The yields of the Indian nuclear tests of 1998 and their relevance to TestBan verification

Indian scientists estimate the yield of the II May 1998 nuclear test at Pok hran as around 60 kt, Some of the assumptions made in making this estimate appear unjustified: for example, the assumption that interference between P waves from the two largest explosions in the test reduces the observed bod y-wave nnagnitude and that the NEIS estimate of surface wave magnitude is r eliable. We show from a comparison of P amplitude observations at twelve co mmon stations for the 11 May 1998 and Is May 1974 tests that the maximum yi eld of the 1998 test is around 40 kt with the assumption that the yield of the 1974 test is 13 lit. However, one Indian estimate of the yield of the 1 974 test is 8 lit, implying that the 1998 test has a maximum yield of aroun d 25 kt, Our estimate of yield from surface waves is 15-20 lit, The evidenc e is then that the yield of the 1998 test is closer to 20 lit than the 60 l it obtained by Indian scientists. Even assuming however that the Indian yie ld estimate is correct the capacity of the International Monitoring System being set up to verify the Comprehensive Test Ban, should be sufficient for the System to act as a strong deterrent to any nation on the Indian Stab-c ontinent and adjacent areas attempting to carry out a clandestine test.