American scientists monitoring remote sites where India and Pakistan detonated nuclear devices sharply question public claims by both nations about the size and number of weapons tested.
Scientists examining seismic data on the tests, picked up at monitoring stations around the globe, say that both India and Pakistan have exaggerated the explosive power of the detonations and perhaps even the total number of devices tested. The Clinton administration has similar doubts about the claims by the Southwest Asian rivals.
Pakistani officials apparently disconnected a seismic monitor that would have given outsiders more precise data about their tests. And two nuclear devices that India claimed to have set off were not detected by a single known seismic monitoring station anywhere in the world.
“We’re looking at regional hyperbole,” said Terry Wallace, a geophysicist at the University of Arizona and an expert in measuring nuclear explosions. “Clearly the size of the explosions are overstated.”
The gap between the claims and the seismic data suggests that the tests may not have gone as well as each side announced, said experts interviewed by the Tribune. Their findings raise questions about India’s claims to have successfully tested devices for a range of capabilities, from low-yield fission devices to potentially city-destroying thermonuclear, or hydrogen, bombs.
The discrepancies in monitoring data also provide ammunition for some critics of an international test ban treaty. These critics argue that the lack of data for India’s announced second round of nuclear weapons tests calls into question whether clandestine nuclear tests can be accurately monitored.
Experts caution that it is impossible from seismic data alone to draw conclusions about the sophistication of the Indian and Pakistani nuclear programs or about how quickly the two nations may produce the actual nuclear weapons deployed on missiles and aircraft, a step the United States and other major nuclear powers hope to avert.
Evidence emerging over the last few days suggests, however, that neither country may be providing an accurate picture of the extent of the explosions they set off underground last month.
Based on seismic readings of the detonations, experts estimate that the first announced round of nuclear tests by India on May 11 produced shock waves equivalent to an earthquake of 4.7 to 5.4 on the seismic scale.
This translates into a blast totaling 25 to 30 kilotons, about twice the explosive force of the atomic bomb the U.S. dropped on the Japanese city of Hiroshima in World War II.
However, India claimed it conducted the equivalent of a 55-kiloton explosion by detonating three devices.
In its second announced round of tests two days later, India claimed to have detonated two small nuclear devices, but no shock waves registered at any known monitoring station, scientists say. This raises the possibilities that the second Indian test was a hoax, a failure or too small to register on the international scientific network of seismographs that can detect most nuclear tests.
In Pakistan’s case, the announced blast May 28 was less than half the 35 kilotons claimed, experts say. A kiloton is roughly equivalent to 1,000 tons of TNT. The atomic bomb dropped on Hiroshima in 1945 had an explosive force of 15 kilotons.
Estimating yields from the outside without access to the test sites or the test data is a tricky science. Shock waves can be muffled by a variety of factors, including the geological features surrounding the test location.
The design of the test site–for example, whether the device is placed in a deep hole or a mountain tunnel–also influences the shock wave pattern.
Nonetheless, American scientists strongly question India’s claim that it successfully set off a thermonuclear device, a powerful and sophisticated hydrogen fusion bomb. Such a bomb could be targeted at cities and wreak massive destruction. But the seismic evidence supporting the claim is ambiguous, at best.
More Top Picks Shun Classic 8
The Indian government said the blast for the thermonuclear device measured 43 kilotons. But the lower estimates for the total yield of the announced first round of Indian tests leads some experts to question whether India has, in fact, mastered the technical challenge of a fusion bomb.
India said the shock waves might have been dampened somewhat by the simultaneous explosion of two other devices. However, some scientists question whether more than one device was set off.
If the data is ambiguous, U.S. geologists say they have a solid understanding of the geology of the Indian desert test site. “If they had set off that 43-kiloton device at the depth they said, it should have produced more of a disturbance,” said Columbia University geophysicist Lynne Sykes.
Some weapons experts say it is possible that India did explode a hydrogen bomb and overstated the yield for political effect. “You cannot disprove the claim with the seismic information,” said David Albright, a nuclear weapons expert with the Institute for Science and International Security. “I have come to believe, based on other evidence, that they detonated an H-bomb.”
This other evidence, he said, included statements by Indian scientists in recent years about development of a hydrogen bomb.
