Natural phenomena such as rain, earthquakes, hurricanes or wind, they become disasters when they exceed a limit of normal (threshold, in English), usually measured through a parameter. This varies depending on the type of phenomenon Seismic Moment Magnitude (Mw) (Richter scale for earthquakes, Saphir-Simpson scale for hurricanes, etc.).
Disasters are caused by human activities that alter the normal environment. Some of these are: environmental pollution, erroneous and irrational exploitation of renewable natural resources such as forests and soil and non-renewable such as minerals, building houses and buildings in high risk areas.