'A small event'

THE global network that tracks earthquakes and underground atomic blasts found only a faint echo from the nuclear test that Pakistan said it conducted on May 30, experts in the United States said.

That could mean that the test was successful but small or that the test was a failure and produced relatively few shock waves. "It's a small event," said Terry Wallace, a seismologist at the University of Arizona who works with the Incorporated Research Institutions for Seismology, a scientific group in Washington. Wallace said that the blast had a preliminary magnitude of 4.3, equal to about 1,000 tons of high explosive. By contrast, the atomic bomb dropped on Hiroshima in 1945 had an explosive force of 15,000 tons.

The main Pakistani blast on May 28 was monitored as having a magnitude of 4.8, equal to 8,000 to 15,000 tons. Such bombs are considered relatively small by the standards of world arsenals, where the explosive power of warheads can exceed millions of tons.

The May 30 test was too small to show up on the U.S. Government's main network for monitoring earthquakes around the world. "We've searched everything we have and we don't see anything," said a spokesman at the National Earthquake Informational Centre, in Colorado. "We didn't record anything at all."

Both groups of scientists said that they would continue to examine data as it came in and held out the possibility that more faint signals from the Pakistani test site might be uncovered.

New York Times Service