Plate Tectonic - Hazards (4)
 Lab 

   
OBJECTIVES:
  • Comparing structural damage caused by earthquakes.
  • Designing structures that can withstand earthquakes.
VOCABULARY:
  • damage
  • disaster
  • intensity
  • magnitude
  • structural damage
MATERIALS:
  • toys
  • Shaker Boards (marbles, large plastic container lids, wooden boards)

Students build earthquake resistant structures.


Collapsed buildings, Peru

BACKGROUND:

It sometimes does not matter the intensity of the earthquake, but how the structures can withstand the force of the shaking. Sometimes landslides or tsunamiís caused by the energy destroys an area. Below are some examples of such disasters.

The southern Alaskan earthquake on March 27, 1964 had a 8.3 magnitude. It caused severe damage due to landslides and from a large tsunami wave that hit the area. Many homes and businesses were damaged because the structures could not withstand the mass movement.

A moderate earthquake (5.5) in Peru in 1962 caused complete damage to villages. The unreinforced adobe and wood structures could not withstand the shaking. The intensity of the earthquake was not great, but the damage was.

On June 16, 1984 a large earthquake was felt in the Nigata region in Japan. Large buildings collapsed due to the shaking. In some areas the ground was unstable and caused buildings to tumble. 

A 6.4 earthquake in San Fernando Valley region, just north of Los Angles, caused major damage to hospitals, homes, and freeways. After this earthquake, California created strict laws so builders would make earthquake resistant buildings.

In September, 1985, two large earthquakes (8.1 and 7.3) paralyzed Mexico City. Residents had no clean water for weeks. Large buildings collapsed, and people were trapped. Mexico did not use reinforced concrete structures, which could not take the intense shaking.


Hospital, San Fernando, California, 1971


Mexico City, 1985

 

In Sumatra-Andaman Islands there was a devastating  earthquake (9.0) on December 26, 2004.  It  occurred on the interface of the India and Burma plates and was caused by the release of stresses that develop as the India plate subducts beneath the  Burma plate.  At least 80,000 people were killed by the earthquake and tsunami in Indonesia. Tsunamis killed at least 41,000 people in Sri Lanka and10,000 in India. A total of over 150,000 people died mainly by a tsunami that hit the low lying areas along the rim of the Indian Ocean.

PROCEDURE:

  1. In this exercise, students experiment with structures. They design and build models composed of different types of materials on shaker tables, and then simulate earthquakes of various strengths to test their designs.
      
  2. If necessary, gather the materials to make shaker boards before lab. Boards should be about 12 x 18 inches (or longer than they are wide), with at least 3/4 inch thickness.
    1. Place the marbles in a plastic top that you might get in a coffee can. 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.
       
  3. 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.
     
  4. Using a different building block set at each station, have the students build an "earthquake proof" structure. Next, have them place different "real life" models in and outside their structures. Test the models using the four intensities and have students record their results.
      
  5. Have students discuss their results. Have them analyze why some students recorded different amounts of damage. They should realize that the building materials are an important factor. In addition, their structures lack foundations which in general will make them less stable than real buildings.
      
  6. You can extent this lab very easily by having the students redesign their structure to try and make it more resistant. You may want to go over more resistant shapes that the students learned in a previous lab. You may also want to describe the different types of reinforcement of structures.

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