The principle behind earthquake early warnings is fairly straightforward. Earthquakes begin with tremors called P-waves that have short wavelengths and generally do little damage; they may not even be felt by humans. Seconds later, the exact number of seconds depends on distance from the quake's epicenter, longer-wavelength tremors known as S-waves arrive and inflict damage as they shake buildings and landmasses. Early warning systems consist of seismographs that detect the P-waves and send out electronic alerts.
Japan, an earthquake-prone country, launched an early warning system in October 2007 that delivers warning via mass media, including television and the Internet. Other countries like Taiwan and Mexico are developing systems on the same basis.

Additionally, diverse early warning projects are dealing with the implementation of this warning technology on the local scale. An example is the German development association for international earthquake prevention measures (IEP e.V.). It is a non-profit association, which supports projects concerned with earthquake prevention measures.