Three‐stage massive gravitational collapse of the emergent imbricate frontal wedge, Hikurangi Subduction Zone, New Zealand

Abstract

A large-scale east-facing Quaternary gravitational collapse is affecting the otherwise thrust-faulted terrain of coastal southern Hawke's Bay on the east coast of North Island of New Zealand, involving an area >30 km long and up to 6 km inland from the coast, but also extending offshore. The western limit of the collapse structure onshore is represented by a footwall escarpment forming the eastern margin of the Maraetotara Plateau (av. elevation 500 m a.s.l.). To the east of this escarpment, the disposition of the Pliocene Te Aute Limestone within a complex extensional zone reflects numerous northeast-southwest-trending normal faults (some Holocene active) with the development of horst and graben, fault-angle depressions, synclinal folds, fissured zones, and large parasitic landslides. Listric normal faulting is reflected by the back-tilting of large blocks up to several kilometres in length, near the centre of the gravitational collapse. Horizontal extension across the gravitational collapse domain is calculated at between 15 and 20%. West of the footwall escarpment, the Maraetotara Plateau defines a separate structural domain with horizontal extension of between 2 and 5%, inferred to be related to bending moment faults driven by regional arching accompanying uplift. A fundamental contrast exists between active extensional structures onshore and the mainly contractional structures (asymmetrical anticlines, reverse and thrust faults) offshore. A tectonically driven model involving underplating of trench fill best explains the large-scale gravitational collapse of this part of the emergent imbricate frontal wedge of the Hikurangi Subduction Zone margin.

Controls on active forearc basin stratigraphy and sediment fluxes: The Pleistocene of Hawke Bay, New Zealand

“…Such features include the deep-seated Kahuranaki Klippe and Kaiwhakapiripiri Range landslides within the coastal ranges (Pettinga, 1982(Pettinga, , 2004; several deep-seated landslides along the Esk River in the foothills; and a multitude of smaller slides within the Kidnappers Group (this study; Fig. 8).…”

High-resolution view of active tectonic deformation along the Hikurangi subduction margin and the Taupo Volcanic Zone, New Zealand

“…Highly active normal faulting is observed in the Taupo Volcanic Zone of the central North Island (see Villamor & Berryman 2001), which undergoes intraarc rifting at rates ranging from a few millimetres per year in the southern TVZ to as high as 15 mm a -1 in the northern TVZ near the Bay of Plenty coastline (Wallace et al 2004;Lamarche et al 2006). Normal faulting is also observed at a number of locations within the forearc (Cashman & Kelsey 1990;Chanier et al 1999;Berryman et al 2009;Pettinga 2004), despite the fact that most of the Hikurangi forearc deformation is dominated by transpression. Most of the forearc extension is localised to the rapidly uplifting Raukumara Ranges (Berryman et al 2009) and in the Maraetotara Plateau area (Cashman & Kelsey 1990;Pettinga 2004) (Figure 1).…”

Extension at the coast of the Makran subduction zone (Iran)

“…Armijo & Thiele, ; Sage, Collot, & Ranero, ), sediment underplating (Platt, Leggett, Young, Raza, & Alam, ), gravitational collapse (e.g. Pettinga, ) and coseismic relaxation (e.g. Hardebeck, ; Wang & Hu, ).…”