How Earthquakes Happen - an explanation by room 4

How Earthquakes Happen

An Earthquake is when two tectonic plates, under the earth’s surface rub together, causing the earth to shake, sending shock waves out from the epicentre.

Under the Earth’s surface are a number of plates, which we call ‘Tectonic Plates.’ They are not joined and they are constantly moving and sliding into each other. Their edges are rough and rugged and sometimes they get stuck on each other. When they come apart there is a jerk and a shake that causes an earthquake and the energy sends out shock (seismic) waves which ripple out from the middle (epicentre), causing everything on the earth’s surface to move and shake. The areas where tectonic plates meet are called ‘fault lines’ and this is where most earthquakes occur.

When an earthquake happens, there is a rumbling sound and the earth starts shaking. Sometimes you can see animals and birds behaving strangely as they are terrified of the shaking ground. Landslides can occur, cracks can show in the earth’s surface, buildings can be destroyed and people can be killed by earthquakes. Earthquakes can cause a lot of damage, especially when they hit towns and cities. It can take billions of dollars to repair damage. Fires can also occur as the result of an earthquake when power lines fall down, and when damaged wiring comes back on when power is restored. The trouble with fires is that roads are blocked and water supplies are disrupted so fire trucks can’t always put out the fires, which adds to the damage. The amount of damage caused depends on how big the earthquake is.

An earthquake is measured by a special machine called a ‘richter scale.’ As an earthquake happens a seismograph shakes too. Depending on how bad the earthquake is, it makes short or long wiggles. A short wiggle is a smaller quake, and a long wiggle is a large quake. A magnitude 2 earthquake can not be felt, but a magnitude 7 earthquake will cause a lot of damage and could kill a lot of people.

Following an earthquake will come a number of aftershocks, some of which can almost equal the magnitude of the original shock. These are caused by the resettling of the earth. Aftershocks can cause further damage to already weakened and damaged buildings or structures.

Scientists can not predict earthquakes, and they are not ever likely to be able to. In order for us to prepare for earthquakes we should have a survival kit in our houses, and our schools and businesses. We need to be able to eat and drink and have torches and cookers, because we might be without food, water and power for a great while. Everybody needs to have an earthquake plan, and practice this drill regularly so that everyone knows what to do in the event of an earthquake.

Earthquakes can occur at anytime, we have no control over them and we can not predict them. An earthquake can be very dangerous and cause a lot of damage. It is important that we are prepared in the event of a major earthquake.