This chapter covers the continuing long debate in the 1980s about determining the yields of Soviet nuclear explosions. During the Reagan and first Bush administrations, the U.S. government charged that the Soviet Union had cheated on the Threshold Test Ban Treaty (TTBT) by testing nuclear weapons above its 150-kiloton limit. The issue of yield determination was finally resolved in 1988 by close-in monitoring of explosions by the United States and the USSR at the other’s test sites. The United States and Russia ratified an amended TTBT, which entered into force in December 1990.
My article “The Verification of a Comprehensive Nuclear Test Ban” with Jack Evernden in the Scientific American of October 1982 drew criticism from DARPA officials for its conclusions about the yields of Soviet explosions, our finding that the Soviet Union had not cheated on the Threshold Treaty, and our claims that a full test ban could be monitored effectively. In the early 1980s, the Nuclear Monitoring Research Office of DARPA included Ralph Alewine, Thomas Bache, Carl Romney, and Alan Ryall, all of whom opposed a full test ban. All very conservative in their views on national security policies, they focused almost entirely on the determination of Soviet yields.
Bache wrote a DARPA report on yield determination in 1982 that stated, for yield estimation with short-period P waves, an important issue is possible bias caused by path effects (my italics). By path effects he meant differences in the absorption (attenuation) of P waves for paths from Soviet explosions in Eastern Kazakhstan compared to those from the Nevada Test Site. When expressed in terms of seismic magnitude, those differences are called magnitude or mb bias, as discussed in the previous chapter.
Bias is a systematic difference, like measuring a length without realizing that an inch has been cut off the measuring stick. Just making additional P-wave measurements of magnitude (akin to measurements of length using a defective ruler) does not decrease the bias. When an average mb is obtained from about a hundred stations, the uncertainty is very small, about 0.04 mb units. To obtain an accurate estimate of the yield of a Soviet explosion from an average value of mb, however, that magnitude still needs to be corrected for bias between it and underground explosions in Nevada. The systematic difference of about 0.3 to 0.4 mb units between those sites dominates the uncertainty in yield determination for Soviet tests. Hence, the main task is to determine that systematic error, not to focus on more or better mb measurements.
Bache also stated, “Regionally varying attenuation [absorption of P waves] is an important potential cause for bias in yield estimates [my italics]. Current knowledge suggests that differences of 0.3 or 0.4 mb for otherwise identical events in different areas can be expected, but it is difficult to demonstrate that they actually occur.”
In April 1983, Larry Burdick, a seismologist at Woodward-Clyde Consultants, wrote to me stating that Bache, his contract monitor, had reviewed Burdick’s report on magnitude bias and said to him, “Your section 2 is a good example of the problems (futility?) associated with estimating a specific site amplitude bias from travel time residuals. Some important people seem to think otherwise. For example note the way Sykes and Evernden use travel time residuals to estimate mb bias of Semipalatinsk [Eastern Kazakhstan] compared to NTS on page 55 of their article in the October Scientific American. I would appreciate your sending a note to Sykes drawing attention to this section in your report.” Burdick then wrote to me, “Since we ultimately use travel times to estimate site bias, we obviously believe that this is a valid approach. I infer that Tom [Bache] believes otherwise.” Since I had read Burdick’s report, Bache was at the very least not very professional in asking Burdick to send me a note citing the errors of our ways.
In 1982 the Reagan administration decided not to submit either the TTBT or its companion Peaceful Nuclear Explosion Treaty (PNET) for ratification by the U.S. Senate until the USSR agreed to additional verification measures. Two years later, in 1984, the administration publicly charged the Soviet Union with a probable violation of the TTBT. This was part of a larger set of accusations that the USSR most likely had cheated on other arms control agreements, including the Anti-Ballistic Missile (ABM) Treaty, encryption of data during missile testing, the number of new missile systems permitted under the second Strategic Arms Limitation Treaty, and the Chemical Weapons Treaty.
Evernden and I had concluded, however, that reports of Soviet cheating on the Threshold Treaty were erroneous. When our calibration was used, it was apparent that none of the Russian weapons tests exceeded the 150-kiloton limit of the TTBT. Several Soviet explosions did come close to that limit, however, as was also the case for some U.S. tests in Nevada.
SYMPOSIUM IN 1983 ON THE VERIFICATION OF TEST BAN TREATIES
Evernden and I organized a symposium for the American Geophysical Union (AGU) on Verification of Nuclear Test Ban Treaties. This symposium, held in Baltimore in June 1983, was intended (1) to present arguments for and against verification of a complete test ban, (2) to assess the determination of yields under the Threshold Treaty, and (3) to address accusations that the Soviet Union had cheated on the TTBT.
About five hundred people attended, including many from U.S. federal agencies. A morning session was devoted to the Threshold Treaty, while the afternoon dealt with monitoring a full nuclear test ban (a CTBT). We invited Bache and Alewine of DARPA to give talks on each, which they did. Of course, Evernden and I knew to expect strong criticisms from them. I obtained a written copy of their unpublished eleven-page presentation, plus nineteen figures, titled “Monitoring a Comprehensive Test Ban Treaty.”
The worst was yet to come from DARPA: an accusation that someone or some agency had leaked the purported revised U.S. classified methodology for determining yields of Soviet explosions to the media. Figure 10.1, from their presentation, showed P-wave magnitudes, mb, of nuclear explosions in Eastern Kazakhstan from the start of the TTBT on April 1, 1976, through 1982. The dates in figure 10.2, from our paper, included that period and extended it back to 1970.
