Earthquakes are ground shaking really hard and it creates a seismic waves which is the earth's crust is shaking really hard which is the same like Earthquakes. In 2004 the earthquake in Indian ocean causing a Tsunami. An Earthquake can cause buildings to collapse and the dirt can causes disease. Earthquakes can cause electricity wire to broke down and may cause fires with the spark.
Taken from: http://en.wikipedia.org/wiki/Earthquake