Indo-Australian Plate
The Indo-Australian Plate and Pacific Plate boundary is the most complex boundary of the Macquarie Triple Junction region, due to the unique collision of the two plates creating two convergent boundaries separated by a transform boundary. The Puysegur Trench, which includes the Fjord Trench, is the southern region of the boundary closest to the Macquarie Triple Junction. The Puysegur Trench formed as the Indo-Australian Plate subducted beneath the Pacific plate. The Puysegur Trench ranges approximately 800 kilometers in length, from the most southern tip of the New Zealand Islands to the Macquarie Triple Junction. The Puysegur Trench makes contact with the Macquarie Fault Zone, which is associated with the Alpine Fault. The Alpine Fault is the right-lateral transform fault boundary separating the Puysegur Trench and the northern Kermadec Trench. The Alpine Fault runs through the majority of the southern island of New Zealand and is associated with New Zealand's frequent and intense earthquake history. The last major region of the Indo-Australian Plate and Pacific Plate Boundary is the Kermadec-Tonga subduction zone at which the Pacific Plate is subducted beneath the Indo-Australian Plate, in opposition of the Puysegur Trench. This convergent boundary has a rate of subduction of approximately 5.5-7.4 cm/yr.