Earthquakes by Claire and Nisha
We're Claire and Nisha, and we live in a place where earthquakes are NOT science fiction! We live in San Francisco, where you can really feel the earth move under your feet. The last big quake here was in 1989, before we were born. We wondered if we could learn about how the earth moves in an earthquake by looking around the city. Our question: How does the earth move when there's an earthquake?
What did we do?
We visited the Lawrence Hall of Science to learn about how earthquakes happen. We saw that the San Francisco area sits right on top of the boundary between two "plates" below the surface of the ground. We found an earthquake simulation we could stand on, that shows how the plates either move up and down, or move past each other. As we went around town, we looked for cracks in the streets, buildings, or ground that resembled these models.
What did we find out?
We found lots of evidence of earthquake activity where the ground moved past each other. The curbs in the neighborhoods near Berkeley had shifted by as much as 18 inches! And at Berkeley Stadium, the walls of the stadium have cracked, and the two pieces have shifted by 6 inches or more. Some of these shifts have happened slowly over the years. This is called "fault creep". Other times, the shift happens all at once, and that's when there's a serious earthquake.
- Make your own earthquake detector, or "seismograph". Go to http://cse.ssl.berkeley.edu/lessons/indiv/davis/hs/Seismograph.html to see how. Use it to detect tremors in your house, such as when you jump on the floor. Can your seismograph detect your feet stomping? Take the seismograph outside, too, and see if you can make the ground vibrate enough by jumping to make the seismograph pen wiggle around.
- Build a model town on a platform out of blocks, cardboard, clay or other materials, and simulate an earthquake by slowly sliding the model platform back and forth a few times. Which parts of the model survive the earthquake? Make different sizes and shapes of "buildings" to see which are the most durable in an earthquake.
- Use this earth science investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!