Silencing the Bomb Read online

  Many earthquakes deeper than about 30 to 45 miles (50 to 75 km) could be identified using the seismic wave pP, which arrives soon after the P wave and is reflected from the surface of the Earth near the earthquake source (figure 3.1). These included deeper earthquakes beneath the Kuril-Kamchatka region, the most active area of the USSR, and those beneath the Hindu Kush and Pamir mountains of Central Asia. Shallower earthquakes are often difficult to identify using pP waves because they arrive very soon after P waves.

  FIGURE 3.1

  Interior of the Earth. Lines with arrows indicate paths of seismic waves between a source, such as an earthquake, and a recording station. The epicenter is the point on Earth’s surface directly above the hypocenter of an event.

  Source: Sykes and Evernden, 1982.

  When the Conference of Experts met in August 1958, all nuclear tests had been conducted either in the atmosphere or underwater with the exception of a single very small U.S. underground explosion code-named Rainier. It was detonated in a volcanic rock called tuff during September 1957 at the Nevada Test Site, which had opened in 1951. Its yield of 1.7 kilotons was about ten times smaller than the nuclear explosions of 1945 and ten thousand times smaller than the largest hydrogen bombs tested as of 1958.

  U.S. government scientists twice reduced their estimate of Rainier’s seismic magnitude because stations at different distances gave different results. Many people contested the idea that the 1957 test was difficult to detect seismically and that its signals were hard to distinguish from those of earthquakes. The USSR did not detonate an underground test until October 1961. It was of similar size to Rainier and was likely detonated at the Eastern Kazakhstan test site in much harder rock than Rainier. It was well detected outside the USSR.

  Throughout 1958, both the Soviets and Americans set off many nuclear explosions. The Soviet Union conducted nuclear tests in the atmosphere from February until November 3, 1958. Several were probably in the megaton range. The United States conducted a series of nuclear explosions in the Pacific, called Operation Hardtack I, starting in April 1958. It consisted of atmospheric explosions with yields ranging from a few kilotons to about 10 megatons (10,000 kt) and two underwater shots. Testing ended in August 1958 with two high-altitude nuclear explosions with yields of 3.8 megatons near Johnston Island in the Pacific, which produced radio blackouts and observable effects in the Pacific similar to northern lights.

  The United States conducted additional nuclear explosions in the atmosphere at the Nevada Test Site in September and October 1958 as part of Operation Hardtack II, which also included underground tests of Logan at 5 kilotons, Blanca with a yield of 22 kilotons, and several explosions smaller than one kiloton.

  Upon completion of the Experts’ Report at the end of their conference on August 22, 1958, President Eisenhower proposed a one-year testing moratorium on all testing if the Soviet Union also refrained. This moratorium would be extended on a year-by-year basis if the control system recommended by the Experts could be installed and progress made on arms control agreements. While a treaty was being negotiated, both the Soviet Union and the United States continued to conduct nuclear tests into the fall of 1958.

  Treaty negotiations, called the Conference on the Discontinuance of Nuclear Tests, began in Geneva on October 31, 1958, a day after the Blanca explosion by the United States. Parties to the conference consisted of the three nuclear states at the time—the United States, the United Kingdom, and the Soviet Union.

  The USSR’s second underground nuclear test did not occur until February 1962. It took place at its Eastern Kazakhstan test site with a yield comparable to that of the U.S. test Blanca. Because most of Russia consists of areas of old geologic units that favor very good propagation of seismic waves, the United States overestimated the yields of underground nuclear explosions at the two main Soviet test sites, including those of 1961 and 1962, by a factor of about three times and continued to do so for decades.

  The United States calibrated unknown Soviet yields from their measured seismic magnitudes using measured yields and magnitudes of underground nuclear explosions in Nevada and southern Algeria. This turned out to be a big mistake that led to the large overestimations of Soviet yields. The Soviet Union did know, however, that seismic waves propagated efficiently in various parts of their country from its earlier large chemical explosions.