FIGURE 10.1
Seismic magnitudes mb (filled circles) as a function of date for underground nuclear explosions at the Soviet test site in Eastern Kazakhstan.
Source: 1983 presentation by Bache and Alewine of the U.S. Department of Defense, published in Pike and Rich, 1984.
FIGURE 10.2
Seismic magnitudes mb for underground nuclear explosions at Eastern Kazakhstan.
Source: Sykes, Evernden, and Cifuentes, 1983; also published in Pike and Rich, 1984.
The DARPA chart in figure 10.1 was annotated to show 150 kilotons for explosions in Nevada and interpretations of mb values associated with explosions of that yield in Eastern Kazakhstan—pre and post July 1977. It indicated that Soviet tests seemed to double in yield between 1978 and 1979 and claimed this was evidence that the Soviets had discovered U.S. plans to modify its classified yield calibration formula, presumably about July 1977. According to Alewine and Bache, the USSR raised the yields of their tests accordingly. The dotted horizontal line in figure 10.1 indicates (mistakenly) that fourteen Soviet tests after 1978 exceeded the 150-kiloton limit of the TTBT, four of them by a factor of two. Bache and colleagues published a similar figure and arguments again in 1986.
Figure 10.2, which I presented at the 1983 symposium, shows that magnitudes and yields of Soviet tests actually rose gradually over a period of three years and then stabilized at a magnitude mb close to 6.2. Evernden, Cifuentes, and I associated mb 6.2 with a yield of about 150 kilotons, factoring in an mb bias of 0.35 units between hard rock in Eastern Kazakhstan and Nevada.
Figure 10.1 indicates a magnitude of 5.65 for explosions of 150 kilotons in Nevada, but this magnitude is appropriate only for tests in softer rocks, not the much harder rocks in Eastern Kazakhstan. Without taking into account the magnitude bias between the two test sites and the difference in rock types, the inference from the Department of Defense work was that Soviet tests of magnitude 6.2 corresponded to yields of about 600 to 800 kilotons. Evernden and I thought Alewine and Bache were not only incorrect but misleading as well.
After each talk at the 1983 symposium, we devoted about five minutes to questions for the speakers. Alewine received several, including one from me: “Then I have one final question that is to do with the last sentence in your abstract. And there, perhaps to paraphrase you, you liken [sic] yields of 600 to 800 kilotons or larger, and none of the yields you were talking about here [in your oral presentation] are in that range. Could you discuss that?” Alewine replied, “I didn’t have that in the paper.” I replied, “It’s in your [printed] abstract.” Alewine: “Right. Well, what we observed, I think what we said in the paper is that for an mb 6.2 in the U.S. experience, we have not seen an mb 6.2 unless yields were in the 600/800 kiloton range.” Evernden responded, “But that means that the feeling that numerous people got out of the abstract, that you were concluding that possibly the Soviets had tested to 600/800 kilotons, was a false interpretation of your abstract. Is that right?” Alewine: “That’s right.”
In addition, I recalculated magnitudes to three significant figures (6.21, 6.14, etc.) for figure 10.2. It is clear in Department of Defense figure 10.1, however, that the DARPA scientists calculated magnitudes to only two significant figures (6.2, 6.1, etc.). Rounding off magnitudes to two significant figures is sufficient for arguing about a factor of two but not in deciding if a yield was, say, 140, 150, or 160 kilotons.
Table 10.1 lists several quotations from media coverage in 1982 and 1983 claiming that the yields of several Soviet explosions exceeded the 150-kiloton limit of the Threshold Treaty by large amounts. Some of these probably involved leaks to conservative columnists.
TABLE 10.1 Published statements about yields of the largest USSR explosions under the Threshold Test Ban Treaty
| JACK ANDERSON—COLUMN IN WASHINGTON POST, AUGUST 1982 |
| 350 kt |
“…the Soviets appear to have exceeded the 150-kiloton limit at least 11 times since 1978. One test in September 1980 was clocked at a likely size of 350 kilotons, according to my sources.” |
| 260 kt |
“As recently as July 4, the Soviets set off a huge nuclear blast. It was estimated at a likely 260 kilotons,…” |
| HAROLD M. AGNEW—LETTER TO SCIENCE, APRIL 8, 1983 |
| 400 kt |
“…subsequent tests appeared to us to range as high as 400 kilotons…” |
| ALEWINE AND BACHE—EOS, MAY 1983 (ABSTRACT FOR SYMPOSIUM ON JUNE 2) |
| 600–800 kt and larger |
“In U.S. experience an mb greater then 6.2 (as measured for the largest Soviet events) has only been seen for yields of 600–800 kt and larger.” |
| JUDITH MILLER—NEW YORK TIMES, JULY 26, 1982 |
| 300 kt |
“One official said that there had been several Soviet tests, many at one particular site, that had been estimated at 300 kilotons.” |
Source: Sykes and colleagues, 1983.
Why did the United States start testing near 150 kilotons soon after the TTBT became effective, but the Soviet Union did not? The United States knew from previous tests that it could detonate an explosion of 150 kilotons in Nevada without any damage occurring in the nearby cities of Las Vegas and Reno. The Soviets had conducted larger tests than magnitude 6.2 before the TTBT became effective in 1976 at their remote Arctic test site at Novaya Zemlya. If they had been set off in Eastern Kazakhstan, their stronger shaking likely would have caused damage in the nearby city of Semipalatinsk. This may explain the gradual increase in yields over three years (figure 10.2) to ascertain how much damage larger tests would cause in that city.
