ra public interest report journal of the federation of american scientists (fas) volume 50, number 6...

RA.S ● PUBLIC INTEREST REPORT

Journal of the Federation of American Scientists (FAS)

Volume 50, Number 6 November/December 1997

Anatomy of a False Alarm: Silence Follows Hyped Leaks

Government leaks of alarming, semi-digestedand inaccurate intelligence information haveoccurred regularly over the last half-century.Somehow the subsequent report of a false alarmnever gets the same press attention.

This process has survived the Cold War, andnow threatens to disrupt the peace buildingprocess, as shown by this hrilIiant review of theRussian nuclear-test-that-never-was by the distin-guished geologist Lynn R. Sykes of ColumbiaUniversity. Because very small earthquakes cannow be picked up by seismic arrays designed tomonitor the negotiated but unratified Comprehen-

sive Test Ban Treaty, small earthquakes nearnuclear test sites will sometimes be mis-identifiedas tests. And because weapons laboratory activityat the test site cau arise from (unprohibited)subcritical tests, it is only too easy in cases ofcoincidence to put 2 and 2 together to getsomething that is not foursquare. Hopefully thisincident will help, rather than hurt, the upcomingratification of the nuclear test ban by revealinghow sensitive are the instruments of its verifica-tion, and by inoculating the body politic againstfuture misapprehensions.

Small Earthquake Near Russian Test Site Leads to U.S. Charges of Cheatingon Comprehensive Nuclear Test Ban Treaty -

By Lynn R. Sykes

On August 28 the Washington Times carried alead story “Russia suspected of nuclear testing.” Itwas followed up the next day by the Washington Postand the New York Times, the latter with the headline“U.S. Suspects Russia set off Nuclear Test.” In thebody of those and other press reports, however, thenature of event on August 16--whether it was anuclear explosion or an earthquake at or near theRussian Arctic nuclear test site at Novaya Zemlya--was expressed as being still in doubt. Nevertheless,remarks quoted in the press like “this one certainlyhad characteristics that at least would lead some tobelieve that there had been an explosion that causedthe event” emphasized the likelihood of a clandestinenuclear explosion. Officials in Moscow were quotedas strongly denying having tested a nuclear weapon.They maintained that the event was a small earth-quake in the Arctic Ocean to the east of Novaya

Zemlya.This is the first allegation by U.S. officials of

cheating by Russia (or of any other country) since theComprehensive Test Ban Treaty (CTBT) was adoptedoverwhelmingly by the UN General Assembly morethan a year ago. Soon thereafter, the treaty was signedby all of the acknowledged nuclear weapon states--China, France, Great Britain, Russia, and the UnitedStates. It now has been signed by 146 countries, Thewidely publicized allegation comes at a very sensitive

Lynn R. Sykes is Higgins Professor of Earthand Environmental Sciences at the Lamont-Doherty Earth Obsematory of ColumbiaUniversi@ Pahsades NY 10964. He has workedon and written about verification of nucleartesting for more than 30 years.

November~ecember 1997

moment as President Clinton stated at the UN onSeptember 22 that his administration would submitthe CTBT to the Senate. Passage by the Senate isproblematic since a 2/3 positive vote is need for U.S.ratification of the Treaty. The accusation of Russiancheating may well be the beginning of an acrimoniousdebate over the CTBT. The August event is likely toplay a key role in debate about the verifiability of theTreaty.

The story in the Washington Times appeared 12days &er the event of August 16 ad just as the LaborDay holidays were commencing. Since then, how-ever, a strong consensus has developed among expertsin the seismological communities in the U. S., theU. K., Norway and Canada who are concerned withnuclem verification that the event of the 16th was, infact, a small earthquake. It was located in the KaraSea section of the Arctic Ocean to the east of the twomain islands of Novaya Zemlya and more than 100km to the southeast of the Russian test site itself.Recent analyses of its seismic waves indicate that theevent had the characteristics of an earthquake, notthose of au explosion. This was evident once theywere compared carefully against seismic records fromknown Russian nuclear explosions at the NovayaZemlya test site that were conducted before Russiadeclined a moratoria on nuclear testing in 1990 andwith those of an nearby earthquake in 1986. Never-theless, more than a month after the latest eventseveral top U.S. policy makers either were not awareof this scientific consensus or maintained that thenature of the event remained ambiguous.

This is the 4th of 5 small earthquakes near NovayaZemlya since 1986 that has been cited by the U.S.Defense Department (DoD) as being of either suspi-

cious or problematic origin in terms of nuclear verifi-cation. In each of those cases, intense special studiesrevealed that each was a small earthquake. Thoseconclusions, not being as sensational as the accusa-tions, were neither carried by the press nor in the pressreports on the 1997 event.

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This article summarizes the scientific evidencebearing upon the nature of the 1997 event, attempts todecipher who in the U.S. Government knew what andwhen about the event, and analyzes how key Govern-ment agencies may have arrived at the erroneousconclusion that the Russians either did or may havecheated. It urges more careful U.S. analysis beforeaccusations are prematurely leaked to the press andrecommends several confidence building measuresthat would provide yet greater assurance of compli-ance (or lack thereo~ with the Test Barr Treaty.

