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Critics fault the seismic detection system for missing one announced Indian blast and are trying to cut its budget, but seismologists believe the test didn't match India's claims
Seismologists who watch for tremors caused by nuclear tests are puzzling over a problem like one that intrigued Sherlock Holmes: the dog that didn't bark in the night. In their case, the watchdog is a sprawling web of sensors that encircles the globe, programmed to monitor compliance with the Comprehensive Test Ban Treaty (CTBT). It sounded an alarm on 11 May, when India set off a cluster of underground bomb tests. But on 13 May, the same system remained strangely silent at a time when the Indian government claimed to have detonated another set of nuclear explosions equal to 800 tons of TNT. The sensors saw and reported nothing.
The network's apparent failure to detect all of India's explosions has given ammunition to those in Congress who oppose the treaty and led critics to argue that the seismic network can't be trusted to detect small tests. For example, the Center for Security Policy in Washington, D.C., headed by CTBT critic Frank Gaffney, said on 19 May: "It has now been established that if India (or other nations) wish[es] to conduct nuclear tests in the futureeven after pledging not to do sothey can be reasonably sure of getting away with it."
But a strong consensus has emerged among U.S. seismologists that the system in fact worked well. It immediately and convincingly detected the 11 May Indian blasts and those set off by Pakistan on 28 and 30 May. And, based on that performance, a dozen specialists consulted by Science-from both government and private labs-say that even though the system's design limit is 1000 tons, it should easily have detected the claimed 800-ton blast on 13 May. Indeed, most believe a blast as small as 100 to 200 tons would have been picked up. Says geophysicist Hans Hartse of the Los Alamos National Laboratory in New Mexico, "[India's] claim of 800 tons would have been visible all over the world."
This has led some experts to suggest that the 13 May tests may have been at most small subcritical blasts fueled by chemical explosives-"hydrodynamic" experiments of the type...