Soviet explosions larger than about magnitude 6.2 or 150 kilotons might well have produced damage in Semipalatinsk. In 1984 Evernden and I claimed that if a 75-kiloton explosion were set off at the site of the 1964 Salmon explosion in Mississippi, it would have caused damage to nearby towns and cities. Our reasoning was that propagation of seismic waves would be as damaging in Kazakhstan as it would be in Mississippi (or the rest of the central and eastern United States). A recent example of efficient wave propagation and strong shaking can be seen in the damage to the Washington Monument and the National Cathedral in Washington, DC, which was 100 miles (160 km) away from the magnitude 5.8 earthquake near Mineral, Virginia, in August 2011. Soviet explosions in Eastern Kazakhstan of 75 kilotons generated seismic waves of about mb 6.
At the 1983 symposium, Inés Cifuentes, a graduate student at Lamont, and I presented new work on the estimation of Soviet yields at the Eastern Kazakhstan test site from 1978 through 1982 using digital recordings of seismic surface waves. Our work, published in 1984, was prompted by a letter I received on December 15, 1982, from Peter Marshall, who had long worked on seismic verification in Britain, about my use of surface waves for yield determination in our 1982 Scientific American paper. Marshall wrote, “I have always thought that [the surface wave magnitude] Ms should be a stable indicator of yield. Some LR [long-period Rayleigh wave] trains from the RTS [Russian Test Site in Eastern Kazakhstan] have shaken my confidence in that there are examples of where the average Ms has been significantly reduced in amplitude in all azimuths [directions].”
What concerned Marshall and others, understandably, was that some explosions at that site triggered the release of large amounts of natural stress in the surrounding rocks. The tectonic release at the time of explosions in hard rock, depending on the amounts of natural compressive stress built up before hand, reduces the size of the surface waves from shots in Eastern Kazakhstan. Because those surface waves are reduced in amplitude, the yields computed from them from Ms are too small. Tectonic stresses in Nevada, however, are extensional, not compressive, and have the opposite effect on the size of surface waves.
Cifuentes and I dealt with tectonic release in a study of twenty underground explosions at Eastern Kazakhstan. We used the ratio of the amplitudes of two surface waves—Love waves/Raleigh waves—as a measure of the amount of tectonic release that was contaminating Raleigh waves produced by the explosions themselves. Love waves are generated only by natural tectonic stress release, not the explosion itself. We calibrated a new mb-yield relationship for Eastern Kazakhstan by calculating yields from surface waves, but only for those explosions that were characterized by a small-to-negligible component of tectonic stress. We then used that relationship to determine yields from mb for all twenty explosions.
We concluded, “The yields of the seven largest Soviet explosions are nearly identical and are close to 150 kilotons, the limit set by the Threshold Treaty.” For explosions characterized by a large Love to Raleigh wave ratio—that is, a large tectonic component—we recommended using just our new mb-yield relationship to determine their yields from body waves (mb) alone. This is what I had hoped and expected that AFTAC would do in 1977, but they did not.
Our position was slowly becoming clear to journalists. John Wilke wrote about the AGU symposium in the Washington Post on June 3, 1983. He mentioned a classified study at the Livermore Lab, stating that a Livermore physicist said publicly to him, “Whatever it is believed in Washington, it is now clear that officials here at Livermore Lab do not believe that the Soviets have violated the 150-kiloton limit.”
Journalist R. Jeffrey Smith, who also covered the symposium, quoted seismologist Bernard Minster of UC San Diego in the June 17, 1983, issue of Science: “Based on what I heard this morning, I think we have a hard time justifying statements that the Soviets are cheating.” Robert North, another consultant to the Defense Department, said, “After listening to the presentations…most people would agree that you cannot assert that the Soviets have violated the Treaty.” Smith went on to state, “Milo Nordyke, who directs the verification program at Lawrence Livermore National Laboratory, where the bulk of the government’s analysis is conducted, said after the AGU meeting ‘DARPA, which takes the most conservative view, certainly seems to be in the minority. Of course, with the conservative view, you automatically get some evidence of Soviet violations. But you have to use the best estimate, not the most conservative one. This is a message that the politicians in Washington have a hard time understanding.’” Pike and Rich of the Federation of American Scientists also quoted Nordyke as saying “there is no hard evidence of Soviet test violations.”
DARPA and AFTAC supported several analyses of the attenuation of short-period P waves beneath test sites in Eastern Kazakhstan, Nevada, Mississippi, Amchitka Island in the Aleutians, and Algeria. In January 1984 Robert Blandford and colleagues at the consulting firm Teledyne Geotech computed corrections to mb magnitude for each site with respect to Nevada. They reported that an mb of 6.17 was associated with 150-kiloton explosions at Eastern Kazakhstan, very similar to the results we presented in 1983. They found that P waves from French explosions at the Algerian hot spot were attenuated by about the same amount as those in Nevada and the attenuation of P waves beneath Amchitka was similar to those beneath Eastern Kazakhstan.
DARPA PANEL MEETINGS ON YIELD DETERMINATION
In January 1983, I was invited to be a member of a Department of Defense Technical Review Panel on Threshold Test Ban Treaty Verification Issues that was convened by DARPA. After attending its first meeting, I informed DARPA that I would be out of the country and not able to attend the next meeting set for about July 29. I stated, “I have had a fairly long telephone conversation with Gene Herrin, and will send him written comments in response to his unclassified letter. I also think that it is important that my views be represented along with those of Sean Solomon [of MIT]. I understood that Sean also will not be able to attend.”
