The Wellington region is tectonically active and criss-crossed by many faultlines. While we often feel small earthquakes that don't cause much damage, many of the active faults in the region are actually capable of producing large earthquakes.

In 1855, the Wairarapa Fault ruptured causing a magnitude 8 (on the richter scale) earthquake. About 5000 km ² of land was shifted vertically, with uplift of 6 metres near Turakirae Head and 1-2 metres in the Wellington harbour. The main quake shook for 50 seconds and was followed by hundreds of aftershocks greater than magnitude 5 in the following few weeks.

A large, shallow earthquake along the Wellington fault, say magnitude 7.4, would cause strong shaking and considerable damage around the region. If it happened during the day there could be about 500 deaths, 4,000 injuries and perhaps 1,800 people trapped.

If the earthquake hit at night, fewer people would be hurt. We could expect over 100,000 buildings to be damaged in some way. It could cost $4 billion to repair and rebuild Wellington and the surrounding areas.