A few key people within the government wereresponsible for leaking misleading and outdatedinformation to the press about the event. Data pro-vided by the International Monitoring System for theCTBT as well as those horn other unclassified seismicstations in several countries that are not formally apti of treaty monitoring provided enough informationto make a clear judgment that the small event ofAugust 16 was, in fact, an earthquake and not aclandestine nuclear explosion. The successful identi-fication of five small events on and near NovayaZemlya as earthqu~es demonstrates the effectivenessof verification technologies. This conclusion stillneeds to be conveyed to U.S. policy makers, many ofwhom lack the resources to arrive at or obtain inde-pendent judgments about scientific and technical datarelated to verification of the CTBT. Once allegationsof clandestine nuclear testing were passed up govern-mental chains of command, it became difficult laterfor high officials to state that the allegations werefalse.

International Monitoring Systemfor the Test Ban Treaty

The International Monitoring System (IMS), theInternational Data Center (IDC) and the U. S. Na-tional Data Center played key roles in recording andmdyzing data from the August 16 event. The presentstatus of each is described as background before theevent itself is discussed.

Verification was a major item of debate during thenegotiations for the nuclear test ban treaty in Genevain 1995 and 1996. The 1963 Limited Test Ban Treaty(LTBT) put an end to nuclear tests in the atmosphere,space and underwater by each of the signatories but itdid not prohibit underground testing. France andChina, who dld not sign the LTBT, did test in the

atmosphere after 1963 but each eventually decided toconduct their nuclear tests solely underground as well.The CTBT prohibits nuclear explosions of any size,i.e. any nuclear yield, in all environments. The UnitedStates wisely insisted in the negotiations that severalnetworks of sensors be installed around the world toensure that a clandestine nuclear explosion in anyenvironment would be detected and identified quickly.The treaty adopted by the UN incorporates U.S.proposals for global networks with four types ofsensors: seismological, underwater sound (hydro-acoustic), infrasound, and radlonuclide.

The CTBT Treaty and its verification protocol setup and specify an International Monitoring System,communication networks, an International DataCenter, confidence-building measures, institutionalarrangements for consultation and clarification, andprocedures for requesting and carrying out on-siteinspections of events thought by one or more partiesto be either clandestine nuclear explosions or eventsof ambiguous origin.

The seismological portion of the IMS grew out ofthree experiments in data exchange arranged by theGroup of Scientific Experts (GSE) of the UN’sCommittee on Disarmament. The final techical testof the IMS known as GSETT3 (Group of ScientificExperts Technical Test 3) has been in continousoperation since January 1, 1995. Once the CTBTenters into force the seismic portion of tie IMS isspecified to consist of 50 primary stations distributedglobally (Figure 1) and 120 auxiliary stations (Figure2). There are 40 primary and 81 auxiliary stationsnow operating; 2 addltiond prim~ and 8 auxiliarystations me scheduled to be operational by the end of1997. Most of the primary stations consist of arrays

‘igure 1 Prima~ seismic statiom of the International4onitoring System for the Comprehensive Test Ban Trea@.

November/December 1997

of seismometers designed to increase the signal-to-noise ratio. Primary and auxili~ stations mustmeet requirements for low levels of earth noise andfor reliability as established by the GSE.

A continuous flow of seismic data in digital formfrom the primary stations is transmitted in near realtime to the International Data Center, which is nowlocated in Arlington Virginia but soon will be movedto a permanent site in Vienna, Austria. Seismicarrivals are identified by computer, are associatedwith specific events and then a preliminary locationand size of each event are determined. Once an eventis identified, auxiliary stations are interrogated auto-matically, their data for that event are retrieved andare then incorporated into improved estimates oflocation, origin time and size--typically within a fewhours. Data for each event are then reviewed byseismologists at the IDC for accuracy and consistency;a reviewed event bdletin (MB) is produced in about2 days.

The REB, the final product of the IDC, containsestimates of locations, origin times and sizes (seismicmagnitudes) for each identified event as well asparameters for each station that recorded it such asarrival times of seismic waves and their amplitudes.The MB is accessible over the world-wide web andis available to national data centers for their use inassessing compliance with the CTBT.

During the CTBT negotiations the United Statesand some other countries insisted that the IDC shouldnot issue statements about the nature of detectedevents, i.e. whether they were earthquakes, smallchemical explosions or nuclear explosions. Thatconcept was incorporated in the treaty and its verifica-tion protocol. Thus, the IDC assembles and distrib-utes data but is not permitted to make a judgment ora statement about the nature of events like that ofAugust 16. Judgments of that type are reserved toindividual governments.

U.S. National Data Center

The Air Force Tectilcd Applications Center(AFTAC) operates the U.S. national data center forthe CTBT. Soon tier the U.S.S.R. detonated its firstnuclear explosion in 1949, AFTAC was assigned thetask of operating a secret network of sensors of avariety of types that were installed in various coun-tries. The system is called the Atomic Energy Detec-

tion System (WDS). Its products and assessments ofseismic events as being nuclear explosions or earth-quakes have been and remain classified. AFTACcombines the data flow from the IMS with those fromits classified stations. It also obtains other seismicdata though bilateral agreements. Several of theformer AEDS stations in other countries now provideunclassified data to the IMS.

Under the Treaty, the United States (md othercountries) also are permitted to utilize their ownso-called National Tectilcal Means. These includesatellite imagery, sensors on satellites to detect nu-clear explosions in the atmosphere and space, andother intelligence methods.

