AY Honors/Geology - Advanced/Answer Key

2. Provide the following information:

a. How do earthquakes tell us what the interior of the earth is like?

Answer: For one, they show us that faults are active and moving. Faults are rock fractures that show evidence of movement. Earthquakes generally happen along faults. Rocks move apart releasing energy that causes an earthquake. The energy released causes waves (seismic). In fact the core of the earth was discovered with seismic waves. They bend along the interfaces of different materials. There are two different waves. P waves travel through fluid and solids. S waves do not. They only pass through solids. By noticing that the S waves did not go to the center of the earth they came to the conclusion that it must be a fluid, for S waves cannot pass through fluids. P waves bend in the core because they are slowly passing through a liquid. This has also helped them estimate the size of earth’s core by studying the last shadow zone of the S wave.

References: http://www.seismo.unr.edu/ftp/pub/louie/class/100/interior.html