The outer layer of the earth, the crust, is composed of many pieces that move relative to one another. The tectonic plates either rub together on the sides, push from each other, or push under each other. All of these movements on the plates boundaries generate tension that is released by an earthquake. Different types of earthquakes characterize different plate boundaries. In order to measure the magnitude of an earthquake, a so-called Richter scale is used, it ranges from 1 to 10.

The biggest earthquakes are not necessarily the deadliest. The deadliest earthquakes occur in densely populated inhabited areas, that are not built to resist earthquakes. For example, the largest earthquake on record, was in Chile in 1960 (9,5 on Richter), where 2.000 people died, but the deadliest earthquake was in Haiti in 2010 (7 on Richter), and there was a loss of 316.000 people.