Living in Earthquake Country (6-12)
Overview of the box
Concepts and Standards
Lessons:
1 Earthquake damage
2 Faults are at fault:
Where earthquakes occur
3 Earthquake patterns
Activities:
1 Patterns from Parkfield
2 Patterns of recurrence
3 Recurrence on the
Hayward Fault
4 Seismic waves
5 A whole lot of shakin’
goin’ on!
6 Landslides, liquefaction,
and structural failure
7 Examining all the factors
Online resources
Student Web Page

Extras:
Lessons that use the
Rapid Earthquake Viewer
Teaching Boxes Home
Lesson 3: Earthquake Patterns

Activity 3

Recurrence on the Hayward Fault

Materials / Preparation

Grouping

Individual

Teacher tips

This lesson is identical in concept to Exercise 2 of the previous activity, but it uses a data set from the Hayward fault in northern California. You can select one that is more geographically relevant, however, we recommend that you try to have students do both examples to reinforce the concept of using recurrence intervals to estimate earthquake hazard. This also allows for a fruitful comparison of the three datasets as a culminating assessment for the lesson. We have provided an Answer Sheet to the Hayward Recurrence Student Worksheet.

Procedures

  1. Conduct a class discussion on what the students discovered from the previous activity. What did the activity show about cyclical patterns of earthquake occurrence on the San Andreas? Are the patterns for the Parkfield segment of the San Andreas fault the same as for the Mojave segment? (Answer: There were different recurrence intervals of 22 v. 50-250 years and Magnitude 6 v. Magnitude 8 earthquakes) Can you make a hypothesis about the relationship between the relative length of the fault and the relative recurrence interval?
  2. Explain to students that they are going to take a look at the data from a third fault to test their hypotheses. Hand out copies of the Hayward Recurrence Student Worksheet and have students work either individually or in pairs to complete the activity.
  3. Ask students if the graph indicates that there is a cyclic pattern to the Hayward fault. According to this information when will or should there have been, an earthquake on the Hayward fault?
  4. Have students rank Parkfield, the Hayward fault, and the San Andreas in the Mojave in terms of how likely each is to experience an earthquake within the next 25 years.
    Teacher tip: Students should consider both the time since the last earthquake and the typical time between earthquakes. Parkfield is clearly most likely to have an earthquake in the next 25 years, then Hayward, then the Mojave. Parkfield had an earthquake very recently (2004), so it has not had much time to re-accumulate strain. For that reason, Parkfield is less likely to have a very large earthquake in the next 5 or 10 years. However, in the past, it has taken an average of only 22 years to re-accumulate enough strain to have an earthquake. Hayward has large earthquakes about every 170 years; the most recent occurred in 1868. Mojave has large earthquakes about every 200 years; the most recent occurred in 1857.

    Be sure to remind students that even though Parkfield has earthquakes more often, they are much smaller. (Parkfield = Magnitude 6; Hayward = Magnitude 7; Mojave = Magnitude 8+). The idea that smaller earthquakes cause less damage each time, but occur more often will be reinforced in Lesson 5 and be an important concept in the culminating activity (Lesson 7).

Resources used

None

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