An instrument that measures and records the motion of the ground during earthquakes and other seismic events. It produces a visual record called a seismogram showing the intensity and duration of ground movement.
From Greek seismos (earthquake, shaking) + graphein (to write), literally meaning 'earthquake writer.' The term entered English in the 1850s as scientists developed instruments to record seismic activity. The compound follows the Greek pattern of combining descriptive prefixes with -graph to indicate recording instruments.
A seismograph is literally an 'earthquake writer' — it writes the story of the Earth's movements! This connects beautifully to other -graph instruments like telegraph (distant writing) and phonograph (sound writing). All these devices transform invisible forces — earthquakes, electricity, sound waves — into visible written records we can study.
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