| HOW
SCIENTISTS MEASURE EARTHQUAKES The place in the Earth where an earthquake begins is called the focus. The point on the surface directly above the focus is called the epicenter. The epicenter is where people feel an earthquake most strongly. Scientists have set up instruments all around the Earth to measure earthquakes. These instruments record the ground movement where they are, as the shaking from an earthquake travels out in waves from the focus where the earthquake began. By combining this information with data about how fast waves travel through the earth, scientists can figure out where and at what time an earthquake occurred, and how strong it was. |
 A seismograph records earth movements during an earthquake. |
| Type of Damage | Magnitude (Richter Scale) |
Earthquakes per Year Worldwide (average) |
| Great | 8 and higher | 1 |
| Major | 7 - 7.9 | 20 |
| Strong | 6 - 6.9 | 120 |
| Moderate | 5 - 5.9 | 800 |
| Light | 4 - 4.9 | 6,200 |
| Minor | 3 - 3.9 | 49,000 |
| Very Minor | < 3.0 | More than 3 million |