Evidence that Event of August 16was an Earthquake

Location of Event at Sea The international networkof seismic stations to monitor the CTBT in northernEurope md adjacent oceanic areas is complete and hasbeen in operation for several years. Figure 3 showsIMS and other seismic stations relevant to tils discus-sion in the area surrounding the Russian test site onNovaya Zemlya. Stations consisting of multiplesensors, i.e. arrays, are indicated by solid triangles. Alarge and sensitive seismic array in southern Norwaycalled Norsar has operated since 1970. Funds for itsoperation and research on its data have come from theNorwegian government and the U.S. Deptiment ofDefense. DoD later provided funds for additionalseismic arrays in northern and southern Norway(ARCESS and NORESS), Finland @INESS),Spitsbergen (SPITS) and Germany (GERESS).Sweden has operated a smrdl but very sensitive arrayat Hagfors (HFS) for several decades. The Russianstations APA and NM are part of the IMS.

The event of August 16 was recorded by thevarious IMS stations in Figwe 1 with the exception ofARCESS, which was being repaired following apower surge. Fortunately, the seismic coverage in thearea has some redundancy. The Finnish station~VO near ARCESS recorded the event, as it hadprevious nuclear explosions at the Novaya Zemlya testsite. Its data are important for the identification of the1997 event man earthquake. ~VO is not one of thedesignated IMS stations. Its recording of that andprevious events points out the great value of drawingupon data from supplementary stations like it when a


Figure 2 Anilia~ seismic stations of the Internation,

“problem event” arises. SOD also recorded the 1997event md some earlier nuclear explosions. Liketise,a new small seismic array at Amderma, which also isnot part of the IMS, should provide key additionddata for events near Novaya Zemlya as it did for asmall earthquake in 1995. Norwegian and Russianseismologists have worked out an arrangement forexchanging data, such as those from Amderrna, APAand stations in Scandinavia.

Locations obtained by the IDC and by the Norwe-gian seismological center Norsar place the August 16event more than 100 km (62 miles) southeast of theunderground nuclear test site at Novaya Zemlya. TheIDC location is shown in Figme 4. On September 15the Associated Press reported results of a classifiedstudy by AFTAC of September 4 about the event. Itquotes a Pentagon spokesperson’ ‘It is a seismic event

approximately 130 kilometers (81 miles) southeast ofthe test sites [sic] and is located offshore.” Thus, thethree agencies each places the event at sea and well tothe southeast of the test site.

On August 21 Dr. Frode Ringdal, the Director ofNorsar and probably the world’s foremost expert onsmall seismic events in and near Novaya Zemlya, senta long fax message about the event of August 16 toDr. Ralph Alewine, Director of the Pentagon’s Nu-clear Treaty Programs Office within the Office of theSecret~ of Defense. Alewine was the only scientistquoted by name in the initial article in the WashingtonTimes. That fax, which was distributed widely,contains the received date and time stamped on allpages. Rlngdal states “Thus the event appears to bequite confidently located offshore and at least 100 kmfrom the test site.” This and other information in thef=, including copies of seismograms, were available

in AleWine’s office a week before the tiicle appearedin the Washington Times, which quotes him by name.

Size of 1997 Event The Washington Post for August29 gives the seismic magnitude of the event as 3.8.Quoting Pentagon officials, the Washington Times onthe 28th states “initial data on the event produced‘high confidence’ that the activity detected was anuclear test equivalent to between 100 tons and 1,000tons of TNT. The relatively small size would beconsistent with tests used to determine the reliabilityof a nuclear weapon. . such as a scaled-down test ofa wmhead primer.” The Reviewed Event Bulletin ofthe IDC gives a seismic magnitude, mb, of 3.9,obtained by averaging readings from two stations.Magnitude is proportional to the log of the amplitudeof seismic waves.

The IDC, which is a sowce of data to national datacenters, however, does not make corrections for whatis commonly howrr in seismology as “station bias.”It only reports uncorrected magnitudes. Rlngdalrecognized about 15 yeas ago that magnitudes calcu-lated for small events often were systematically toohigh. For large events some seismic stations, such asmany of those in Scandinavia, consistently recordseismic amplitudes much larger than the averageobtained from a very large number of stations. As thesize of au event decreases, usually only those fewstations with higher than average amplitudes recordthe event and, hence, report a magnitude. For examp-le, the Norsar array typically recorded amplitudesabout 3 times larger than the average and the Hagforsarray 10 times linger for nuclem explosions at theformer test site of the U.S.S.R. in eastern Kazakhstan.Those biases resulted in magnitudes that were 0.5 and1.0 times lager than the average. The yields of thoseexplosions would have been vastly overestimated ifthey were based on uncorrected magnitudes at thosetwo stations. The phenomenon of magnitude bias iswidely recognized and is comected for by AFTAC andmany others who attempt to make unbiased estimatesof the size of small events.

Large amplitudes of this type resulted from lowattenuation (efficient propagation) of seismic wavesalong paths from eastern Kazakhstan to Scandinavia.For those paths the crest and upper mmtle of the earthnear both sonrce and receiver are geologically veryold, which results in very efficient transmission ofseismic waves. The same is true for paths from


Novaya Zemlya to Scandinavia. The 1997 eventoccurred close to the 1986 earthqtie (Figure 4) forwhich Marshall et al. used station corrections to

obtain mb = 4.26. I used ratios of the seismic ampli-tudes for the 1986 and 1997 events at three Scaudina-viau stations to obtain mb = 3.25 for the 1997 event.Thus, it was about a factor of 10 smaller in amplitudethan the 1986 earthquake.