The first Indian tests registered unmistakably at a seismic monitoring station at Nilore in neighboring Pakistan. The station is the closest to both the Indian and Pakistani test sites and is operated jointly by Pakistani scientists and the Scripps Institution of Oceanography in San Diego, Calif.
However, the monitoring equipment in Nilore, Pakistan, was disconnected from a satellite data link two hours before the Pakistani test on May 28, according to Professor Jon Berger, a Scripps researcher. The sensor remains disconnected, he said in an interview Thursday.
The data some American scientists are using on the Indian and Pakistani tests come from a global network of monitoring equipment whose information is available to the public. The Pakistani tests, for example, registered at stations as far away as Texas, according to the U.S. Geologic Survey.
For decades, the U.S. government has maintained a separate, sophisticated web of detection equipment that produces classified information for American policymakers. This monitoring system is capable of measuring minute shock waves, sniffing the air for radioactive particles, and taking satellite pictures of test craters. A classified U.S. government assessment of the Indian and Pakistani tests was sent to Congress Wednesday.
Both sets of tests conducted by Pakistan showed up on the publicly scrutinized network of seismographs, but the blasts were probably of significantly lower yields than the Islamabad government claimed, some scientists say. Instead of 35 kilotons, the first Pakistani explosion on May 28 is estimated at no more than 15 kilotons, while the second on May 30 was only between 3 and 6 kilotons, these experts say.
The two rounds of Pakistani tests occurred at sites some 45 miles apart, at previously unknown tests sites. Because of the unfamiliar geology there, some experts are less confident about their estimates of the Pakistani tests than in the case of the Indian explosions.
“It’s possible that the Pakistani blasts might be damped a little bit (by the geology of the test site), but they are unmistakably smaller than the Indian events,” said Jeffrey Park, a Yale University geophysicist.
Judging from publicly available data, scientists said it was unclear how many individual nuclear devices were set off by both countries. India claims to have conducted five detonations, three the first day and two the second. Pakistan officials have claimed six.
Both could have set multiple explosions at once, which would be recorded as one blast. That has the effect of masking the size of the individual explosions.
Berger, for example, said the data on the three, first-day tests India claimed was inconclusive. “I saw a seismic event which was consistent with a single test,” said Berger.
The Pakistani tests were recorded as a complex shock wave pattern, other scientists said, which suggests multiple explosions within seconds of one another.
“They might have set multiple blasts off at the same time,” said Stuart Koyanagi, a geophysicist for the U.S. Geological Survey. “If that’s the case, then the signature from the Pakistan blast, for example, might have contained material from more than one blast.”
The spate of nuclear tests in Southwest Asia has sharpened a debate that has been under way for years about whether it is possible to effectively detect small nuclear tests by governments less interested than India and Pakistan in letting the world know about their activities.
The Comprehensive Test Ban Treaty, which prohibits signatory countries from conducting nuclear tests, relies on the assumption that cheaters can be detected if they detonate all but the smallest of nuclear devices.
The treaty, which has been signed by more than 190 nations but has yet to take effect, contains provisions beefing up the worldwide network of seismographs, radiation detectors, satellites and other monitoring equipment to make cheating more difficult. The U.S. is a signatory to the treaty, but the Senate has not ratified the accord, and Republicans say they are unlikely to consider it any time soon.
Under the treaty, a country suspected of conducting a secret test is subject to international inspection. Supporters, pointing to the wealth of data available about the Indian and Pakistani tests, say it proves that governments tempted to covertly test in violation of the test ban will be detected. Tests of 100 tons or even less are easily picked up in many parts of the world, including India and Pakistan, experts say.
Opponents point to the second day of Indian tests, when seismic monitors picked up no sign of what India said were tests of two devices of less than a kiloton each, one with a yield of 600 tons and another with a yield of 200 tons. If India managed to detonate a device without detection, they say, it underscores the problems with verifying the proposed test ban accord.
A test ban opponent, Kathleen C. Bailey, assistant director of the Arms Control and Disarmament Agency during the Bush administration, said in an interview that current technology can guarantee detection only of tests with yields higher than 500 tons.
“It’s really not possible to improve things with current technology to an order where we can consistently and effectively verify a comprehensive test ban,” Bailey said.
———-
MORE ON THE INTERNET:
Keep up with developments in Pakistan and India at chicago.tribune.com/go/nukes
More Top Picks Best Shower Filters For Well Water