Plate Tectonic - Hazards (6)

  • Exploring damage created by earthquakes.
  • Designing structures that can withstand different earthquake intensities.
  • Modified Mercalli Scale
  • Richter Scale
  • worksheet
  • Shaker Tables
  • small building toys

Students build earthquake resistant structures.

Building collapse triggered by seismic waves


Different types of building materials respond differently to the shaking caused by seismic waves. Materials such as brick and stone break easily during an earthquake. The mortar that typically holds these materials together shakes loose because it is not strong. Brick, stone, and mortar structures are very unsuitable dwellings for "earthquake country." In addition, non-bearing walls of bricks or stone are extremely dangerous because they are not structurally part of a house. Wood and steel are much better at withstanding seismic waves. Both of these materials flex as the earth shakes.

Weak materials can be reinforced to make them relatively safe. Reinforcing structures with a steel frame, or driving beams through a structure will help support it during shaking.

Architects and engineers can also design and construct buildings that can withstand intense ground shaking. For example, designs that are broader at the base than at the top or homes that are not more than two stories high survive earthquakes fairly well. Ornate pillars or facades (fake fronts) on a home do not survive shaking well. Engineers need to consider the rigidity of the building material. The material should be able to bend or flex without damage in an earthquake. For instance, wood bends but brick and mortar does not. Engineers need to reinforce brick masonry by putting steel beams through the structures. Many buildings were built prior to strict earthquake codes, so in many places such reinforcement is necessary. Bracing a structure is an alternative way to prevent damage. Engineers and architects can make structures earthquake resistant, but they cannot make them earthquake proof. If you are unfamiliar with reinforcing techniques or want to learn more, the Association of Bay Area Governments website has excellent, up-to-date information (

  1. If necessary, gather the materials to make shaker boards before lab. You require a flat board about 3/4 inch thick with a length longer than its width (12 x 18 inches). Here are directions for assembling them:
    1. Place the marbles in the plastic top. The marbles will act as ball-bearings in the experiment.
    2. Balance the shaker board on top of the marbles. This completes the shaker table.
  2. Set up stations with shaker tables and building materials. Toys can include Lincoln Logs, Legos, Slinky building toys, or any other building toys that students can bring in from home.
  3. Discuss with students that the hazards of an earthquake are directly related to the magnitude of seismic waves. Have the class make a list of earthquake damage on the board. It should include such school and home damage as unreinforced masonry, bookshelves that are not secured, or houses that are not bolted to their foundations. Explain that some hazards can be avoided by taking precautions before an earthquake occurs.
  4. Show the class the images of building damage caused by earthquakes from the Earthquake Slideshows.
  5. Demonstrate how the shaker board works to the class. When it is "jolted, "it simulates the movement of the Earth's surface (an earthquake). The "earthquake" creates energy that moves along the surface of the shaker table as waves. Control the intensity by how fast you shake the board. Demonstrate to students that a strong earthquake occurs when you shake quickly; a weak earthquake occurs when you shake it less violently. A moderate earthquake occurs when you shake it somewhere in between. On the lab worksheet, slow-long means to move the board in the long direction slowly (this is relative). Quick-long refers means moving the board in the long direction quickly. This will illustrate that intensities B and D (both quick) represent a high number on the Richter Scale while A and C represent a low Richter number.
  6. Have the students complete the lab, following the worksheet. Emphasize trying to improve their building structures to prevent damage.

    You may want them to design a structure and shake it once, before you discuss how you can reinforce the structure. If you talk about it before they build the first structure their structures will tend to have those features that you discuss already in them. The objective of this lesson is for them to see that a dramatic change in the strength of a structure that they have reinforced. You make want to have double stick velcro available, so students can secure their foundations to the shaker board. This exercise has become to known as "Save the Baby."

  7. Discuss different real building materials and their relative resistance to earthquakes. The students should be aware that most structures have foundations, unlike the models they are using. You may want to highlight the structures that were the most resistant.

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