GNS Science has determined a nine percent chance of another earthquake similar in size to Monday's Eketahuna quake hitting the area again in the next 30 days.
The research group said a magnitude six or seven quake could strike at the same depth as the current aftershocks and in a nearby part of the Pacific plate.
Alternatively, GNS said the quake could be centred at a shallower depth in the overlying Australian plate.
It said if a shallower earthquake occurred, there may be stronger shaking at the surface than there was on Monday.
The research group said there was a less than one percent chance of a magnitude seven or greater earthquake striking.