Determining Shallow Earth Structure

This activity is intended to extend students' learning of fundamental physics concepts (e.g. reflection, refraction and transmission of energy) through a real-world application. 

Energy from an explosion travels through the Earth as seismic waves. Like other waves, seismic waves obey the laws of physics. For example, seismic waves have difficulty passing from one medium into another, hence they reflect (partially) from such a boundary. Waves also have different speeds in different media because each medium has its own rigidity. Different speeds in different rock layers give rise to refraction effects, including critical angle. Using basic physic principles and geometry students examine seismic data to calculate the seismic wave velocities in several rock layers and then use this information to determine the depth to the boundaries, and estimate what rock type makes up each layer.


Students will be able to:

  • Identify the following elements of a seismic experiment:Angle of reflection, Angle of refraction, Headwave, Direct wave, Normal, Critical angle, Snell’s Law
  • Determine the depth of bedrock by analyzing a simple seismic section. 

Total Time: 1h 30min
Level: Intermediate

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