  U.S. REASSESSMENT OF DIFFICULTIES WITH VERIFICATION IN 1959

  A key factor in the U.S. reluctance to negotiate a treaty was that U.S. Department of Defense officials and others were not convinced about the reliability of identifying nuclear explosions of moderate and small size. They argued that seismic signals from underground explosions based on 1958 data were both smaller and harder to distinguish from the signals of earthquakes of comparable size than the forecasts of the Experts in August 1958.

  After reviews within the U.S. government, these new findings from underground explosions in 1958 were tabled as negotiations resumed in Geneva in January 1959. The White House issued a public statement about the new findings and their implications. Because some of the best seismic data and information for the underground explosions in Nevada in 1958 were classified, it was difficult, however, for most seismologists to form independent judgments about the identification of small nuclear explosions.

  The relevance of the new U.S. data on underground explosions was strongly challenged by Soviet geophysicists Y. Riznichenko and Leonid Brekhovskikh in an article in Pravda on January 20, 1959. The Soviet ambassador to the conference stated that the Experts’ report of the previous summer should be the sole technical basis for the negotiations. The U.S. ambassador to the Geneva talks insisted that the new data must be considered. He also proposed a technical meeting to discuss detection of high-altitude nuclear explosions.

  The Eisenhower administration formed a Panel on Seismic Improvement, consisting of U.S. seismologists and other experts, that was chaired by Lloyd Berkner, president of Associated Universities. Known as the Berkner Panel, its initial assignment was to ascertain if improvements could be made to the monitoring stations proposed by the Experts so that the number of problem seismic events per year being considered would not have to be increased. Their main task was to resolve the difficulties in identifying underground explosions and distinguishing their seismic signals from those of earthquakes.

  The findings of the Berkner Panel were introduced at the Geneva conference in June 1959. Their recommended improvements consisted of greater numbers of seismic sensors at each control post, the use of seismic surface waves for discriminating earthquakes from explosions, and the placing of unmanned instruments, so-called black boxes, in earthquake-prone areas of the USSR and the United States. The black boxes would be designed to be tamper proof.

  SEISMIC MAGNITUDES USED TO DESCRIBE THE SIZES OF EARTHQUAKES AND UNDERGROUND NUCLEAR EXPLOSIONS

  It is necessary to have a simple way to describe the sizes of earthquakes. Seismologists use many different magnitude scales to do this. They all involve measuring the amplitude, or size, of a particular seismic wave, taking the logarithm of its amplitude, and making a correction for the distance between the source and a seismic station. Logarithms are used because the sizes of seismic waves vary over a huge range. Because magnitude scales are logarithmic, magnitude increases one unit when amplitude increases ten times. Hence, an earthquake of magnitude 6 is ten times larger in amplitude than an event of magnitude 5. In 1935, Charles Richter at Cal Tech devised the original magnitude scale, called ML or Richter magnitude, for local earthquakes in southern California. The magnitudes listed in table 3.2 are not those proposed by Richter but ones appropriate for events at large distances.

  TABLE 3.2 Earthquake Magnitudes

  mb Determined from the amplitudes of short-period seismic P waves, usually at distances greater than about 1250 miles (2000 km)

  Ms Determined from the amplitudes of long-period seismic surface waves

  mbLg Determined from the amplitudes of seismic waves at region
al distances (less than 1250 miles or 2000 km) within continents

  Mw Determined from very long-period (low-frequency) seismic waves; called moment magnitude

  In describing underground nuclear explosions and earthquakes, the United States advocated the use of the seismic magnitude mb, which could be measured from P-waves on seismograms, whereas explosive energy or yield could not be measured directly. Energy is a physical quantity, whereas seismic magnitude is not.

  FURTHER PROPOSALS BY THE EISENHOWER ADMINISTRATION

  In the 1959 negotiations, the United States also emphasized that methods could be used to mask or reduce the sizes of seismic waves from nuclear tests. Disagreements with the Soviet Union about evasion and the determination of seismic magnitudes were a complete nonstarter for the remainder of the talks with the USSR through 1963.