On August 17, 1983, Alewine, who had become director of the Geophysical Sciences Division of DARPA, sent me a letter informing me that a separate classified package of the completed panel report had been mailed to me. His unclassified letter states, “As we discussed in the Panel meetings, the methodology for the use of surface waves in yield estimation has not received the level of critical review as has that for body waves.” He wrote, “We would like to convene the Panel about mid-October to examine fully the status of using surface waves for TTBT monitoring…we would like for the Panel to begin review of technical aspects of Comprehensive Test Ban Issues at the October Panel meeting.”
I wrote an unclassified letter to Herrin on September 16, 1983, with my general views about the Panel Report and a classified letter to DARPA about some specific points. I stated, “I conclude that the panel’s recommended value for the bias [in magnitude between the Nevada and Eastern Kazakhstan] is still too low. A consequence of this, of course, is that calculated yields will still be too high.” On May 31, 1983, Under Secretary of Defense Richard D. DeLaure wrote to Frank Press, then the president of the National Academy of Sciences, stating that he foresaw no need for a parallel review effort on questions of verifying nuclear test bans to be conducted by DARPA and that all legitimate questions of objectivity and credibility were well met by the [present] DARPA panel.”
I also stated in my letter, “I am seriously concerned about the procedures that have been followed in previous panels of which I was a member. Let me be specific on three points. DARPA officials, Bache, Alewine, were present at all of the sessions of the panel at its January 1983 meeting. They have consistently and often reiterated their views that the bias between those two test sites is small. They have actively and aggressively participated in the deliberations of the panel as if they were members. Under those circumstances, I believe that it is difficult for different views to be heard and to be considered in a thoughtful manner.
“Secondly, the panel has adopted positions that are at odds with those of several distinguished scientists including Dr. Peter Marshall, of the United Kingdom, Springer, Rodean and [Peter] Moulthrop of Livermore, Evernden, etc. I believe that none of them has had a chance to respond to criticisms of their work made in either the latest or earlier reports of the panel. Thirdly,…my sense is that the panel has had too little time during its meetings to write a thoughtful and independent report of its own.”
I sent copies of my letter to Alewine and the panel members. I was not invited to the October 1983 meeting. I asked panel member Tom Jordan of the University of Southern California if I was still on the panel, and he said no. I never received a letter from DARPA to that effect. I was not invited to be a member of future DARPA or AFTAC panel meetings.
The DARPA panel continued to meet until at least 1985, because I received an unclassified draft summary of their work dated February 1985. It discussed the contamination of surface waves from tests in Eastern Kazakhstan and recommended not using them for yield determination. They did not acknowledge the significant problems of using just P waves for yield determination. I was told that members of the panel disagreed about magnitude bias and wanted sections put in about it, but that material was removed from the final report.
Writing in the New York Times on April 2, 1986, Michael Gordon, the military affairs correspondent, stated, “The Central Intelligence Agency has changed its procedures for estimating the yields of large Soviet nuclear tests because it has decided its previous estimates were too high, Reagan Administration officials said today…. Experts familiar with the change said it would lower estimates of the yield of Soviet tests by about 20 percent.”
Gordon went on to say, “On Oct. 18, a panel of scientists selected by the Defense Advanced Research Projects Agency prepared a classified report that concluded the Government’s method for estimating the yield of Soviet explosions was based on faulty assumptions. The panel’s report was submitted in late October to the Joint Atomic Energy Intelligence Committee, which issues reports on the size of foreign nuclear explosions. The committee is made up of members from the military services and intelligence agencies…. On Dec. 17, the Joint Atomic Energy Intelligence Committee recommended that the C.I.A. adopt the advice in the report commissioned by the research agency. Officials said the Defense Intelligence Agency disagreed, but was overruled.
“Officials said applying the new method retroactively would still leave about a dozen Soviet tests that appear to be above the limit, and one official said only three or four of these exceeded the limit enough to warrant special concern.” These statements imply that the bias in magnitudes for Eastern Kazakhstan was about 0.2, not 0.3 to 0.4 as several of us had recommended. I had assumed, apparently incorrectly, that the U.S. government had corrected the formula for estimating Soviet yields in 1977. Gordon’s article indicated that it did not occur until 1986. U.S. formulas for estimating Soviet yields have changed with time and are still classified.
Gordon also stated, “Richard N. Perle, the Assistant Secretary of Defense for International Security Policy, reportedly opposed adopting the recommendations and argued that the issue needed more study. Mr. Perle declined to discuss the issue. Administration experts, who asked not to be identified, were divided about whether the change should lead the Administration to drop its allegations against the Soviet Union.”
PERLE AND THE SCIENTISTS
Brian McTigue produced a television interview in 1986 for San Francisco station KRON called “Richard Perle and the Scientists: The Controversy Over Nuclear Testing.” They filmed it during the debate about alleged Soviet cheating on the Threshold Treaty. It focused on comments made by seismologists Charles Archambeau of the University of Colorado, James Hannon of Livermore, and me, countering statements by Perle. Perle served in the Reagan administration from 1981 to 1987 as assistant secretary of defense for international security policy and later as chairman of the Defense Policy Board, an influential group of advisers to the Pentagon. The program can be viewed on youtube.com.
I single out Perle here because he was a hard-liner and the strongest opponent of the control of nuclear weapons for more than fifty years. He exaggerated Soviet nuclear capabilities on many occasions. What is particularly relevant here is that he knew nothing about seismology, which was at the very heart of estimating Soviet nuclear yields and possible cheating. Congressional, arms control, and scientific communities knew him as the “Prince of Darkness.”
Here are excerpts from the 1986 interview.
INTRODUCTION: The Soviet Union has stopped testing and is abiding by a nuclear test ban, but the United States has continued to test weapons underground claiming the Soviets have cheated. The Administration says the Soviets tested weapons more powerful than agreed to in 1974, but have they?