Using that corrected magnitude and assuming(incorrectly) that the 1997 event was an undergroundnuclear explosion at Novaya Zemlya, the calculatedyield drops to about 50 tons (0.05 kilotons), muchsmaller than the 100 to 1000 tons reported by theWashington Times. The smaller apparent yield issignificant since it is well below the minimum yieldsneeded to reliable test a boosted fission primary for anuclear weapon.

If the event had been a nuclear explosion in thewater, its yield wodd have been smaller, about 10tons since explosions in water couple very efficientlyinto seismic waves. ~lle tiny by the standards ofnuclear weapons, such a yield is much larger than thatof chemical explosions set off at sea for seismicexploration for petroleum.

Identification of Event from Seismic Waves TheWashington Times quotes Alewine “We do haveinformation that a seismic event with explosivecharacteristics occurred in the vicinity of the Russiannuclear test range at Novaya Zemlya on August 16.”The article goes on to state “The Pentagon officialexplained that the explosive characteristics werebased on seismic signals that created ‘very sharp’waves on detection equipment. Waves associatedwith au earthquake ‘do not appear quite sosuddenly’ .“ The last quote is misleading and repre-sents poor seismological practice in seismic identifi-cation. Identification, often called dlscnmination, hasbeen the prime topic of research in nuclear verifica-tion for almost 40 years. A experienced audyst doesnot simple look at a seismogram and pronounce thatit is explosion-like, especially at the regional dlstrmcesof many of the stations that recorded the event ofAugust 16. Various seismic waves are characterizedby “very sharp” signals when they are sampled nearmaxima in the radiation patterns of earthquakes.

Identification is perfomed best by comparingseismograms at a given station for a new event withthose of known previous nearby explosions and

earthqu~es. The earthquake source differs apprecia-bly from that of au explosion in that the formerinvolves shearing motion along a fatit. Consequently,earthquakes typicrdly generate larger shear (S) wavesthan explosions when the two sources are normalizedby the size of the compression first-amiving (P)waves.

The array station ARCESS in northern Norway(Fi~e 3) has one of the best signal-to-noise ratios forevents on and near Novaya Zemlya. It was alsoplaced in operation early enough to record nuclearexplosions at Novaya Zemlya in 1988 and 1990.Ringd4 compared the ratio of SR waves at that arrayfor two explosions and three more recent smallevents. The latter have consistently larger ratios thanthe nuclear explosions, in accord with those threeevents being etiquakes. Two of those three eventswere located more than 200 km north of the test site(Figure 4).

Since ARCESS was not operating on August 16,the nearby station KEVO can be examined in thesame way. In his fax to Alewine, Rlngdal comparesthe record at KEVO for the 1997 event with thosefrom three previous nuclear explosions at NovayaZemlya. The event of 1997 flso efilbits a higher S/Pratio th~ the nuclear explosions, again being indica-tive of its being an earthquake. British seismologistsobtained a similar result for KEVO and for anotherstation in Finland. My colleagues Richards and Kimof Columbia performed a quantitative analysis of theS/P ratio as a function of frequency at KEVO. Thatratio for the 1997 event is significantly higher thanthat for three nuclear explosions at Novaya Zemlya.Their result is in excellent accord with recentlypublished work by them using the same methodologywherein they found good separation between thoseratios for explosions and earthquakes elsewhere.Thus, careful audyses of seismograms indicate thatthe event of August 16 was an earthquake at a Klghlevel of confidence.

One misleading quote in the Washington Timesstates “monitoring equipment also indicated the depthof the suspected test was zero -- which does not fitwith an underwater earthquake.” Since data hornstations very close to the event were not available, thedepth was arbitrarily fixed at zero, not calculated, acommon practice for small shallow earthquakes witha similar distribution of recording stations. The datalikely would be consistent with an event anywhere in


the outer 30 km of the earth. Thus, the depth useddoes not permit identification u either an explosion orearthquake. For larger shallow events depth can becalculated more accurately, A careful comparison ofthe seismic waveforms of the nearby events of 1986and 1997 may permit the depth of the 1997 event tobe ascertained.

Why did Some Responsible U.S. OfficialsConclude that the 1997 Event

was a Nuclear Explosion?

The Washington Times stated that satellite photo-graphs of the Russian test facility prior to August 16indicated the movement of trucks and other activitiesthat in the past were seen prior to nuclear test explo-sions. The Washington Post of August 29 remarksthat intelligence satellite data indicated that Russianscientists had been unusually active at the test site inthe preceding few months. It states further “Tectil-cians there have been flying around in helicopters,lowering equipment, plugging test holes and stringingcables for diagnostic equipment, according to severalsources. Victor Mikbailov, Russia’s minister ofatomic energy, visited the site several weeks ago.Russian officials have explained that they are con-ducting or preparing to conduct ‘sub-critical’ nucleartests, in which chemical explosions are used to blowapart fissile material but no nuclear chain reactionoccurs.”

