1. Build Your Own Seismograph
Students will gain a greater appreciation of how a seismograph works, and a better understanding of recordings of ground motion that they see on seismograms.
In small groups of 3-4 students, students are asked to design and construct a seismograph using common household and craft materials provided. Students will demonstrate to the class how their seismographs record motion.
Begin with a demonstration in which the students jump up and down at various distances from the school seismograph, and then look at the resulting seismogram on the screen. This will give them a feel for how sensitive their seismograph is, and what these non-quake (noise) disturbances look like on a seismogram. Cover the seismograph so that the students don’t see it’s inner workings before they do the lab. We want them to think through this Build Your Own Seismograph exercise from first principles, without being too biased by what the mechanism of the seismograph looks like. Try jumping very near the seismograph and then jumping the same amount progressively farther away from it to see how the resulting signals compare on the screen (and how the amplitudes of the signals decay with distance). Also, try one student, then two students, then more students jumping, etc. to see how much bigger the signal is on the screen as more students jump.
Next ask the students to think of a creative way to make an instrument that measures seismic waves generated by an earthquake using some of the materials provided. Ask them to draw a clear diagram of their seismograph, and label all the parts. For homework, ask them describe how their seismograph works.
A good design would be:
- capable of determining the relative size of each disturbance it measures;
- capable of measuring vibrations continuously for at least few sec;
- capable of measuring vibrations from three different sources: a bang on or shaking of the table holding the seismograph; a person jumping up and down on the floor next to the table on which the seismograph is located; and a ball bounced off of a wall or floor nearby.
After the designing and building of the seismographs have been completed, each team should present to the class how their seismograph works. After each group presents their design, the teacher will give a brief description of how seismographs (including their school seismograph) record ground motion.
How can your seismograph design be improved?
What elements of your seismograph are similar to seismographs used by seismologists? What elements are different?
What were some of the challenges you encountered in designing and building your seismograph? How did you try to solve those problems? Did you succeed in solving those problems?
What are the physical principles underlying the mechanism of how your seismograph measures ground motion?
Can you think of any other reflection questions that would be appropriate for this exercise? If yes, what is your question, and how would you answer it?
Suggested list of materials for this exercise:
- masking tape and/or duct tape
- weights or sinkers
- empty paper towel rolls or toilet paper rolls
- coil springs
- paper plates
- paper cups
- pipe cleaners
- pens and pencils
- bouncy ball for demos
- string or wire
- miscellaneous items brought to class by the students.