The first study on yields was by Dr Terry C Wallace of the University of Arizona from a place in Tibet that was almost equidistant from Pokhran and Chagai Hills. The study measured a seismic body magnitude (MB) of 5.4 for the Indian nuclear explosion and 4.5 for the Pakistani test. When this data is converted in terms of yield, it gives a ratio of 13.

Releasing the details of the study to The Indian Express, Dr Janardhan Negi, emeritus scientist at the National Geophysical Research Institute (NGRI) here said there is a ``tremendous amount of controversy among seismologists internationally regarding yield estimates of the two blasts. The new study would put all this to rest.''

Earlier, CTBT officials had estimated the yield of Indian testaround 20-30 kilotons and the yield for Pakistan's test 5 kt. India had claimed an yield of 60 kt and the corresponding Pakistani explosion would be or 5 kt approximately.

``However, the generally accepted 8 kilo tons estimate for Pakistani explosion will increase the estimate for Indian explosion to 100 kilo tons. The later estimates sound quite reasonable for a thermo-nuclear device, more particularly when its seismic punch is muffled in the old cavity formed by Pokharan-1 explosion of 1974'', Dr Negi said.

Another study made by German Experimental Seismic System directly compared the seismograms of May 11 and May 28 explosions also showed that the Indian yield was certainly much larger.

``Interestingly, the seismic wave form analysis shows homogeneous rock formations at Pokhran and possibly a neat simultaneous third generation type nuclear explosion on May 11. The corresponding wave form of Pakistani explosions is quite complex. This might be due to testing of a first generation nuclear device andheterogeneous fault mosaic of Chaman fault system at Chagai'', Negi added.