Earthquakes are collisions and vibrations that can happen in the earth. Earthquakes happen when two plates slide past each other. The plates are very rough and as they slide against each other, the edges can sometimes get caught. The plates continue to move away, but are still captured at what is called the fault line (where the two plates are caught). After a while, the force pulling the plates becomes stronger than the friction holding them together, and they are forcefully detached. This creates vibrations which travel through the earth. Earthquakes can also happen when plates crash against each other.
Shock Waves: Waves of vibrations which travel through the earth.
Focus: Origin of the earthquake vibrations.
Epicenter: The surface point right above the focus.
There are two things to measure in earthquakes, there is the magnitude and intensity. The magnitude is the energy released, no matter how strong or weak the vibrations can be in certain areas affected. To measure the magnitude, we use a seismograph.
The measuring unit is called a Richter Scale. A seismograph looks like a needle on top of a long sheet of paper. The needle wobbles and creates lines on the rotating paper. In a Richter Scale, 1 is a very, very weak earthquake, so weak that it may not even be felt. As you go up through the digits, the magnitude increases. From 3.5 onward the earthquake is felt. The biggest earthquake ever recorded with the Richter Scale was 9.5 in Chile on May 22, 1960.
The intensity is the strength of the vibrations. These vary from area to area touched by an earthquake. Intensity is measured by the damage and effect an earthquake had on people, buildings, and the natural environment.
Earthquakes can cause a lot of damage if strong enough. Pipes can burst, roads can crack and break, some buildings can wobble, sway and break.