Rollin Post and our Target 4 Investigative Unit found the Administration is ignoring evidence that the Soviets never cheated, that they are following the treaty.
CHARLES ARCHAMBEAU [SEISMOLOGIST, COLORADO]: If the scientific data doesn’t quite agree with your political position, what is done is to bend the data a little bit.
PERLE: Baloney! It is not a question of scientific evidence. It is a question of scientists playing politics. I’ve looked carefully at the evidence and have concluded as President Reagan did that there is significant evidence that the Soviets have violated the 150-kiloton threshold.
ROLLIN POST [INTERVIEWER]: This has been the position of the Administration since 1983. But it has also caused a rebellion among the very scientists the Defense Department relies on to estimate the size of the Soviet tests. Target 4 interviewed some of those seismologists and they all said the Soviet Union has not violated the 1974 Test Ban Treaty.
ARCHAMBEAU: At present there is no evidence that the Soviets have tested over 150 kilotons, none whatsoever.
LYNN SYKES [SEISMOLOGIST, NEW YORK]: The treaty itself states that neither country should test above 150 kilotons and I have no evidence that indicates to me that the Soviets have done that.
WILLARD HANNON [SEISMOLOGIST, LIVERMORE NATIONAL LABORATORY]: I don’t believe that the evidence supports a militarily significant violation.
PERLE: The best experts available spent years studying this and came to the conclusion that it was likely the Soviets had violated the 150-kiloton threshold.
Well, with all due respect he [Archambeau] is wrong, there is lots of evidence. He may not be persuaded on the basis of the evidence, but to say that there is no evidence is just flatly wrong.
POST: Lynn Sykes of Columbia says that the Soviet Union has not violated the 150-kiloton limit of the threshold treaty as alleged. He’s wrong?
PERLE: He’s entitled to his opinion. He’s a professor sitting up at Columbia.
Well, all that seismology enables you is to make an estimate as to the yield of an event. Even by that standard alone, there is evidence that suggests the Soviets have violated it, your experts not withstanding. There is other evidence as well that is sensitive and of a classified nature.
POST: Mr. Perle would only say the other evidence involved satellite and electronic surveillance. Target 4’s investigation learned that Mr. Perle had already convened a panel of experts, which looked at this other evidence and rejected it.
PERLE: They came to the conclusion that of the many ways of estimating yield, seismology was the single most important and I happen to agree with that.
I did not particularly care much what their answer was, it did not have any profound bearing on our policy.
POST: Target 4’s investigation has also uncovered evidence that Mr. Perle improperly tried to manipulate intelligence agencies in a biased direction. Example: Perle’s letter to the Air Force when its intelligence unit asks seismologists to advise on Soviet nuclear tests. According to sources who have seen the letter, it said the intelligence community is undermining the Administration’s position. My Department will control this area. I asked Perle about the letter.
PERLE: I don’t remember the exact words of the letter, but my concern was the concern that I have been expressing to you throughout this interview, which is that we have tended, I think wrongly, to exclude the non-seismic evidence that bears on the estimation of the yield of Soviet tests.
They’re all seismologists; they’re a bunch of seismologists feathering their own nests. Well, seismologists have dominated this field from the beginning. It’s how they make their living. The day that it is concluded that we can get along without attributing the importance to seismology that we do—some of these fellows are going to be looking for jobs.
ARCHAMBEAU: The scientific opinion is close I’d say to unanimous. Right now Mr. Perle finds it extremely difficult to find any scientists that will defend the DoD Perle position and that’s because there just aren’t any that believe it.
SYKES: I think that one view that is often put forth is that arms control agreements are not in the best interest of the United States. That the Soviets will cheat and then attempt to have a self-fulfilling prophecy by coming up with some procedure, an incorrect one, that indicates to them that the Soviets have cheated.
In one of Perle’s statements, he commented that he had additional classified information that led him to different conclusions about verifying Soviet nuclear testing. His responses to similar previous statements had led people with high-level clearances for all of the relevant documents to reexamine them. Perle was found wanting.
In a later frightening interview on the Public Broadcasting Service’s program Frontline, Perle made the case for using a war with Iraq to remake the Middle East. He stressed the significance of the World Trade Center disaster of September 11, 2001, in shaping the Bush administration’s thinking about the links between terrorism and weapons of mass destruction.
SENATE AND HOUSE ACTIONS ON NUCLEAR TESTING
The U.S. House of Representatives and the Senate, which were controlled by Democrats, held hearings on Soviet compliance with the Threshold Treaty and verification of a full test ban in 1985 and 1986. I gave oral and written testimony on both topics, twice to House subcommittees and once to the Senate Foreign Relations Committee.
Alewine sent a letter on December 16, 1985, to Representative Beverly Byron of the House Committee on Armed Services criticizing several statements in my testimony before her subcommittee on November 20, 1985. Alewine said, “Dr. Sykes represents one extreme in the assumptions he advocates (leading to lower yield estimates than most). There are others, just as responsible and knowledgeable, who advocate extreme assumptions on the opposite end (leading to higher yield estimates). The reviews conducted by the DoD have tended to balance these extremes.” He made no mention of the several scientists and officials at Livermore and Britain who disagreed with his views. Alewine also stated, “The flippant remarks of Dr. Sykes concerning the possibilities for cavity decoupling evasion gloss over a very difficult and threatening problem that must be addressed.”
