b'The Australian continent: A geophysical synthesisFeatureembayments and salients left over from peri-GondwananZealand, where the Pacific Plate is being subducted, giving rise fragments that broke away in the Mesozoic era and now formto many of the Earths deep earthquakes. In New Zealand itself, the basement in Southeast Asia. (Huston et al. 2012). there is oblique subduction along the east coast of the North Island, with collision through the South Island moderated by the Alpine Fault. Beneath the Fiordland region of the South Island, Tectonic setting the Australian Plate is subducting at the Puysegur Trench. This The Australian Plate is undergoing a complex set of interactionsshort subduction zone links to a largely strike-slip boundary with its neighbours. To the south, an active spreading centrethat passes Macquarie Island and links to the boundaries of the separates the Australian Plate from the Antarctic Plate. ThisAntarctic Plate (DeMets et al. 2010).margin developed with the break-up of Gondwana aroundThe Australian Plate is subducting beneath the Pacific Plate 99 Ma, with full separation by 35 Ma. Following a major platealong its northeastern margin at the New Hebrides and reorganisation in the Pacific Ocean at around 40 Ma, AustraliaSolomon Trenches. The northern boundary of the Australian acquired its present northnortheast trajectory. Australia hasPlate is complex. Continental Australia is colliding with migrated more than 3000 km along this path at a rate of 67 cm/ the Pacific Plate through New Guinea. But to the west, the yr over the past 45 Myr, which, as previously indicated, makes itinteraction is with the Eurasian Plate with collision in the Banda the fastest moving continent since the Eocene (Tregoning 2003). Arc region and subduction of the Australian Plate beneath Following break-up, Australias initial drift was to the northwest.Indonesia at the Java and Sumatra trenches (Figure 2).Ridge subduction in the northwest Pacific at around 52 MaSubduction in the Banda Arc region may well already have come resulted in the termination of spreading in the Tasman Sea,to a halt with the arrival of thick buoyant Australian lithosphere and a change in the Australian Plate vector to its present-daythat cannot readily descend to depth. The western boundary of northerly orientation. Sea floor spreading in the Southernthe plate is a diffuse zone called the Capricorn Plate, which lies Ocean accelerated at around 45 Ma, but it was not until 35 Mabetween the Australian Plate and the Indian Plate further to the that full separation of Australia and Antarctica occurred.northwest (DeMets et al. 2010).Australia, as a separate continent, was released from theThe boundary forces acting upon the Australian Plate vary remnants of Gondwana and commenced a northward passagefrom tension in the south and southwest to compression to meet Asia. in the east and north. The present stress state is largely The eastern boundary of the Australian Plate with the Pacificcontrolled by compression originating from the three main Plate is marked by the TongaKermadec Trench, north of Newcollisional boundaries located in New Zealand, Indonesia Figure 2.Tectonic setting of Australia, with major seabed features and plate boundaries, superimposed on the age of the sea floor (Mller et al. 2008). The mid-ocean ridges are indicated with a double line and the sense of subduction is indicated.41 PREVIEW APRIL 2019'