Fairly simple to make, a little difficult to explain! It's a bit of a crude model, but it does give your students an idea of how seismographs work.
Empty cereal box.
Paper tape (for a calculator)
Small paper cup
Pennies (other other material for weight)
How To Assemble:
Cut out most of the large sides. Leave about an inch border on the right, left, and top. Leave about two inches (or more) on the bottom.
Cut a slit in the bottom border, on each side of the box, wide enough for paper tape to pass through.
Punch a hole in the top border on each side.
Punch a hole on each side of a small cup.
Cut a small x in the bottom of the cup.
Poke a pen through the bottom of the cup (a felt tip works best).
Use string to suspend the cup from the box.
Add some pennies to the cup for weight. (You could also use rice or dried beans, but they create a much larger mess if spilled!)
Thread the paper tape through the slits.
Adjust the pen so that it writes on the paper.
Set the seismograph on the table. Have one person gently shake the table, to simulate an earthquake. While the quake is going on, have another person slowly pull the paper tape through the seismograph.