In the 1980s I debated Alewine several times about Soviet yields and the verifiability of a full test ban treaty. I had no doubt that Alewine, Bache, Perle, and others consistently played “hard ball.” Someone said that if you want to argue with those people, you have to be willing to jump into the pigpen. The debate went on for a very long time, and I am glad I kept at it. My testimony in 1985 and 1986 likely contributed to Congress’s taking an active role in the verification of a full test ban and ascertaining if the Soviet Union had cheated on the Threshold Treaty.
INDEPENDENT REVIEW BY THE OFFICE OF TECHNOLOGY ASSESSMENT
The Senate Select Committee on Intelligence, the House Committee on Foreign Affairs, and the House Permanent Select Committee on Intelligence requested that Congress’s Office of Technology Assessment (OTA) undertake an assessment of these test ban issues in 1986. OTA had previously performed studies for Congress on arms control and other scientific and technical issues.
OTA conducted the first major independent review on seismic verification of nuclear testing from 1986 to 1988. For the first time, the departments of Defense and Energy were not the sole sources of information in the government.
OTA formed an advisory panel of nineteen individuals from various government agencies, universities, the weapons labs, and consulting firms. Paul Richards of Lamont, who had been involved in test ban issues for some time, and I were members. Gregory Van der Vink of OTA was the project director. He received a PhD in geophysics from Princeton and became interested in science policy, especially arms control, through Frank von Hippel and his group at Princeton. Frank had long worked on national security issues and energy. Greg persuaded OTA to conduct the test ban study.
The study itself and its 1988 publication Seismic Verification of Nuclear Testing Treaties were approved by the Technology Assessment Board of Congress, which consisted of twelve members chosen equally from Republicans and Democrats and from the House and Senate.
The 1988 report stated, “Seismic monitoring is central to considerations of verification, test ban treaties, and national security.” It addressed two key questions:
1. Down to what size explosion could underground testing be monitored seismically with high confidence?
2. How accurately could the yields of underground explosions be measured seismically?
The answers to these questions would provide the technical information that lay at the heart of the political debate over:
1. how low a threshold test ban treaty with the Soviet Union we could verify;
2. whether the 1976 Threshold Test Ban Treaty was verifiable; and
3. whether the Soviet Union had complied with present testing restrictions.
OTA held workshops of two days each on (1) Seismic Network Capabilities, (2) Identification, (3) Evasion, and (4) Yield Determination. About a dozen individuals participated on each panel. Richards and I were on the panels on Identification and Yield Determination; Richards was also on Network Capabilities, and I was also on Evasion. While some of the briefings were at the secret level, the 1988 report was cleared by relevant government agencies prior to its open publication. The report is a good primer on seismology as it relates to nuclear monitoring and on the role of verification in the context of national security.
In its executive summary, the report concluded that unless differences in the transmission of seismic P waves beneath Eastern Kazakhstan and Nevada were taken into account, the sizes of Soviet explosions were greatly overestimated. Once these differences were appropriately considered, the report stated, “All of the estimates of Soviet and U.S. tests [since the TTBT became effective in 1976] are within the 90 percent confidence level that one would expect if the yields were 150 kt or less. Extensive statistical studies have examined the distribution of estimated yields of explosions at Soviet test sites. These studies have concluded that the Soviets are observing a yield limit consistent with compliance with the 150 kt limit of the Threshold Test Ban Treaty [original boldface].” I consider this an important victory for good science, sound science policy, and arms control in general.
The 1988 report has a table on page 124 showing my calculations of the yields of the six largest explosions at Eastern Kazakhstan since 1976. All of those yields were close to the 150-kiloton limit and well within the uncertainty expected for its observance.
ON-SITE MEASUREMENTS OF YIELD
Two non-seismic methods are available for determining the yield of explosions near the 150-kiloton limit of the Threshold Treaty. One involves drilling back into the explosion point and obtaining samples of various radioactive materials produced by the explosion. This method, often called radiochemical, or rad-chem, has an uncertainty of about 10 percent. Although the United States often used rad-chem for its tests, applying them to explosions on-site could reveal information about the characteristics of weapons that the Soviets and Americans likely wanted to keep secret.
Another method for yield determination, abbreviated CORRTEX, involves drilling a second hole very close to and equal in depth to that used for a large underground explosion. When the nuclear explosion occurs, a cable in the second hole is crushed. This method measures the speed of the shock wave, which travels faster than the speed of sound, close to a nuclear explosion as it crushes the cable. The satellite hole must be within about 33 feet (10 meters) of the hole containing an explosion with a yield of about 150 kilotons.
These measurements permit yield to be determined with an uncertainty of about 30 percent. This method, of course, is very intrusive because it is so close to the explosion. Its advantage is that it does not reveal the radiochemical contents of the materials produced by the explosion. It is not applicable, however, to small nuclear explosions. The 1988 report contains an extensive appendix on this method. An idea was for the United States to use CORRTEX to monitor a Soviet test and for them to use similar equipment for a U.S. test in Nevada.
By 1986 General Secretary Gorbachev of the Soviet Union had put President Reagan under pressure to push for a full test ban. Reagan proposed that if Gorbachev would agree to work on the verification of the TTBT and PNET first, the United States would then negotiate ways to implement a step-by-step program limiting and ultimately ending nuclear testing. Reagan said, however, that he would not ratify the TTBT even if the Senate gave its advice and consent.
During expert talks in July 1987, the Soviets proposed calibration of test sites to reduce uncertainty in yield estimation. They invited the United States to measure yields at one of their main sites using CORRTEX and regional seismic observations. The two countries then signed a bilateral agreement to conduct Joint Verification Experiments (JVEs) in 1988 at Eastern Kazakhstan and Nevada. Each country was to detonate one explosion with a yield between 115 and 150 kilotons.
