Leet Tells Scientists Nuclear Test Blasts Can Be Detected

L. Don Leet, professor of Geology chose the May 9th meeting of the American Academy of Sciences to outline his plan for seismic detection of underground nuclear tests. At the meeting in Brookline, Leet showed slides to the assembled scientists illustrating his contention that earthquake and blast waves are visibly different when recorded from a sufficient distance.

The distance at which graphic differences become apparent, Leet feels, has been overlooked by scientists who are engaged in detection research for the U.S. government. Because these scientists, who worked on the Berkner Panel and the Air Force's Project Vela Uniform, reasoned that moving their stations closer to the suspicious seismic events would enhance chances of detection, Leet feels "they have missed the forest for the trees."

Disturbances in the earth's crust generate primary and Secondary (P and S) waves which pass through the crust, as well as Long (L) waves, which travel around the surface of the earth. If these waves are generated by an earthquake, Leet tried to show through his slides, the P waves die first. But if they are generated by a blast, stations located sufficiently far from the event will record P waves long after the others have faded.

Many debates on the advisability of nuclear test bans have centered around the question of detection. Critics of such bans have often claimed that without a rigid inspection system an agreement on testing would be worthless since there would be no way to tell if a country was trying out new weapons surreptitiously.

Leet, who has been in charge of the University's seismographic section since 1931, feels that a thorough knowledge of blast records is a prerequisite for anyone studying detection possibilities. He will restate the theory expounded Wednesday night in the June issue of Scientific American, and here, in a forum on inspection scheduled for May 24.