A strong earthquake that shook the Tararua area and which was felt across the lower North Island has prompted closer monitoring of seismic activity in the area.
Seismologists are now specifically investigating whether the 5.1 magnitude quake, that struck at 1.07pm at a depth of 25km, about 25km east of Pongaroa, might have done anything to activate the huge "megathrust" fault that runs along the tectonic plate boundary that New Zealand straddles.
More than 800 people reported feeling the quake on GeoNet.
It followed a "moderate" 3.7 quake 5km southeast of Eketahuna and preceded a "weak" 3.0 quake 30km east of Pongaroa at 1.25pm.
On GeoNet's Facebook page, people reported feeling the quake in areas as far away as Wanganui, Paraparaumu, Carterton, Palmerston North and Stokes Valley.