geology lab materils (3)

Earthquake Hazards Inquiry | Activity 11.1 Name: Course/Section: Date: Lea rning GOAL You will experiment with simple models to develop your intuition about how earthquake damage to buildings might be related to the physical properties of the Earth materials on which they are constructed. You will then apply your insights to evaluate earthquake hazards and human risks in San Francisco. A Obtain a small plastic or paper cup. Fill it 1 /4 full of water. Then without moving the cup, slowly sprinkle quartz sand grains into the cup, allowing the grains to sink to the bottom of the cup. Keep adding sand a little at a time just until the sand gets to the top of the water. Place two or three coins upright in the sand so they resemble vertical walls. The coins are meant to represent buildings constructed on a substrate of uncompacted sand. This is model 1. 1. Simulate an earthquake by tapping the cup on a tabletop while you rotate the cup counterclockwise. Describe what happened to the vertical coins in the uncompacted sediment of model 1 when you simulated an earthquake. 2. Now make model 2. Remove the coins from model 1 and press down on the sediment in the cup so that it is well compacted. You might need to drain some of the water from the cup because you want the flat upper surface of the sand to be above the water level in the cup. Then place the coins into this compacted sediment just as you placed them in model 1 earlier. Simulate an earthquake as you did for model 1. What happened to the vertical coins in the compacted sediment of model 2 when you simulated an earthquake? 3. Based on your experimental models 1 and 2, which kind of Earth material is more hazardous to build on in earthquake-prone regions: compacted sediment or uncompacted sediment? (Justify your answer by citing evidence from your experimental models.) 4. Consider the moist, compacted sediment in model 2. Do you think this material would become more hazardous or less hazardous to build on if it became totally saturated with water during a rainy season? To find out, design and conduct another experimental model of your own. Call it model 3, describe what you did, and explain what you learned. B REFLECT & DISCUSS Write a statement about whether wet compacted sand is stronger, weaker, or about the same strength as wet uncompacted sand and what the reason for this might be. 299