The United States conducted two sub-criticalnuclear test underground at the Nevada Test Site@TS) in 1997. Plutonium is involved in thoseexperiments as is the firing of the chemical explosivesin a nuclear weapon. Probably similar equipment tothat used for secure trmsport of fissile materials andfor monitoring past nuclear tests also is used by boththe US. and Russia for sub-critical tests. Such testsare not prohibited by the CTBT even though someargue that they violate the spirit of the Treaty. Ironi-cally, a small earthquake, somewhat larger than theAugust 16 event, occurred at NTS as the U.S. waspreparing to conduct its second sub-critical test.

These press reports indicate that intelligence dataas well as seismic observations were involved in theaccusations of Russian clandestine nuclear testing.Mile much information remains classified, thefollowing scenario of U.S. response to the event ofAugust 16 can be reconstructed from press reports md

unclassified data, The Russians were preparing toconduct a sub-critical test (or may have alreadycompleted such a test) when a small earthquakeoccurred off the coast of Novaya Zemlya. Someofficial(s) in the Defense Department and perhaps inthe intelligence community jumped to the conclusionthat the earthquake was a nuclear explosion.

The story then was leaked to the WashingtonTimes and published 12 days after the event. By thattime, however, the fax from Ringdal in Norway hadalready been in AIewine’s office a week, indicatingthe event was more than 100 km from the test site.Also, the seismograms in his fax for the stationKEVO indicated that the event had the characteristicsof an earthquake and not those of an explosion.Nevertheless, Alewine and others furnished informa-tion to the Washington Times that was out of date byat least a week and was misleading and deceptive.

The AP stow on the classified AFTAC report ofSeptember 4 “indicates the tremor was probably anatural earthquake.” Sometime in early September anaftershock was identified that occurred 4 hours afterthe August 16 event. Nevertheless, as of September22, when President Clinton spoke at the UN, highU.S. officisds still claimed that the event may havebeen either an explosion or au earthquake.

As the reality of au offshore location becameevident, however, some invoked a number of old mddiscredited evasion scenarios including either con-ducting a small nuclear explosion at the test siteimmediately after the earthquake or detonating twosmall nuclea devices (one at the time of mainshockand another at that of the aftershock). In the latterscenario the Russians are assumed to have emplacedthe two nuclear weapons sometime earlier in holesdrilled into the seafloor.

In a follow-up story on August 30, Bill Geti, theNational Security Correspondent of the WashingtonTimes, states “Suspicions that Russia secretly carriedout a small underground nuclear test two weeks agohave raised new questions about whether the signedbut unratified test ban treaty cm be verified effec-tively.” I tilnk that discrediting the verifiability of theCTBT is the overriding motive for the leaks to thepress about a suspicious nuclear test on August. Ihave long thought that questions of verifiability wouldbe central to the debate about the ratification of theCTBT.

Alewine rmd others in the Defense Department


argued for many years that the U.S.S.R. had detonatednuclear explosions far in excess of the 150-kt limit ofthe bilateral Threshold Test Ban Treaty (TTBT) of1974. Soon after the TTBT was signed, two leadingseismologists at AFTAC, Thomas Elsenbauer andRobert Zavadil, found evidence from seismic sarfacewaves indicating the offici~ forrmda used by the U.S.to estimate yields of Soviet nuclear explosions fromP waves gave calculated yields that were too large.They were strongly opposed by AFTAC and otherDoD officials. I was a member of an AFTAC panelthat reviewed their work and other methodologies forestimating yields of Soviet explosions in the late1970s. men a majority of the panel concluded thatthe existing formula, in fact, was generating yieldsthat were too large, the panel was never asked to meetagain. Testing above the limit of the TTBT was oneof several arms control agreements the U.S.S.R. wasaccused of violating during the Reagm and Bush eras.

Questions of Soviet cheating on the TTBT wereallowed to simmer and remain wesolved for adecade until Congress authorized its Office of Tech-nology Assessment to conduct a study of both Sovietcompliance tith the TTBT and verification of aCTBT. The OTA Report of 1988 found no evidencethat the Soviet Union had detonated nuclear explo-sions above the 150-kt limit of the TTBT. The issuewas finally resolved when the U. S. and the U.S.S.R.each conducted a nuclear explosion with a yield closeto the threshold and allowed the other to monitor itvery close to the shot point.

mile research on seismic verification of under-ground nuclear testing had gone on since 1958, thestatus of verifiing a CTBT and the TTBT were notreviewed by au independent agency until the 1988OTA study. Throughout the past 40 years agenciesthat have opposed a CTBT have had to wdk a finefine between working to acquire excellent intelhgenceinformation but at the same time arguing that data andinstrumentation were not good enough to verify aCTBT.

At one point in the yield debate, an AFTACofficial stated that they had not been ‘tike& to workon improved estimates of yield. I am very concernedthat the present debate about Russian comphance withthe CTBT resembles the long arguments about theyields of Soviet nuclear explosions under the TTBT.For example, AFTAC has shown little interest inincorporating seismic data from supplementaryseismic stations such as very sensitive ones in

Kazakhstan, many of which recorded the August 16event and previous small earthquakes near NovayaZemlya. Alewine’s office has gained control of mostfunding for seismic research on verification of theCTBT and has driven the Air Force Office of Scien-tific Research and the Phillips Lab of the Alr Forceout of the field.

