In the present, the most widely used scale is known as the Moment Magnitude Scale (Mw). As you know, the Earth is formed by pieces, like a puzzle, these pieces are called tectonic plates and they are in constant movement. When tectonic plates collide against each other an earthquake happens. The Moment Magnitude Scale uses a number (from 1 to 10) to show how much energy an earthquake releases. For example, people normally feel the earthquake when it has an scale of 2.5 to 3, which are considered minor earthquakes, but an earthquake with a higher scale (like 8 or 9) can easily destroy cities, cause major damages and be followed by tsunamis.