  In April 1959, Eisenhower proposed a phased approach to achieving a comprehensive nuclear test ban. He stated that Soviet proposals did not provide for effective control (i.e., verification) and recommended starting with a ban on nuclear tests in the atmosphere. The proposal was endorsed by British prime minister Macmillan and, with some further modifications, was accepted by Soviet premier Nikita Khrushchev. This made it likely that a test ban treaty could be signed at the Paris summit that both President Eisenhower and Premier Khrushchev agreed to attend in May 1960.

  The downing of an American U-2 spy plane over the Soviet Union on May 1, however, led to an atmosphere of hostility that cut short the Paris summit and the chance for a test ban during the remainder of Eisenhower’s presidency. Glen Seaborg, the discoverer of plutonium for which he won the Noble Prize, a chairman of the Atomic Energy Commission, and an adviser to ten U.S. presidents, was known for daily entries in his diary. In his 1981 book he wrote, “President Eisenhower, alarmed by the increased tensions, was reported to have decided to order the resumption of testing if Richard Nixon won the election” [in November 1960]. After Kennedy’s victory, he advised the president-elect “to resume testing without delay.”

  The Geneva conference recessed in December 1959 with each of the three parties submitting annexes about the verification of underground testing. Because the Soviet annex differed considerably from those of the United States and Britain, a considerable impasse existed. Negotiations resumed in January 1960 with proposals for annual quotas on the number of on-site inspections and a threshold ban on underground testing, which was to prohibit large underground tests. The United States proposed a seismic magnitude threshold of 4.75, about 15 to 20 kilotons. This conversion of magnitude to yield was based solely on a few underground tests in 1957 and 1958 in Nevada in tuff, a soft rock. A magnitude mb of 4.75 corresponds to smaller nuclear explosions at the two main Soviet test sites.

  The USSR declared a moratorium on nuclear testing after completing a large series of nuclear tests in November 1958. Likewise, the United States followed its own self-declared moratorium after completing the Hardtack tests in October 1958. Neither country is known to have tested nuclear explosions for nearly three years. One exception is that the United States conducted explosions in secret with tiny nuclear yields equivalent to the explosive power of only several pounds (kilograms) of TNT. Called hydronuclear, these explosions confirmed that U.S. weapons were “one-point safe”—that is, a sudden shock at one point on their surface would not lead to a large inadvertent nuclear explosion.

  In the meantime, France conducted its first nuclear test in Algeria in February 1960. The Soviet Union stated that the United States could obtain information about the development of nuclear weapons from the French even if the United States was observing a moratorium. This provided an excuse when the USSR resumed nuclear testing in September 1961.

  SOVIET SERIES OF LARGE NUCLEAR TESTS IN 1961 AND 1962

  The Soviet Union suddenly ended its self-declared moratorium on testing, detonating a huge series of nuclear explosions starting on September 1, 1961. The previous day, it announced that it would resume testing. It came at the height of the Berlin crisis, when the Soviet Union attempted to block western access to that city and the United States flew in supplies. Several tests were in the megaton range, and about six were 10 to 30 megatons. Numerous Soviet tests, most of them in the atmosphere, continued until December 25, 1962.

  The Russians also detonated the largest nuclear explosion ever conducted at their Arctic test site near the islands of Novaya Zemlya on October 30, 1961. Premier Khrushchev announced it ahead of time. The explosion occurred in the atmosphere with a yield of about 42 to 50 megatons, more than three thousand times the power of the Hiroshima bomb of 1945 (figure 3.2). It is often called either “the Tsar bomb” or “Big Ivan.”

  FIGURE 3.2

  Yields of key nuclear explosions detonated by the Soviet Union and the United States in the atmosphere and underground. Size or yield of nuclear explosions is in kilotons (kt).

  Unpublished figure by the author.

  Its detonation certainly scared the United States government. Soviet nuclear scientists later said it was never weaponized; it was one of a kind and was not mass-produced for delivery by airplanes or missiles. In fact, the development of new nuclear weapons in the mid-1960s to the mid-1970s involved yields smaller than several megatons for single-warhead missiles and yields smaller than a megaton for missiles with multiple warheads.

