (and I don't remember what that was)", and joked that the best estimate was it was "going like a bat !". Brownlee estimated that

5767-720: Was one of the main drivers for the ban of nuclear weapons testing, particularly atmospheric testing. It has been estimated that by 2020 up to 2.4 million people have died as a result of nuclear weapons testing. There are many existing anti-nuclear explosion treaties, notably the Partial Nuclear Test Ban Treaty and the Comprehensive Nuclear Test Ban Treaty . These treaties were proposed in response to growing international concerns about environmental damage among other risks. Nuclear testing involving humans also contributed to

5846-509: Was relatively infrequent (when the U.S. used two weapons for Operation Crossroads in 1946, they were detonating over 20% of their current arsenal). However, by the 1950s the United States had established a dedicated test site on its own territory ( Nevada Test Site ) and was also using a site in the Marshall Islands ( Pacific Proving Grounds ) for extensive atomic and nuclear testing. The early tests were used primarily to discern

5925-576: Was tested at the Enewetak Atoll in the Marshall Islands on November 1, 1952 (local date), also by the United States. The largest nuclear weapon ever tested was the Tsar Bomba of the Soviet Union at Novaya Zemlya on October 30, 1961, with the largest yield ever seen, an estimated 50–58 megatons . With the advent of nuclear technology and its increasing impact an anti-nuclear movement formed and in 1963, three (UK, US, Soviet Union) of

6004-409: Was that the outer core of the earth is liquid. Since S-waves do not pass through liquids, the liquid core causes a "shadow" on the side of the planet opposite the earthquake where no direct S-waves are observed. In addition, P-waves travel much slower through the outer core than the mantle. Processing readings from many seismometers using seismic tomography , seismologists have mapped the mantle of

6083-410: Was the first fully contained underground nuclear test, meaning that no fission products were vented into the atmosphere. This test of 1.7 kt could be detected around the world by seismologists using ordinary seismic instruments. The Rainier test became the prototype for larger and more powerful underground tests. Images from Upshot-Knothole Grable were accidentally relabeled as belonging to

6162-415: Was the production of one of the first modern seismometers by James David Forbes , first presented in a report by David Milne-Home in 1842. This seismometer was an inverted pendulum, which recorded the measurements of seismic activity through the use of a pencil placed on paper above the pendulum. The designs provided did not prove effective, according to Milne's reports. From 1857, Robert Mallet laid

6241-741: Was widely seen in Italy and abroad as being for failing to predict the earthquake and drew condemnation from the American Association for the Advancement of Science and the American Geophysical Union . However, the magazine also indicated that the population of Aquila do not consider the failure to predict the earthquake to be the reason for the indictment, but rather the alleged failure of the scientists to evaluate and communicate risk. The indictment claims that, at

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