The United States did not release the yield of the Soviet JVE test of September 14, 1988, which it monitored using CORRTEX. Each country released to the other the yields of the JVE and five previous tests at each site. The 1988 agreement stated that yields were not to be released to additional people or countries without the consent of the other. As far as I know, these yields were kept secret, and still are. Nevertheless, a detailed report on the two Joint Verification Experiments in the New York Times by Michael Gordon states that American and Soviet on-site measurements were said to give yields of 115 and 122 kilotons, respectively, for the Soviet JVE, an average of 118.5 kt.
In 1989 Göran Ekström, a geophysicist then at Harvard, and I published an average magnitude, mb, of 6.115 with a very small uncertainty of +/- 0.018 for the Soviet JVE using reports of P waves from sixty-eight seismic stations. We then used three mb-yield relationships derived from various test sites where yields were available. Each was corrected for mb bias with respect to Eastern Kazakhstan. We chose a bias of 0.35 for explosions in hard rock and those below the water table in Nevada. The three calibrations gave yields very similar to those reported in the New York Times for the Soviet JVE. We extrapolated the yield of 118.5 kilotons measured on-site for the Soviet JVE to 150 kilotons. It gave a magnitude mb of 6.20, very similar to the magnitudes of the six largest explosions at that test site published in the 1988 OTA report.
YIELDS OF SOVIET NUCLEAR TESTS MEASURED USING LG SEISMIC WAVES
A third method of determining yields from seismic waves came of age in 1992. In 1973 Otto Nuttli of St. Louis University started to develop a magnitude scale called mbLg that uses short-period seismic waves called Lg with periods near one second (one cycle per second frequency). In 1952 Press and Ewing of Lamont had described and named Lg and another slow surface wave called Rg, which propagate in continental areas. Lg is often the largest wave on a short-period seismic record from earthquakes to stations at regional distances within continents. P waves from explosions, however, are relatively large compared to Lg, making Lg a good method for identifying underground explosions and potentially for determining their yield.
Nuttli developed mbLg magnitudes suitable for all parts of the United States. In regions of older crust, Lg is observed at distances of more than 3000 miles (5000 km). Examples of this are Lg recordings at Palisades, New York, of waves that cross the ancient rocks of Canada from earthquakes in the Yukon and northern Alaska.
Lg radiates symmetrically from explosions and earthquakes, and it does not have the major difficulty of P waves, which need a correction for differences in wave propagation through the uppermost mantle of the Earth. Hence, it became very useful for yield determinations.
In 1992 Frode Ringdal of Norway, Marshall of Britain, and Alewine of DARPA obtained more precise estimates of mbLg than Nuttli had for explosions in Eastern Kazakhstan using data from the NORSAR (Norway) and Grafenberg (Germany) seismic arrays. Instead of measuring the amplitude of a single wiggle of Lg, they obtained an average over several minutes. Lg, as shown in figure 10.3, is not a single pulse but a train of seismic waves that builds up and then decays slowly. Its records are more like those of waves that travel great distances in the oceans, called the T phase, and those made on the moon.
FIGURE 10.3
Upper seismogram is from an event at a regional seismic station that propagated along a continental path. Lg is its largest signal. Lower seismogram is from an event to a station at a large distance (a teleseismic signal). The P wave is its largest signal, and Lg is very small.
Source: Office of Technology Assessment, 1988.
Ringdal and colleagues analyzed seismic data for 101 nuclear explosions at the Shagan River portion of the Eastern Kazakhstan test site, which was the site of most large underground tests. Their measurements of mbLg and mb determined from P waves differed systematically by as much as 0.15 magnitude units between two subareas of the Shagan River site. They discovered that mb values for four explosions with yields published in 1989 by V. S. Bocharov and his Russian colleagues also varied in the same way with respect to values of mbLg. Those subareas are separated by a series of major faults oriented northwesterly. Hence, Ringdal and his colleagues concluded that mbLg is a more reliable measure of yield than either mb or surface waves.
They found a magnitude mb bias with respect to Nevada of 0.45 for the southwestern part of that area and 0.30 for the northeastern part. These are close to the biases of 0.3 to 0.4 that several of us determined earlier, and clearly not zero. By subdividing that test site into two parts, Ringdal and colleagues provided better determinations of yields than any of us had obtained previously. They obtained an average yield for the Soviet JVE explosion of 1988 in the southwest part of the test site of 108 kilotons, which compares very well with the 118.5 kilotons reported in the New York Times for the two close-in CORRTEX measurements.
A lingering question is whether the Soviet Union has cheated on the Threshold Treaty by conducting any tests above its 150-kiloton limit since its start date in 1976. It is important to understand that all yield determinations have uncertainties associated with them. For explosions of 150 kilotons, some estimates will be somewhat larger, others somewhat smaller, and some right on, as shown for the three following explosions with yields near 150 kilotons.
Only one of the explosions studied by Ekström and Richards, that on April 3, 1987, for which they calculated a yield of 176 kilotons, exceeded the 150-kiloton threshold. Ringdal and colleagues, however, obtained 140 kilotons for that explosion using mb and mbLg. For a second explosion, on August 4, 1979, the two sets of authors obtained 153 and 132 kilotons. For a third event, on October 27, 1984, they calculated 165, 104, and 140 kilotons. Those measurements taken together indicate that the three largest explosions at Eastern Kazakhstan testing area since 1976 were at or close to the 150-kiloton limit within the uncertainties of the measurements.
