[3] The northern part of this complex is an extension of New Zealand's Alpine Fault which becomes the Puysegur Trench and ridge to its east.

However both west of Macquarie Island and to its east towards the southern tip of the Campbell Plateau there has been some historic earthquake activity outside the zone.

[15] In the Hjort Trench region the plate boundary is definitely under the stress condition of transpression as earthquake focal mechanisms are both thrust and dextral strike-slip types as found in such areas.

[16] To the south of the Hjort Trench there is relatively low grade seismic activity in the Emerald Fault Zone and towards the Macquarie triple junction.

[2] This event to the west of the plate boundary was close to the transition from oblique subduction at the Puysegur Trough to strike slip, with some compression, on the Macquarie Ridge.

It is believed these large events are because the transition to oblique convergence with subduction is putting the area of what has been called the Macquarie Block under significant strain that is eventually relieved by major failure reactivating past transform faults in the oceanic crust of the Tasman sea floor.

The Australia-Pacific plate boundary is now understood to be along the crest of the ridges rather than in the troughs with a zone of deformation up to 100 km (62 mi) wide.

[24] This central area has had up to 290 km (180 mi) right lateral displacement since ocean floor spreading ceased at about 10 million years ago.

[16] This regions previous tectonic evolution has also been studied in detail as it is related to the Macquarie triple junction which was created about 47.91 million years ago.

It is postulated that because the lithosphere would cool and strengthen usually with mid oceanic ridge formation, that if such tectonic inversion is not rapid, it does not lead to the relative simplicity seen at say the Kermadec-Tonga subduction zone.

[27] The process is summarised as:[4] This last stage has been difficult to characterise as the usual approach through magnetic anomaly studies only allowed a good time for the central McDougall and Macquarie segments spreading ceasing by 24 million years ago and either end was only constrained to the 30 million years ago estimate.

[6] And so to a degree the apparent clash with evidence that the Puysegur subduction initiated at 20 million years ago[27] is less challenging to explain.

[6] Maps of this tectonic activity have been modelled from 42 million years ago to the present showing the evolving spreading center, its extinction and fault zone relationships.