Seismometer

A seismometer detects ground motion and records its variation over time. Its measurements reveal seismic waves from earthquakes, explosions, and other sources.

Inertial sensor: A device that measures motion or orientation using the behavior of a mass or other physical reference. Many seismometers infer ground movement from the motion of a suspended or spring-mounted mass.
Seismic wave: A wave of energy that travels through Earth or along its surface. Seismometers detect the ground motion carried by these waves.
Seismology: The scientific study of earthquakes, seismic waves, and Earth's internal structure. Seismometers provide the observations on which much of the field relies.
John Milne: A British geologist and engineer who helped develop modern seismology and the horizontal pendulum seismograph. His instruments helped establish systematic earthquake recording in the late nineteenth century.
Strong-motion seismograph: An instrument designed to record intense ground shaking without saturating or being damaged. It prioritizes large earthquake motions, unlike highly sensitive instruments optimized for weak signals.
Seismic mass: A mass inside a seismometer that responds to ground movement relative to the instrument frame. Its inertia provides the reference against which the instrument measures ground motion.
Seismogram: A recorded trace or digital time series of ground motion. It is the recorded output produced from a seismometer's measurements.
Earthquake early warning system: A system that detects an earthquake's seismic waves and issues alerts before stronger shaking arrives. Networks of seismometers supply the rapid detections used to generate warnings.
James Alfred Ewing: A Scottish physicist and engineer who studied earthquakes in Japan and designed sensitive seismographs. His work helped refine instruments for recording distant as well as local earthquakes.
Broadband seismometer: A seismometer designed to measure ground motion over a wide range of frequencies. Its broad frequency range contrasts with instruments tuned to a narrower band.

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