do now question why do you think the areas in pink and red have the highest earthquake risk?
TRANSCRIPT
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
Where do earthquakes occur?
Increased stress caused by tectonic plates pushing, pulling, or slipping past one another
Watch this!
What causes earthquakes?
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
What leads to 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
PRIMARY (P) WAVES
2nd fastest
Body wave – travels through the interior of the Earth
Travels through solids only!
Pushes rock side-to-side as it snakes through it
2nd most powerful wave
SECONDARY (S) WAVES
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.
SURFACE (L) WAVE
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
Seismic Waves
United States daily earthquakes
Live worldwide earthquake data
Earthquakes happen everyday!