In contrast, for nearly 40 years a small group ofBritish seismologists who work on seismic verifica-tion has conducted and published excellent studies ofa few key problem events, such as demonstrating thata seismic event at the eastern Kazakhstan test site inMarch 1976 was a smrdl earthquake. They have t&ena strong scientific and problem-solving approach ashave the Norwegians. Intense studies of a few key“problem events” does advance the field of nuclear

verification. The New York Times article of August29 states “An administration official, speaking oncondition of anonymity, said Britain and Norway, forexample, dso saw the data [on the event of August16] and had not suspected a nuclear explosion? Thusfar, the U.S. Government has taken a different posi-tion on that event than its two NATO allies, Norwayand the U.K, each of whom have some of the mostknowledgeable seismic verification teams.

Other Small Earthquakeson and near Novaya Zemlya

The event of August 16, 1997 is, in fact, the 4th of5 small seismic events on and near Novaya Zemlyathat has been declared to be either a suspicious or aproblem event by officials of the U. S. DefenseDepartment. ARer detailed study, all 5 subsequentlywere identified as earthquakes. Novaya Zemlya andsurrounding waters is an area of low natural eA-quake activity, a so-called intraplate region in theparlance of plate tectonics. Its level of natural activityis somewhat lower than that of the 300 km by 300 kmregion centered on New York City.

Several smrdl seismic events occurred near theshot points of two megaton-size underground nuclearexplosions in 1973 and 1974 and were undoubtedlyeither earthquakes triggered by the explosions them-selves or signals resulting from the collapse of under-ground cavities created by those explosions. Other-wise, no earthquake had ever been detected on or nearNovaya Zemlya until the occurrence of a small eventon August 1, 1986. An official of the Defense Ad-vanced Research Projects Agency (ARPA), Dr. Alan


Ryan, concluded that the 1986 event could not beidentified positively and that the large 90°/0 confi-dence region associated with its location included landareas of Novaya Zemlya. ARPA previously directedthe nuclear verification office for DoD. The eventoccurred at a time the U.S.S.R. had stated that it wasobserving a self-declared moratorium on nucleartesting. Ryan’s 90% confidence region, however, didnot include the Soviet underground test site, whichoccupies a very small area of Novaya Zemlya (Figure4).

In 1989 three British seismologists published adetailed study of the 1986 event. Based on a numberof criteria, they concluded that it was an earthqtie ata depth of 24 km within the crust. By carefullycalibrating travel times of seismic waves in the region,they obtained the location shown in Figure 4 and amuch smaller 90°/0 confidence region that was entirelyat sea. Their revised seismic magnitude, mb, of 4.26,which was corrected for station bias, was smaller thanones based on uncorrected and fewer values of mb.The depth of 24 km is important since it indicates theevent was of natural origin. (Most undergroundnuclear explosions have been detonated at depthsshallower than 1.5 km; the deepest, at a depth of about4 km. With the exception of one super-deep well to13 km, the deepest wells drilled reach depths of 10km.)

Figure 4 shows four subsequent small events inand near Novaya Zemlya with their seismic magni-tudes in parentheses. The smallest of these, the eventof January 1996, was featured twice in the Washing-ton Times by Bill Gertz under the headlines “U.S.Officials suspect Russia staged nuclear tests this year”and “Perry cites evidence of Russian nuke test.”William J. Perry was then the Secretary of Defense.Au anonymous source was quoted as saying “It was alow-yield test in mid-January”. As in the WashingtonTimes article of August 28, the two stories on the1996 event inferred that the intelligence communitybased their suspicions on observed activities at theNovaya Zemlya test site that were similar to thoseseen during a nuclear weapons test. The reportsoccurred at a critical time in the test ban negotiationsand at a time Russia had announced that it was fol-lowing a moratorium on nuclear testing (but notnecessarily on sub-critical tests).

In his first article on the 1997 event Gertz statesthat U.S. officials were unable to prove the 1996 eventwas a nuclear test at Novaya Zemlya. Nevertheless,

Figure3 Seismic statiom in northern Europe relevant to studies

of seismic events at Novqa Zemlya.

the Washington Post article of August 29, 1997 states“After raising concerns with Moscow about anothersuspicious signal in early 1996, the Clinton adminis-tration determined that it had been caused by anefiquake.” We need to know the basis for the latterdetermination. As stated earlier, Ringdd showed thatthe small events of 1992, 1995 and 1996 in Figure 4had S~ ratios at the ARCESS seismic array thatdiffered appreciably from those of past nuclear explo-sions at the Russian test site. Fisk obtained a similarresult for the 1992 event.

In 1993 ARPA hired several consulting firms toexamine the 1992 event, probably at a cost of severalmillion dollars. While special studies of “problemevents” do advance the subject of nucleas verification,it is questionable if so much money should have beenspent on an event so small, Residents of Californiawill recognize that an earthquake of magnitude 2.7 isa very small event, one that is rarely felt by anyone.In his executive summary of 1993 about the 1992event, Ryan states that its magnitude was appropriatefor a folly-decoupled 1 kiloton nuclear test. This begsthe question Is fully decoupled or highly decouplednuclear testing possible at Novaya Zemlya?

In a 1996 review paper on decoupled nucleartesting I argued that lasge decoupling factors could beobtained only for explosions with yields in excess of1 kiloton when they were detonated in huge cavitiesconstructed in salt domes. The decoupling factor isthe amplitude ratio of a well-coupled, non-evasiveexplosion to that of one of the same yield detonated soas to decouple or muffle the size of its seismic waves,Large cavities constructed in hard rock and used for


clandestine nuclear tests are likely to leakbomb-produced radioactive isotopes to the surface byway of joints and faults. Hard rock contains suchimperfections on a scale of meters and larger. Acavity tith a radius of about 28 meters and at a depthof 1 km in sdt is needed to fully decouple a 1 kilotonnuclear explosion. No sak domes are known beneathNovaya Zemlya. Since few people live there andmining is rare, attempts to create a large cavity in anyrock type should be readily observable with satelliteimagery.

