Saturday, January 29, 2011

The Leet seismograph, named after L. Don Leet

The Leet seismograph is named after its developer, the geoscientist Dr. L. Don Leet, who has been chairman of the Division of Geological Sciences at Harvard University, Director of the Harvard Seismographic Station [1] and was a co-founder of the Vibration Engineering Company, where he developed the first three-component portable seismograph in the 1940s [2,3].

In his earthquake-seismology book, which Don Leet wrote together with his wife Florence [1], he describes how he was lured down from Boston to New Mexico in 1945 to record seismic waves from explosion tests. It turned out that those testing experiments involved nothing less than atomic bomb explosions: “Among the seismographs recording this event were four portable Leet seismographs, one operating by remote control five miles from the bomb. The largest motion registered on it was produced by a type of surface earth wave (the ‘hydrodynamic’) that had not previously been recognized. Another type of earth wave also was recorded on this same record. Its vibration had a particle motion (‘coupled’) that I had first recognized and reported in 1939, when it had been recorded from dynamite blasts. These two surface waves have since been identified on records from dynamite blasts and from nuclear blasts, but not on records from earthquakes.”

When the relationship between the United States and the Soviet Union began to get shaky, recording of underground earth waves became a matter of international security and headline news and speculations about seismic events spread around the globe almost as fast as their recordable waves.

Keywords: history of seismology, atomic bombs, nuclear explosion, artificial earthquakes

[1] L. Don and Florence Leet: EarthquakeDiscoveries in Seismology. Dell Publishing Co., Inc, 750 Third Avenue, New York, N. Y. , 10017, USA, 1964; pages 178 and 181.
[2] GeoSonics Vibra-Tech: History [].
[3] History of Explosives and Blasting, see entry for 1950: first portable 3 component monitor developed, the Leet Seismograph weighs 65 lbs [].

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