When asked by a member of a subcommittee of the U.S. House of Representatives in 1985, I stated that the yields of Soviet tests in Eastern Kazakhstan near the threshold of the treaty could be determined [then] with an uncertainty of about 30 percent. Donald Kerr, the director of Los Alamos, said my estimate of the uncertainty in yield of 30 percent was small compared to extrapolations that could be made up to a factor of about two times. With the introduction of Lg measurements, the uncertainty in yield estimation for Eastern Kazakhstan was reduced further to about 25 percent.
To appreciate what these numbers mean in terms of accuracy, a person driving 25 percent faster than a 55 mile per hour speed limit would be traveling at 69 miles per hour and might or might not receive a speeding ticket. If the person were traveling 25 percent slower, the speed would be 44 miles per hour, and he or she certainly would not get a ticket. If Russia had decided to test weapons at yields 25 percent higher than the 150-kiloton limit, or 187 kilotons, the yield determined by the United States likely would be between 150 and 234 kilotons but more likely close to 187 kilotons. The analogy is that they probably would be “given a speeding ticket”—that is, accused of cheating on the TTBT. More than one test at 187 kilotons would have substantially increased the chances of the United States’ determining that the Soviet Union was testing above the threshold of the TTBT.
Alewine joined Ringdal and Marshall as third author of their 1992 paper. This probably was an unstated acknowledgment by Alewine, as well as by the U.S. Defense Department, that the determination of yields at that test site had been resolved. It was clear that earlier U.S. charges of Soviet cheating, spearheaded by Alewine, Bache, Perle, and Romney, were false. The Soviets, in fact, had been in compliance with the 150-kiloton limit of the Threshold Test Ban Treaty. With that, the “yield wars” were finally over. Alewine told me in 2009, at a meeting in Vienna on nuclear test testing, “I guess you got about 50 percent of things right and we [DARPA] 50 percent.” I would give them no more than a 5 percent.
In 1989 Bocharov, Zelentsov, and Mikhailov of the Soviet Union published an official list of ninety-six underground nuclear explosions at the Eastern Kazakhstan test site through 1972, before the Threshold Treaty became effective. Mikhailov became minister of atomic energy of the Russian Republic in 1992. While most yields are listed within a broad range, several are given exactly. They list two larger than 125 kilotons: 165 kilotons on November 2, 1972, and 140 kilotons on December 10, 1972. My determinations of those yields were 154 and 138 kilotons; Ringdal and colleagues calculated 169 and 158 kilotons. I estimated the yield of the largest underground explosion at that test site, on July 23, 1973, as 193 kilotons. All three of those explosions, of course, occurred before the Threshold Treaty became effective in 1976.
From 1990 to 1992, physicist David Hafemeister worked for the Senate Foreign Relations Committee to examine arms control treaties at the end of the Cold War. In an article published in 2005, he stated, “This charge [of a probable violation of the Threshold Test Ban Treaty] was removed in 1990 after the 1988 CORRTEX measurements at Semipalitinsk [Eastern Kazakhstan] Test Site and after properly taking into account the geological differences between test sites…. The U.S. record on TTBT noncompliance charges was not entirely honorable.”
By 1990 the United States and Russia completed a considerably revised protocol for the Threshold Test Ban Treaty. I doubt if more than a few people ever read the new protocol, which is exceedingly long. It called for CORRTEX-type measurements for U.S. and Russian weapons tests larger than 50 kilotons. Because the Russians stopped testing before the treaty entered into force in late 1990, the United States has not been able to make additional CORRTEX measurements of Russian nuclear explosions. Under the ratified TTBT, the Russians, however, were able to monitor two U.S. explosions in Nevada before President Clinton halted U.S. testing in 1992. The TTBT and its companion Peaceful Nuclear Explosions Treaty (PNET) are still in force.
A SOVIET ASSESSMENT OF THE THRESHOLD TEST BAN TREATY
Roland Timerbaev of the Russian Ministry of Foreign Affairs, who attended the negotiations for the Threshold Treaty in 1974, wrote in 2006 about the history of the treaty. In a long footnote, he states that the yield of the U.S. Joint Verification Experiment (JVE) of 1988 in Nevada was 180 kilotons and significantly exceeded the 150-kiloton limit of the treaty. He quotes an interview on December 7, 2005, in which V. N. Mikhailov of the Russian Ministry of Atomic Energy stated that a collapse depression was formed by that JVE. Timerbaev states, “I might add that the Americans were very upset about this and requested that we not speak about the matter publicly; however, the story has since become public knowledge through the media.” Springer and others list the yield of the U.S. JVE, called Kearsarge, as 100–150 kilotons and do not mention a collapse feature.
Timerbaev also gives information about how the yield threshold for the TTBT was debated in 1974, which I did not know. He states that the Soviet Ministry of Defense and the agency responsible for building and testing Soviet weapons (called at the time the Ministry of Medium Machine Building or Minsredmash) pushed to allow the USSR to undertake one or two tests [presumably per year] with yields over a megaton and three to four of 500 kilotons.
Timerbaev states that it seemed to him during the [1974] negotiations that the threshold would be set in the range of a few hundred kilotons. He quotes a conversation in 1984 with a former American official reporting that in 1974 the U.S. military wanted to establish a threshold at 600 kilotons but Henry Kissinger, Nixon’s secretary of state, sharply objected. Kissinger and Gromyko agreed upon a 200-kiloton threshold, but Nixon, at Kissinger’s behest at the last minute, wanted a 150-kiloton limit. That number was agreed upon in the last few days of the negotiations in Moscow just before Nixon and Brezhnev completed and signed the treaty in early July 1974.