  The Soviet resumption of nuclear testing caught the United States by surprise. The many tests must have been planned well in advance. Some people in the United States accused the Soviet Union of cheating by preparing to test while negotiations were in progress in Geneva. Both sides, however, were following self-declared moratoria at the time, not treaties, protocols, or other agreements of indefinite duration. Nevertheless, it contributed to a U.S. view that the Russians could not be trusted.

  President Kennedy ordered the resumption of nuclear testing by the United States on September 5, 1961; explosions commenced in Nevada ten days later. The United States and the United Kingdom started testing at Christmas Island in the Pacific in April 1962 and then at Johnston Island.

  In 1957 the Soviet Union used a large missile to launch a satellite called Sputnik. Its success was followed by the failure of a U.S. rocket launched from the ground that was to deploy a satellite. This led to apprehension in the United States that the USSR was ahead in the development of intercontinental ballistic missiles (ICBMs) that could carry nuclear weapons.

  President Eisenhower, however, was well aware of the secret development of military ICBMs by the United States, but he did not publicly divulge its existence. Kennedy ran for election as president in 1960 on the claim that a “missile gap” favored the Soviet Union. The apparent gap disappeared soon after Kennedy became president. The United States observed via early satellite imagery that the Soviet Union possessed fewer ICBMs than was claimed. The United States was, in fact, ahead in deployed ICBMs.

  THE CUBAN MISSILE CRISIS

  The world came the closest it has come thus far to nuclear war during the Cuban Missile Crisis of October 1962. An American U-2 spy plane secretly photographed nuclear missile sites being built in Cuba by the Soviet Union. Decades later senior Soviet military officials revealed that their commanders in Cuba had been authorized to launch medium-range SS-4 ballistic missiles at the United States if the United States attacked the Russian sites in Cuba. The SS-4’s carried nuclear weapons. Khrushchev undertook the installation of missiles in Cuba, apparently regarding Kennedy as young and inexperienced.

  Several high-ranking military officials advised Kennedy to invade Cuba, but fortunately he refrained. Instead, he instituted a U.S. naval blockade to prevent the Soviets from bringing more military equipment and supplies into Cuba. Both Kennedy and Khrushchev recognized the devastating possibility of a nuclear war and publicly agreed to a deal. The Soviets withdrew their nuclear weapons and missiles from Cuba. Under an unannounced part of the agreement, which remained secret for more than twenty-five years, the United States withdrew old Jupiter missiles from Turkey.

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sp; A few months after the crisis, a personal insight came from my father, who was in charge of security at the Washington Air Traffic Control Center. He was responsible for keeping military aircraft separated from civilian flights in their broad area of traffic control. He mentioned to me the huge numbers of military flights over the southeastern United States during the Cuban crisis and said, “You don’t know how close we came to war.”

  THE LIMITED NUCLEAR TEST BAN TREATY OF 1963

  The Cuban Missile Crisis and the fear of nuclear war became a turning point in test ban negotiations. Khrushchev wrote Kennedy in December 1962, “The time has come now to put an end once and for all time to nuclear tests.” He offered three on-site inspections (OSIs) per year. The United States informed Soviet officials in February 1963 that it was willing to reduce its proposed annual quota of OSIs to seven. Many people assumed that a compromise between three and seven OSIs would be easy to achieve and a test ban would follow. Nevertheless, different views in the United States about evasive testing, the effectiveness of monitoring, and the use of seismic magnitudes continued to impede an agreement that would include underground tests.

  A conciliatory speech by Kennedy at American University in June 1963 and Khrushchev’s welcoming of it led to an agreement among the United States, the United Kingdom, and the USSR to hold test ban talks in Moscow. Former ambassador to the Soviet Union W. Averell Harriman led the U.S. delegation. A full CTBT was the U.S. objective. If that was not possible, Harriman was to seek a limited treaty banning nuclear tests in the atmosphere, underwater, and in space. On the opening day of the negotiations in July 1963, the USSR submitted a draft treaty that included those environments but not underground testing. The Soviet Union would accept unmanned “black boxes” on its territory but not on-site inspections. OSIs were considered essential by the United States.