Open AccessGeometry of the Hikurangi subduction thrust and upper plate, North Island, New Zealand
Author(s) -
Barker Daniel H. N.,
Sutherland Rupert,
Henrys Stuart,
Bannister Stephen
Publication year - 2009
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2008gc002153
Subject(s) - geology , subduction , forearc , accretionary wedge , seismology , slab , thrust fault , episodic tremor and slip , wedge (geometry) , tectonics , paleontology , geometry , mathematics
We use 2800 line km of seismic reflection data to map the offshore character and geometry of the Hikurangi subduction thrust and outer forearc wedge to depths of ∼15 km. For 200 km along‐strike south of Hawke Bay, the subduction thrust is relatively smooth, dips less than 8°, and the wedge is characterized by accretion of young sediment and topographic slopes of less than 3°. In Hawke Bay and north for 200 km, a kink in the subduction thrust is apparent, with a downdip increase in dip to angles greater than 8° at depths of 10–15 km; there is a corresponding steepening of the topographic slope to greater than 3° outboard of the kink and the wedge is characterized by lithified sedimentary rock and slope failure. The kink in the subduction thrust is a locus of inherent weakness in the subducting slab; we suggest its occurrence relates to a northward increase in subduction rate that controls initial slab dehydration and fluid release rates and hence intraslab deformation patterns. The subduction thrust geometry, in combination with a northward increase in subducting plate roughness and decrease in the amount of sediment accreted, causes the observed spatial change in character of the subduction thrust and forearc wedge.