Chapter 12. Earthquakes


Learning Objectives

After carefully reading this chapter, completing the exercises within it, and answering the questions at the end, you should be able to:

  • Explain how the principle of elastic deformation applies to earthquakes
  • Describe how the main shock and the immediate aftershocks define the rupture surface of an earthquake, and explain how stress transfer is related to aftershocks
  • Explain the process of episodic tremor and slip
  • Describe the relationship between earthquakes and plate tectonics, including where we should expect earthquakes to happen at different types of plate boundaries, and at what depths
  • Distinguish between earthquake magnitude and intensity, and explain some of the ways of estimating magnitude
  • Explain the importance of collecting intensity data following an earthquake
  • Describe how earthquakes lead to the destruction of buildings and other infrastructure, fires, slope failures, liquefaction, and tsunami
  • Discuss the value of earthquake predictions, and describe some of the steps that governments and individuals can take to minimize the impacts of large earthquakes

Why Study Earthquakes?

Earthquakes, like volcanoes, are fascinating partly because they are so scary.  That’s not surprising because time and time again earthquakes have caused massive damage and many, many casualties. Anyone who has lived through an  earthquake[1] will not easily forget the experience (Figure 12.1). But geoscientists and engineers are getting better at understanding earthquakes, minimizing the amount of damage they cause, and reducing the number of people affected. They are also making progress in communicating to both individuals and governments the need to be prepared. There is no getting around earthquakes being scary, but knowing what to expect, and being confident in one’s ability to make the best of a challenging situation, go a long way toward helping.

A schoolroom in Courtenay damaged by the 1946 Vancouver Island earthquake. If the earthquake had not happened on a Sunday, the casualties would have been much greater. [from Earthquakes Canada,]

Figure 12.1 A schoolroom in Courtenay BC damaged by the 1946 Vancouver Island earthquake (magnitude 7.3). If the earthquake had not happened on a Sunday, the casualties would have been much greater. [from Earthquakes Canada,]

  1. Read more about important earthquakes in Canadian history here: