1. Earthquakes
Sections 6.2 and 6.3

2. Section 6.2 – Recording Earthquakes
Seismic waves are recorded using a seismograph
A seismograph is made of 3 separate devices
One measures up and down movement
While the other 2 measure North-South and East-West movements

3. Section 6.2 – Recording Earthquakes
There are 3 kinds of seismic waves
Primary Waves (P waves) – move the fastest and can travel through solids and liquids. P waves are detected first
Secondary Waves (S waves) – are slower and can only travel through solid rock. S waves are detected second
Surface Waves – are the slowest. They occur when P and S waves reach the surface and cause lots of Damage

4. Section 6.2 – Recording Earthquakes
It takes 3 seismographs to locate the epicenter of an earthquake
The difference in amount of time it takes the P and S waves to reach each seismograph determines how far away the earthquake occurred.

5. Section 6.2 – Recording Earthquakes
Magnitude is a measure of the energy released by an earthquake and it describes the amount of ground motion
The Richter scale shows how much damage is expected by the earthquake

6. Section 6.2 – Recording Earthquakes
Large earthquakes have a magnitude above 7
Moderate are between 6 and 7
Minor are between 2.5 and 6
Microquakes are below 2.5 and aren’t felt by people

7. Section 6.3 – Earthquake Damage
During severe earthquakes you would be much safer in an open field than in a city of skyscrapers
Large buildings sway and the fall over
Buildings built on loose soil are more likely to fall than those on solid ground

8. Section 6.3 – Earthquake Damage
A Tsunami is formed when a major earthquake happens on the ocean floor
A tsunami is a giant ocean wave
Tsunamis can also be caused by under water landslides

9. Section 6.3 – Earthquake Damage
Earthquakes are very hard to predict
Along some faults, scientists have identified zones of rock that are locked in to position
This is called a seismic gap.