How to Build a Simple Seismograph with Your Kids

Learn to build a working seismograph at home using common materials to detect earthquakes and vibrations with your children.

  1. What You'll Need. Gather these common household items: a cardboard box (shoebox size works well), a plastic cup, string or yarn, scissors, tape, a marker or pen, white paper, modeling clay or play dough, and a small weight like a fishing sinker or heavy washer. You'll also want a table or sturdy surface near a wall where you can set up your seismograph.
  2. Prepare Your Base. Turn your cardboard box upside down so the opening faces the ground. This creates a stable platform for your seismograph. Cut a small hole in the top of the box, just big enough for your string to pass through. The hole should be positioned so that when you hang your cup, it will dangle in the center of the box's top surface.
  3. Create the Pendulum. Take your plastic cup and poke a small hole near the rim. Thread your string through this hole and tie it securely. The string should be long enough that when hung through the box, the cup hangs about an inch above the box's surface. Place your weight (like the washer) inside the cup to make it heavier and more stable.
  4. Add the Recording System. Tape the marker or pen to the bottom of the cup, pointing downward. The tip should just barely touch the surface when the cup hangs freely. Place a long strip of white paper on top of the box, positioned so the pen tip can draw on it. You can tape the paper down, but leave it loose enough that you can slowly pull it sideways later.
  5. Set Up and Test. Place your seismograph on a sturdy table against a wall where it won't be bumped accidentally. Thread the string through the hole and adjust the height so the pen just touches the paper. Test your seismograph by gently tapping the table or having someone walk heavily nearby. The pen should move and make marks on the paper as the base vibrates but the weighted cup stays relatively still due to inertia.
  6. Using Your Seismograph. To record 'earthquake' activity, slowly and steadily pull the paper strip sideways while vibrations occur. The pen will draw a wavy line showing the intensity of ground movement. Try different tests: have family members jump, close doors firmly, or even check if you can detect a washing machine running. Compare the different wave patterns you create.