The main shock was preceded for two weeks by earthquake swarms in two areas of the Bay of Plenty. A swarm started on 21 February off-shore from
Maketu, near
Te Puke, 40 kilometres from the main shock's epicentre, and another swarm started on 26 February between Matatā and
Thornton, very close to the epicentre. Then there was a 5.2 earthquake at 1.35 pm on 2 March, followed by the main shock seven minutes later. The largest
aftershock measured 5.6 and struck nine minutes later at 1.51 pm. Eleven ground-surface ruptures occurred in the Rangitaiki Plains, though no
active faults had previously been recognised on the Plains. The largest rupture, the Edgecumbe Fault, was long and formed on, and extended, a late
Holocene fault scarp. The intense ground shaking led to a large number of ground surface failures, including sand boils, ridge-top shatters and debris avalanches on steeper slopes. The Rangitaiki Plains is part of the
Whakatāne Graben and both lie within the
Taupō Volcanic Zone, which is widening and subsiding. During the Edgecumbe earthquake, the area widened by 1.2 metres and dropped in height by . The most damage was in the towns of Edgecumbe,
Te Teko,
Kawerau, Matatā and Thornton, where chimneys toppled and poorly constructed houses were seriously damaged. The
foreshock seven minutes before the main shock had cut the power supply, and many people had moved away from heavy machinery and out of buildings that then collapsed in the main earthquake. ==Gallery==