Having detected renewed activity at the old Soviet underground nuclear test site on the island of Novaya Zemlya, U.S. intelligence was understandably alarmed when reports were received of a seismic event whose initial location was deemed sufficiently uncertain to possibly include the test site. As more information became available, however, both U.S. government seismologists and the international seismological community concluded that the event had occurred 130 kilometers from the test site and beneath the bottom of the Arctic Ocean. The location alone should have established that it was a natural earthquake unrelated to the test site activity. But the CIA continued to insist that the event could be a nuclear explosion despite a growing consensus among U.S. and foreign seismologists, working with open data, that the seismic signals were consistent with those from earthquakes and similar to a small earthquake recorded previously in the same general area. Moreover, a very small aftershock, characteristic of an earthquake, had occurred several hours after the main event at the same location. For its part, the Russian government promptly denied there had been a nuclear test and explained that activity at the Novaya Zemlya site related to permitted subcritical tests similar to those being conducted concurrently at the U.S. test site in Nevada.
In the end, Director of Central Intelligence George Tenet, unable to resolve the issue internally, convened an outside panel which concluded that the event was indeed not a nuclear explosion. Unfortunately, the panel inexplicably avoided identifying the event unambiguously as an earthquake, an evasion that incorrectly left a misleading impression about the capabilities of the regime's international monitoring system. The CIA's failure to take a clear stand on the nature of the event is most unfortunate given the critical importance of the powerful array of U.S. national intelligence assets to the discovery of potentially suspicious activities relating to any of the very large number of natural seismic events that occur (averaging some 50 a day more powerful than the recent event). Suspicious activities, however, do not turn an earthquake into a nuclear explosion. To insist that seismic events may be nuclear tests when the technical information available to the international community demonstrates the contrary undercuts the credibility of U.S. intelligence, which is rightfully internationally respected and will be critical to marshaling support to respond to suspected clandestine tests under the CTB Treaty.
The lesson of the August 16 event is not, as the CIA emphasized in its statement, that very small seismic events are hard to identify, which is well known, but rather that the capability exists to verify the CTB effectively. Even before becoming fully operational, the international monitoring system was able to locate the event accurately and identify it as an earthquake with an equivalent yield of around 100 tons of TNT, or one tenth the system's advertised identification threshold of 1 kiloton, as well as an aftershock of around 10 tons, or one hundredth of the identification threshold. At such low yields, undetected tests would not constitute a threat to U.S. security. Such tests would not give the nuclear powers confidence in new designs for higher yield weapons and would not provide potential proliferators with an exploitable path to a first weapon. Moreover, the success of U.S. intelligence capabilities in detecting activities at the Novaya Zemlya test site should help deter others because such activity collocated with a truly suspicious seismic event or other incriminating information would indeed be persuasive evidence of a nuclear test.
The CTB regime successfully passed the test presented by the August 16 earthquake, demonstrating its effectiveness and underscoring the imperative of maintaining the international credibility of U.S. intelligence as a central input to verification of the CTB Treaty. The power and objectivity of this unique U.S. capability must not be called into question by crying wolf when other countries are capable of judging for themselves whether there are any wolves or by failing in the future to draw obvious conclusions about treaty compliance when the evidence is clear.