Press-Ewing Seismograph on Jeopardy!
An important piece of earthquake-science history popped up a few weeks ago on Jeopardy: “The Press-Ewing was an early seismograph, recording waves from these events.
If you didn’t know a Press-Ewing from a French press, you were in luck. For $200, all you needed to know to formulate the question is what a seismograph measures.
What is an Earthquake?
But what is a Press-Ewing, and why was it important? It never became a household name, but in 1959, it did appear on the cover of Scientific American in a cheerful watercolor rendering. Today, the instrument is held in collections at Cornell University, Strasbourg University in France and at Columbia University’s Lamont-Doherty Earth Observatory, the campus where it originated.
Frank Press designed the instrument in the late 1940s while he was a Lamont graduate student under Lamont’s founding director, Maurice “Doc” Ewing. It became the first mass-produced seismograph to accurately record an earthquake’s so-called “long-period,” or slow-moving, energy waves rippling across earth’s surface. Most seismographs until that time were best at measuring high-frequency body waves rocketing through earth’s interior.
Surface wave recordings by the Press-Ewing helped confirm that oceanic crust was uniformly thin, three to four miles in depth, compared to continental crust, which could be up to 25 miles thick. “The ‘inside’ of the earth is closer to the surface than we had thought,” wrote Lamont seismologist Jack Oliver, in his 1959 Scientific American cover story, Long Earthquake Waves. Why oceanic crust was thinner would become apparent with the later discovery of mid-ocean spreading ridges, where earth’s plates were tearing apart at the seams, generating new crust.