The United States stated in a working paper forthe CTBT negotiations that it desireda monitoring capability of “a few kilo-tons, evasively tested.” Hence,whether large decoupling factors (like70 times) can be achieved or not by apotential evader drives monitoringperceptions. A few kilotons testedwith a decoupling factor of 70 timescorresponds to an mb of about 3.0. Acapability better than that is beingachieved now for Novaya Zemlya.Probably decoupling factors no largerthan a factor of two, however, arepossible at that test site for yields of afew kilotons. An explosion of thatsize would correspond to mb 4.0.Thus, of the 5 small earthquakes inand near Novaya Zemlya of the last 11years, only that of 1986 was largeenough to have an mb value compara-ble to that of an explosion of a fewkilotons evasively tested.

The real question that needs to bedebated is Were any of the subsequentsmall events on or near Novaya

ftiher north than the northernmost point in Alaska.It is a tilgid, largely mountainous region where polarbears are more numerous than humans. Much of itsnorthern half is covered by glaciers. The rest is justemerging from the last glacial age. It is dark continu-ously for several months there and winter lasts a longtime. Except for glacial action, the last major geologi-cal event in the area occurred more thmr 250 millionyears ago. This rules out one suggestion made in aPentagon press briefing that the event of August 16might have been an uudewater volcanic eruption.

The Soviet Union conducted its largest nuclear

Figure 4 Locations and their 90%

confidence limits for 5 smallearthquakes on and near Novqa

Zemlya. The seismic magnitude, mb, is

shown in parentheses beside the date ofeach went. Results for 1997 mentpornIDC; that for 1986fiom Mmshall

et al.; others f~om Ringdal.

Zemlya large enough to constitute cheating of militarysignificance if they had been explosions? Leakingstories to the press about the smallest event, that ofmb 2.4 of 1996, appears to be making a mountain outof a molehill, especially when the event was locatedmore than 200 km from the Russian test site. Furtheranalysis showed that it was an earthquake.

WorMng in Novaya Zemlya:the Dominant Influence of Climate

The Novaya Zemlya test site at latitude 73° N is

explosions at Novaya Zemlya prior tothe entry into force of the ThresholdTreaty in 1976. Many of those explo-sions appear to have been tests ofnuclear weapons that could not beconducted at full yield at the moreaccessible test site in easternKazakhstan. Likewise, the UnitedStates was forced to go to remoteAmchhka Island in the western Aleu-tians to conduct its largestunderground nuclear explosion toavoid causing damage in Las Vegas ifit had been detonated at the NevadaTest Site.

The U.S.S.R. has published infor-mation on 42 mdergrouud nucleaexplosions conducted at NovayaZemlya. All but two were detonatedbetween July 27 and Nov. 7. Nonewere conducted between Dec. 4 andMay 7. This pattern is obviously con-nected to the long, harsh winter condi-tions in Novaya Zemlya. Why didn’tsome officials in the United States at

least stop to ask Doesn’t it seem unlikely that Russiawodd detonate tiny nuclear explosions--those of Dec.31, 1992 and Jan. 13, 1996 and the smallest eventsdetected thus far--in the midst of severe Arctic wintercondhions? Fortunately, seismic networks stronglysupport the most obvious explanation, i.e. they weresmall earthquakes.

Conclusions

I have presented several lines of evidence that the

seismic event of August 16, 1997 was a small earth-


quake. It occurrence was not unique since it was the5th known small earthquake to occur on or nearNovaya Zemlya since 1986. In four of those casesofficials of the Defense Department stated soon aftertheir detection that each was either a suspiciousnuclear explosion or au event of ambiguous origin. Ineach case special studies of the locations and wavecharacter indicate that they were earthquakes, notexplosions.

Information on the events of 1996 and 1997 wereleaked to the Washington Times and headlined assuspicious nuclear explosions. The 1996 earthquakeoccurred at a critical time in the negotiations for theTest Bm Treaty and the latest as the Treaty was aboutto be conveyed to the Senate for ratification. Muchmisinformation was given to the press in conjunctionwith the stories that appeared on August 28 and 29.Information that the event was located well at sea andat least 100 km from the test site was available in theNuclear Treaty Programs Office of DoD a weekbefore the story broke in the Waskingimr Times.While the role of the intelligence agencies in thisaffair remains classified, the press reports cite whatthey claim is detailed intelligence information bearing

upon a nuclear origin. It seems likely that prepara-tions were being made to conduct a sub-criticalexperiment at the test site at roughly the same time asmall earthquake occurred offshore. An uucriticd andrushed judgment was made that the earthquake was anuclear explosion.

This experience shows that existing internationalseismic monitoring stations as supplemented by datafrom other key stations did provide sufficient informa-tion to identifi not ody the most recent event but dsofour previous small events as earthquakes. Unfortu-nately, as of late September high officials in the U. S.Govermnent still had not acknowledged tils rmd werecltiming that the 1997 event had not been determinedto be either an explosion or au earthquake. If thesestatements of ambiguity continue, the Test Ban Treatylikely will fail to win ratification in the Senate.

