Earthquakes are natural disasters caused by the shifting of Earth's plates; they have been included in the SimCity series from the beginning as disasters with the potential to start fires and destroy a city.
Until The Sims 3: Ambitions, earthquakes were not included in The Sims series. In Ambitions, it is unknown what causes earthquakes, or whether they are Sim-made or natural. Regardless, they can cause damage and destruction in a neighborhood, but this can be controlled by Sims in the Firefighter career.
When an earthquake occurs, the screen will shake, and a message will pop up saying that the Sim should check in with the fire station to see if they can help out.
Earthquakes can cause fires and gas leaks, and Sims can be buried in rubble after an earthquake. While working on the disaster, the Sim will most likely encounter more than one household with trapped Sims, as well as other havoc. Responding to an earthquake is a good career move for Sims with the Firefighter Hero lifetime wish, as they will usually save 4 to 10 Sims from rubble.
Earthquakes can be caused by Sims, but with the use of cheating: A Sim with the firefighter profession can type in "testingcheatsenabled true" and shift click any lot to spawn job and click earthquake or any other of the disasters listed. This will cause an earthquake if this cheat is selected on the right lot.
In The Sims 3 (console) earthquakes comes in a form of a bad karma power, "Quake Maker", which causes the screen to shake with objects breaking and fire erupting around the lot while leaving the witnessed sims terrified. To unlock it, the player must spend 20 karma points on it.