Where do earthquakes occur?
Earthquakes can happen all over the world. 80% of the world’s earthquakes happen in the Pacific Ocean near Japan in a place called the Ring of Fire.
It is important for countries that suffer from earthquakes to build houses that are difficult to collapse. In Japan, many buildings are designed to wobble when an earthquake hits them.
Epicentres and hypocentres
Hypocentre or focus: is the place where an earthquake begins. It is below the Earth’s surface.
Epicentre: is the place above where an earthquake begins (above the hypocentre).
Seismic waves
Shock waves from earthquakes are called seismic waves. They travel through the ground and move very quickly, 20 times faster than the speed of sound!
Measuring earthquakes
To know how big an earthquake is, scientists use a special machine called a seismograph. A seismograph measures the size of seismic waves. The speed of seismic waves helps scientists locate the epicentre of an earthquake. Scientists who study earthquakes are called seismologists.
A special scale is used to measure how bad an earthquake is. It’s called the Moment Magnitude Scale or MMS (once called the Richter scale).
The higher the MMS scale, the larger the earthquake.
An earthquake rated 3-5 is not strong.
An earthquake rated 5-7 is medium to strong.
An earthquake rated 7-8 is very strong.
An earthquake rated 8 or above is super strong.
Earthquakes that measure less than 3 are so light they are normally not even noticed.
Fun fact:
A long time ago, the ancient Chinese invented a very clever device that could help find out where an earthquake began. It looked like a jar with dragons on the top. Surrounding the jar were frogs with their mouths open.
When an earthquake occurred, a ball would drop from a dragon’s mouth and fall into a frog’s mouth. The position of the frog which received the ball showed the direction of the earthquake!
Did you know?
- Scientists cannot predict earthquakes. They can only point out where an earthquake is likely to occur.
- The most powerful earthquake ever recorded on Earth happened in 1960 in Valdivia, Chile. It had a magnitude of 9.5!
- About 10,000 people die in earthquakes every year.
- In ancient Greece, people believed earthquakes were caused by Poseidon, the god of the sea. When he was angry, Poseidon would strike the ground with his trident and set off an earthquake. He was often nicknamed 'Earth-Shaker'.
