11.   But for decades such detectors have also been used for monitoring arms control treaties and nuclear blasts, whose characteristic signatures in most cases are easy to distinguish.

12.   By late afternoon, the evacuated area around the World Trade Center looked like the site of a nuclear blast.

13.   Civilian scientists are strongly criticizing the federal government for saying that a seismic event that rocked the Russian wilds two months ago might have been an underground nuclear blast.

14.   During civil defense classes we were told to cover ourselves with something white, preferably a sheet, in the event of a nuclear blast.

15.   Even today, experts warn, it may not be easy to distinguish secret nuclear blasts from false alarms such as small earthquakes, mine explosions, exploding meteors.

16.   Federal scientists recently suggested that a repository there might blow up in a nuclear blast.

17.   Ever a number cruncher, he made detailed calculations of how well sensors in deep rocks might detect faint rumbles from distant nuclear blasts hidden beneath the earth.

18.   From the beginning, the Clinton administration has acknowledged that the CIA is not sure if it can distinguish extremely low yield nuclear blasts from conventional explosions or earthquakes.

19.   Hard to believe, but schoolchildren were once taught that they could survive a nuclear blast by perfecting their duck-and-cover technique.

20.   He discovered a way of predicting how the shock wave from a nuclear blast would spread out.