Earthquakes are caused by the movement of the Earth鈥檚 crust at plate margins. They can destroy buildings and infrastructure, with devastating and deadly effects.
Many earthquakes occur every day somewhere on the planet. Most are so small that people do not feel them at all.
All earthquakes are measured on the Richter scaleThe measure by which the strength of earthquakes is determined.. This scale measures the magnitude of an earthquake. It is measured using a machine called a seismometerA machine that detects seismic waves caused by earthquakes., which produces a seismograph.
The Richter scale is normally numbered 1-10. It is a logarithmicA scale on a graph where the numbers increase exponentially. This means that the scale may read 1, 10, 100, 1000 instead of 1, 2, 3, 4. scale. Earthquakes measuring 1-2 on the scale are common and they are so minor that people cannot feel them. Earthquakes measuring upwards of 7 are less frequent but very powerful and can cause a lot of destruction.
The largest earthquake ever recorded was in Chile in 1960, it measured 9.5 on the Richter scale. The Richter scale is not very accurate in measuring these larger earthquakes and today scientists use the Moment magnitude scale (MMS)Used to measure the magnitude of earthquakes, in terms of the amount of energy released. which uses the same logarithmic scale but which more accurately measures the strength of larger earthquakes.