Press-Ewing seismograph

The Press-Ewing seismograph is a type of seismograph developed in the United States. It was designed for recording long-period seismic waves and was widely used globally. This instrument improved upon earlier designs, such as the Milne-type pendulum, by replacing the pivot with an elastic wire to reduce friction.1

A seismograph is an instrument that records seismic waves caused by events like earthquakes, explosions, or other ground-shaking phenomena. These instruments use electromagnetic sensors to convert ground motion into electrical signals, which are then processed and recorded. While "seismometer" and "seismograph" are often used interchangeably, a seismograph specifically has the capability to record these phenomena, producing a record called a seismogram. Seismographs have applications beyond locating earthquakes, including petroleum exploration and monitoring volcanic activity.1