Historical seismometers #3 - Ewing-Press

Welcome to the third post in my series on historical seismometers, featuring my favorite instruments from the Strasbourg Seismology Museum. After entries on the Wiechert and Galitzin seismometers, here is a post on the Ewing-Press.


Like the Galiztin, the Ewing/Press [photo credits Michel Dufloux] is an electromagnetic seismometer combined with a galvanometer. It's natural period is modifiable up to 30s. It is a long-period instrument, well adapted to recording surface waves, and was used in the first global seismic network, the WWSSN.

The instrument in our museum was made in 1953 at the Lamont Geological Observatory of Columbia. It was in use in Strasbourg from 1963 to 1975. My favorite feature is the glass ball on the vertical component (in the photo), which eliminates the effect of pressure variations on the seismic signal.

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