Seismograph Lesson for Kids: Definition & Uses

Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Get ready for some Earth shaking learning! In this lesson, you'll learn what a seismograph is and how scientists use a seismograph to learn things about earthquakes.

What Is a Seismograph?

Did you ever throw a pebble in the water and watch as small waves spread out from where the pebble landed? When an earthquake hits, it sends out waves as well. Waves from an earthquake are called seismic waves. Unlike waves in the water, seismic waves travel through the ground, causing the Earth to shake.

Scientists can measure and record the seismic waves made by an earthquake using an instrument called a seismograph (pronounced siz-muh-graf).

A seismograph measures how much the Earth shakes

The word seismograph is the combination of two words. Seismos is a Greek word that means 'shaking,' and a graph is a way of recording something. So, 'seismograph' means a machine that records shaking.

The basic structure of a seismograph is pretty simple. A seismograph includes a base and a heavy weight hanging above it. The base has a rotating drum of paper, and the weight has a pen hanging down from it. When the Earth shakes, the base shakes too, but the hanging weight and pen do not. The pen makes marks on the paper that record the shaking. This paper record is called a seismogram.

Seismographs have been used for many years

What Is a Seismograph Used For?

A scientist can learn a lot of things about an earthquake by studying the markings on the seismogram. For example, they can tell how big the earthquake was. Did you ever hear of the Richter scale? It's a scale that scientists use to explain how strong an earthquake was. It's kind of like getting a grade in school, except instead of A, B, or C, the Richter scale uses numbers, like 5.0, 6.0, or 7.0.

Big wiggly lines on a seismogram mean the earthquake was big

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