Show your students how scientists collect earthquake data and give them the opportunity to collect their own scientific data! This old-school video by PBS Learning Media shows you how to make your own homemade seismometer that demonstrates the concept behind the scientific instrument and how it collects earthquake data.

Background

Seismometers are scientific instruments that collect data on earthquakes, volcanic eruptions, and explosions. These instruments are important tools used to measure and locate these geologic events as well as create a map of internal structures in the earth. The seismometer works by measuring movements in the ground and can detect the smallest of ground movements. While there are many different kinds of seismometers, they all function with the same basic principle.

A supporting structure is anchored to the ground and supports a free mass that is used to measure the intensity of an earthquake or other seismic event. The intensity of the seismic event is recorded either on paper or electronically. Generally, a seismometer can only measure waves from a single direction, so multiple instruments are needed in order to record waves from more than one direction.

There are four main types of waves recorded on a seismometer. Two of these body waves (P and S waves) travel deeper in the earth, and the other two travel at the surface (L waves). The P (primary) wave is the first to be recorded on a seismograph and can travel at 6 kilometers per second. The S (secondary) wave is similar to the P wave in its pattern but follows after it. In order to locate an earthquake, scientists can calculate the time interval between P and S wave arrivals on the seismograph stations.

What You’ll Need

In order to construct your own homemade seismometer, you’ll need the following items:

1. cardboard box (with flaps cut off)
2. plastic cup
3. string
4. felt tip marker
5. small rocks
6. clay
7. paper
8. scissors

How to Make the Seismometer

If you need a visual guide to make the seismometer, check out this video by PBS Learning Media. Here are the steps to take to construct it:

1. Cut the flaps off the cardboard box so that one side is open
2. Take a pair of scissors and cut two small holes in the center of one side. The two holes should be about an inch apart from one another
3. Poke a hole in the bottom of a plastic cup, and poke two holes at the rim of the cup so they line up with one another
4. Take the felt tip marker and put it through the hole in the bottom of the cup, with the tip of the marker facing out of the cup
5. Wrap the clay around the marker to keep it in place inside the cup. Clay can be substituted with tape.
6. Thread a piece of string through the holes near the rim of the cup.
7. Take the two ends of the string and place them through the hole in the cardboard box. The cup will hang suspended inside the box.
8. Hang the cup so that the tip of the marker just touches the bottom of the box. When a desired length is found, tie off the string at the top of the box.
9. Fill the cup 3/4 full of rocks to weigh it down. Other similarly sized objects can be substituted (marbles, bolts, spare change, etc)
10. Place a sheet of paper underneath the marker. Lift the marker to prevent any marks being made until you are ready to test.
11. To test the seismometer, tap or gently shake the box while slowly pulling the sheet of paper out of the box.
12. Experiment with different kinds of movements to measure on the sheet of paper.

Connecting Concepts (NGSS)

• Analyze and interpret data on natural hazards to forecast future catastrophic events and inform the development of technologies to mitigate their effects.

Disciplinary Core Ideas

ESS3.B: Natural Hazards

• Mapping the history of natural hazards in a region, combined with an understanding of related geologic forces can help forecast the locations and likelihoods of future events.

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