Scientists at Victoria University have discovered slow moving earthquakes, that can last up to half an hour, are taking place beneath the South Island alpine fault.
Geophysics Professor Tim Stern says an apparent absence of earthquakes in the central section of the fault has puzzled scientists for decades and this discovery proves there is activity down there.
He says creeping earthquakes can be felt only by highly sensitive recording equipment and usually measure about magnitude 1.0.
Professor Stern says it is not known how these tremors will affect the activity of regular earthquakes, but there are two opposing theories.
He says the tremors could either build up stress, possibly triggering a major quake, or relieve it by acting as a release valve.