Have the students move into groups of 10-15 in an area where they can stand shoulder to shoulder in a line with their arms across each-other's shoulders. To simulate a P-wave, push the group from one end of the line. All the students will bend, but straighten. For an S-wave, have the person at the end of the line bend at the waist to almost a 90-degree angle and then to stand up straight again. This will force the next person, and then the next person, and so on to do the same. Students in other groups can measure the time it takes for a wave to propagate.
ISSN 1089-9995
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Journal of Geoscience Education website