Science
How does a seismograph work?
A seismograph works by keeping a heavy mass still while the ground shakes around it during an earthquake. The relative motion between the steady mass and the moving frame is recorded, tracing out the strength and timing of the seismic waves.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a seismograph works.
Step by step
- 1A heavy weight hangs so that inertia keeps it nearly still as the ground moves.
- 2The frame, anchored to the ground, shakes with the quake.
- 3Sensors record the motion between the still mass and the moving frame.
- 4Modern versions convert that motion into an electronic signal.
- 5The timing of different seismic waves reveals the quake's distance and size.
Frequently asked questions
- How does a seismograph measure an earthquake?
- A suspended mass stays still by inertia while the ground and frame move; recording that difference captures the ground's shaking.
- How do scientists locate an earthquake?
- Faster and slower seismic waves arrive at different times; comparing arrivals at several stations pinpoints the source.
- What's the difference between magnitude and intensity?
- Magnitude is the quake's energy at the source (one number); intensity is how strong the shaking felt at a given place.