1. Earthquakes Chapter 12 Section 1

2. What is an earthquake?
Earthquakes are movements of the ground caused by a sudden release of energy when rocks along a fault move.
Seismology – the study of earthquakes and seismic waves

3. Where do earthquakes occur?
Earthquakes can occur at plate boundaries or along fault lines in Earth’s crust.
A fault is a break in a body of rock along which one block slides relative to one another.

4. Where do earthquakes occur?
Earthquakes typically occur along transform boundaries when tectonic plates slide past one another.
However, the strongest earthquakes occur at convergent boundaries due to the amount of increased stress on the rock.

5. Where do earthquakes occur?
Earthquakes can be felt over large areas although they usually last less than one minute.

6. Anatomy of an Earthquake
FOCUS: the location within Earth along a fault line where the first motion of an earthquake occurs. (point of origin)
EPICENTER: the point on Earth’s surface directly above the focus.

7. There are TWO categories of SEISMIC WAVES
During an earthquake rocks release energy in the form of vibrations called seismic waves
There are TWO categories of SEISMIC WAVES
Body waves – travel through the Earth
primary and secondary waves
Surface waves- travel along the Earth’s surface
Love and Rayleigh waves

8. Body Waves Primary Waves (P waves) Fastest
Travels through solids, liquids and gases
First waves to be detected during an earthquake
Moves rock back and forth, which stretches and squeezes the rock.
Longitudinal wave

9. Body Waves Secondary Waves (S waves) Slower than P waves
Second waves to be detected during an earthquake
Stretches rock moves rocks side to side
Travels ONLY through solids (can not travel through Earth’s outer core)
Transverse wave

10. Body Waves - P and S
S waves can ONLY travel through solids. They can not travel through the liquid outer core and will change direction when they reach that layer.
P waves can travel through solid, liquids and gasses. That means they can travel through all of Earth’s layers.

11. Surface Waves Slowest moving waves
Can cause the most damage during an earthquake
There are two types of Surface Waves
Love Waves (L) – side to side motion
Rayleigh Waves (R) – rolling elliptical motion

13. Earthquakes
Brain Pop: Earthquakes
Discovery Education: Earthquakes