Do Now Question Why do you think the areas in pink and red have the highest earthquake risk?
In “earthquake zones” – places where a large number of faults are located MOST earthquake zones are at tectonic plate boundaries SOME earthquake zones can be in the middle of a tectonic plate Earthquakes occur at or near the surface of the Earth
Increased stress caused by tectonic plates pushing, pulling, or slipping past one another Watch this! Watch this! San Francisco
1. Elastic Deformation ◦ temporary change in the shape of a rock due to built-up stress 2. Elastic Rebound ◦ the sudden release of elastically deformed rock to its original shape ◦ happens when stress is applied to a rock that it can’t withstand ◦ energy is released in seismic waves creating an earthquake
Fastest Body wave – travels through the interior of the Earth Travels through solids and liquids Squeezes and stretches rock as it moves through it Nicknamed the “push-pull” wave Least powerful wave
2 nd fastest Body wave – travels through the interior of the Earth Travels through solids only! Pushes rock side- to-side as it snakes through it 2 nd most powerful wave
Slowest Surface wave – only travels along the ground surface of the Earth Causes rock to move in a circular motion like ocean waves (up, down, and around) Most powerful wave –it causes the most damage.
Seismic waves travel faster through objects that more dense ◦ Molecules are closer together and more tightly bonded Seismic waves travel slower through objects that are less dense ◦ Molecules are further apart so they have a weaker bond
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