Sensitive Seismographs

As atomic explosions go, the recent Gnome test in New Mexico (TIME, Dec. 22) was relatively feeble. It generated only five kilotons of energy. But last week Chief Seismologist Leonard M. Murphy of the Coast and Geodetic Survey announced that Gnome's earth waves were recorded by seismographs near Tokyo, 6,000 miles away. Uppsala, Sweden (5,200 miles), Sodankyla, Finland (5,000 miles), and Fairbanks, Alaska (3,000 miles) also detected the explosion, and all the stations recorded the "first motion," the outward push that is characteristic of bomb waves and can distinguish them from natural earthquake waves.

The seismologists were well prepared; they had been told the instant when Gnome would explode. Still, the detection of so small a bomb at so great a distance without special instruments will surely revive the controversy between scientists who believe that clandestine underground tests can be detected and those who think that there is no use trying.

Scientists will now re-examine the argument that a practical system can be developed for monitoring a test ban. As they check on future tests, the scientists will be helped by a network of ultrasensitive seismographs that the U.S. Coast and Geodetic Survey has begun to install in 65 countries strung around the globe. Officially, those seismographs are there to record the world's earthquakes, but there is no way to keep them from detecting bomb waves also.

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