US scientists doubt Pokhran test data

No signal consistent with a test was found for as much as six hours before and after the announced time in the Hindukush region.

Based on this and analysis of noise levels over a wide range of frequencies, the team has concluded that seismic magnitude of the May 13 event was 8220;at least 500 times smaller than theMay 11 event8221;.

The upper limit of the yield of the May 13 test was 30 ton if it was performed under conditions similar to May 11 explosions. If performed in a sand dune, the upper limit could be as large as 300 ton. According to Indian officials, yield from May 13 tests was about 800 ton.

The US scientists said, a blast larger than 30 ton would have been detected by their stations but one ten times larger could have escaped detection if detonated in sand, as reported.

The results are based on analysis of signals recorded at two seismological stations near India and Pakistan, that are part of a global network of 321 stations to record even small underground nuclear tests.

The new estimate for the May 11 blasts has been calculated by a team of 19 academic and US government seismologists.

Accounting for errors associated with 8220;emplacement conditions and near source effects8221;, and scaling the analysis to the background noise levels at the stations, the scientists have estimated that the upper limit ofthe May 13 test by India is only 30 ton, if it was performed under conditions performed under conditions similar to May 11 tests.