Clearly, investigations are needed both within theexecutive and legislative branches of the governmentto ascertain who misled both the press and publicofficials about the nature of the event. A technicrdlysophisticated, thorough, non-ideologicd, and honestreview process needs to be established within thegovernment for CTBT verification that involves avariety of agencies with test ban responsibilities. For

more than 40 years several DoD officials in nuclearmonitoring have been strong opponents of a CTBTeven though they were chaged with either using orimproving verification methods. The August 16 eventdemonstrates that this subject now has such seriousforeign policy consequences that those with thehidden agenda of opposing a CTBT cannot be allowedto make poor and rushed tectilcal judgments and thenleak them to the media. The United States riskscrying wolf too many times. We need to save ourcredibility for the case of a possible nuclear explosionthat is a breach of the Treaty. Two NATO allies whopossess outstanding groups in seismic verification dldtheir “homeworp on the 5 Novaya Zemlya events mdshowed that they were not of nuclear origin. They didthis with fewer people and less fuding than theUnited States. While instruments and identificationmethods performed well for the August 16 event, thehuman part of the system in the U.S. did not. Weneed the help of the Defense Department and theintelligence agencies in verifying a CTBT but wemust insist on analyses with the highest standards.

Confidence Building Measures Several confidencebuilding measures could help prevent false alarmsunder the CTBT regime. These could be a combina-tion of bilateral and multinational agreements. This isespecially important as long as the Treaty remainsunratified, which is likely to be so for at least severalyears until all 44 stipulated countries that have thecapacity to produce fissile materirds sign and ratifi theTreaty. While much of the International MonitoringSystem (IMS) is likely to be in operation before then,provisions for on-site inspections do not formallybecome effective until the Treaty enters into force.

1. Conduct announced chemical explosions withyields of about 20 to 50 tons at the Nevada, NovayaZemlya and Lop Nor test sites with observers presentfrom the countries involved in the agreements. Thiswould permit calibration of the locations of seismicevents detected at and near those sites. More impor-tmtly, it would allow those sensitive stations of theIMS that were placed in operation after the lastnuclear explosions in various areas to be calibrated sothat their data can be used more effectively for identi-fication of future events. The United States has plansto conduct chemical explosions in that size range atthe Nevada Test Site. Chemical explosions of thatsize at Novaya Zemlya would undoubtedly arouse


U.S. suspicions if U.S. witnesses were not present.Chemical explosions for calibration purposes, in fact,were conducted in 1997 at the former test site ineastern Kzakhstan.

2. Exchange data on past chemical explosions andetihquakes at and near those three test sites. At leasttwo large chemical explosions are known to havebeen conducted at the Novaya Zemlya test site. NTSand Lop Nor have higher levels of natural earthquakeactivity than Novaya Zemlya.

3. Arrange for rapid exchange of data from seis-mic and other stations that are not part of the IMSwhen a “problem event” occurs.

4. Install seismic stations at or near each of thosethree test sites whose data can be transmitted to otherparties in near real time.

5. Consider halting sub-critical experiments at alltest sites to avoid their being mistaken for a nuclearexplosion of small yield. ~ether China would joinsuch a venture is unknown.

Data Availabih~ in the U.S. The accessibility of theReviewed Event Bulletin of the IDC permitted U.S.seismologists outside of AFTAC to quic~y access thelocation ad size of the event of August 16 once itwas announced in the press. Identifying an event aseither an explosion or earthquake (other tha by alocation at sea), requires access to seismograms, alevel of data above that contained in the ~B. As theU.S. national data center for the CTBT, AFTAC hasstated for more than two years its intention to makeseismic data from the unclassified stations of the IMSpublicly available. Thus fa, however, AFTAC onlymakes data available for three U.S. seismic stations.

FASPUBLICINTERESTREPORT(202)546-3300307 Mass.Ave.,N.E., Washington, D.C. 20002ReturnPostageGuaranteedNovemberDecember1997.Volume50. No. 6

I

In 1996a report published by the National Academyof Sciences~ationd Research Council stronglyrecommended that unclassified data from the IMS bemade available to U.S. scientists. Those data areavailable to users in many other countries. The CTBTprotocol only stipulates that data from the IDC bedistributed to all national data centers for the CTBTthat request them. The national data centers for theUnited States and Russia have standing orders toobtain dl data transmitted to the IDC. Many U.S.seismologists were unable to get unclassified data onthe August 16 event through tie U.S. national datacenter.

Fortunately, the data from KEVO, Finland, anon-IMS station whose data were critical in identi&-ing the August 16 event as au earthquake, werereadily available through the data center operated bythe U.S. consortium for seismology called INS. Thefield of seismology, which has been involved inearthqu&e studies for nearly 100 years, has a longtradition of international data exchange, much likethat for weather information. Seismic data havemultiple uses--nuclear test verification, quick andaccurate location of damaging earthquakes so as topermit rapid emergency response and studies of theinterior of the earth rmd the physics of the earthquake

source. It would be a tragedy if unclassified seismicdata from other countries were not available in theUnited States when a major earthqtie disaster strikessomewhere else in tie world and U.S. response to thedisaster were delayed. Hopefilly, the experience withthe seismic event of August 16 will finally result ineasy access to unclassified seismic data.

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