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 2

Patterns of Recurrence

Materials / Preparation

  • Reproduce the San Andreas fault rupture Graphing Template worksheet for use as an overhead
  • Student materials:
    • Recurrence Interval Activity 9
    • the San Andreas fault rupture Graphing Template
    • (optional) graph paper and colored pencils
    • scratch paper and/or a calculator for making calculations

Grouping

Group and/or individual assignment

Teacher tips

Answers to the worksheet can be found on the Answer Key. Scroll down to Activity #9. Also, see a Finished Example using the graphing template . We recommend that the students work off-line on this activity. You may want to go through the directions on the graphing activity with the students and illustrate how to graph the information.

Procedures

  1. Review what the students learned from the Parkfield activity in the previous lesson. What did we learn about recurring patterns of earthquakes along the Parkfield fault? One thing that is certain, earthquakes do occur along faults where plate motion causes periodically repeating earthquakes. Each earthquake causes a little bit of motion, and over long periods of time, these little amounts start adding up so that plates can move great distances.
  2. Introduce students to the vocabulary words:
    a. recurrence interval = the average time between earthquakes on the same fault
    b. slip = amount of relative motion along a fault, like the distance between two offset fences in a single earthquake (picture of evidence of slip), or the total relative offset of two plates over millions of years
    c. slip rate = the speed the fault is moving on average, usually measured in centimeters per year. Note that most faults only move during earthquakes where there might be several meters of movement in a few seconds followed by decades when the fault does not move. Hence, the idea of an average rate.
  3. Hand out the Recurrence Interval activity. Start out with students working in pairs on Exercise 1 from the activity. Here they will relate the amount of slip in a single earthquake to the total accumulated offset over a very long time.
  4. Hand out the graphing template and start Exercise 2 of the activity as a whole class. Exercise 1 showed that a lot of earthquakes had to happen to cause the total amount of offset of two plates along a fault. Exercise 2 focuses in on how often those earthquakes occurred.
    a. On the board or overhead projector, model how to plot the data. Have students finish on their own, or working in pairs.
    b. Exercise 3 of the web activity can be completed for homework. It relates the amount of slip in individual earthquakes, the average slip rate of the fault, and the recurrence interval for earthquakes on that fault.

Resources used

Graphing Template
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-104

Finished Example using the graphing template
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-105

Picture of evidence of slip
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-107

Recurrence Interval
http://www.teachingboxes.org/catalog.jsp?id=DLESE-000-000-008-831

Answer Key
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-106

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