What does a seismogram show? Teachers' notes

Students identify some features of a real seismogram.

Learning objectives

Students will:

  • use information about predicted travel times of different phases of seismic waves to a given location
  • identify corresponding points on the seismogram for the arrival of the first P-wave and S-wave, and regions corresponding to surface waves.

Notes

This could be done as an individual or small group activity, or you may prefer to lead the whole class through it using a data projector.

For convenience, the activity is based on a copy of a screenshot and uses simplified information about predicted travel times. However, once students are familiar with the basic ideas, the activity could extended to be done with data downloaded from the internet or using data collected from your own school seismometer.

The most important things for students to note from the screenshot are that the waves arrive in the sequence P-waves, then S-waves, then surface waves (Love waves first, then Rayleigh waves).

Question 5 asks students to calculate the wavelength of seismic waves, given values for frequency and velocity. Students may initially be surprised to find that the wavelengths of surface waves are so much larger than those of other seismic waves. (From these values P-waves have average wavelength 32.5 km, S-waves 74 km, and surface waves 350 km!)

Resources needed

Each group will need: