Gravity and magnetic modelling of the Hikurangi Plateau

Davy, Bryan; Wood, Ray

doi:10.1016/0025-3227(94)90117-1

Cited by 145 publications

(128 citation statements)

References 30 publications

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“…Furthermore, the arrival-time inversion for seismic velocity structure of Reyners et al (in prep. ), and gravity modelling offshore (Davy & Wood 1994), suggests that the crust of the subducted plate is c. 12 km thick. The aftershock zone extends from near the base of the subducted crust to c. 20 km into the subducted mantle (Fig.…”

Section: Discussionmentioning

confidence: 99%

The Ormond, New Zealand, earthquake of 1993 August 10: Rupture in the mantle of the subducted Pacific plate

Reyners

McGinty

Gledhill

1998

New Zealand Journal of Geology and Geophysics

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Data from temporary seismographs installed immediately after the M L 6.3 Ormond earthquake of 1993 August 10 have been used to determine the nature of faulting which took place during the event. The rupture began at 37 km depth, within the mantle of the subducted Pacific plate, and aftershocks extended from near the base of the subducted crust to c. 20 km into the subducted mantle. Aftershocks in the mantle decayed exceptionally rapidly compared with those in the crust of the subducted plate. This may reflect a hotter, more ductile mantle and/or relatively homogeneous rupture within the mantle during the mainshock. Aftershocks within the mantle show a variety of thrusting mechanisms. Focal mechanisms of aftershocks within the subducted crust indicate that compression along strike dominates over slab pull, and that the down-dip stress has a similar magnitude to the vertical stress. This suggests that, at least after the Ormond earthquake, the tectonic stress coupled across the plate interface is rather low.

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Section: Discussionmentioning

confidence: 99%

The Ormond, New Zealand, earthquake of 1993 August 10: Rupture in the mantle of the subducted Pacific plate

Reyners

McGinty

Gledhill

1998

New Zealand Journal of Geology and Geophysics

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“…1) [16][17][18][19] . Subduction of 15-23-km thick, altered and buoyant Hikurangi Plateau crust, that is host to large seamounts 19,20 , must not only have a strong effect on tectonic erosion and the local plate stress regime, but also on volatile element budgets in the overlying mantle.…”

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confidence: 99%

Subduction of the oceanic Hikurangi Plateau and its impact on the Kermadec arc

et al. 2014

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Large igneous province subduction is a rare process on Earth. A modern example is the subduction of the oceanic Hikurangi Plateau beneath the southern Kermadec arc, offshore New Zealand. This segment of the arc has the largest total lava volume erupted and the highest volcano density of the entire Kermadec arc. Here we show that Kermadec arc lavas south of B32°S have elevated Pb and Sr and low Nd isotope ratios, which argues, together with increasing seafloor depth, forearc retreat and crustal thinning, for initial Hikurangi Plateau-Kermadec arc collision B250 km north of its present position. The combined data set indicates that a much larger portion of the Hikurangi Plateau (the missing Ontong Java Nui piece) than previously believed has already been subducted. Oblique plate convergence caused southward migration of the thickened and buoyant oceanic plateau crust, creating a buoyant 'Hikurangi' mélange beneath the Moho that interacts with ascending arc melts.

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“…Seismicity data [e.g., Robinson, 1986;Bannister, 1988] and gravity modeling [Davy and Wood, 1994 All new and previously existing seismic reflection profiles have been interpreted in light of the new swath imagery data. Structures were correlated between seismic profiles with confidence using both detailed bathymetric and side-scan sonar images, and structural and morphological maps compiled at a scale of 1:200,000.…”

mentioning

confidence: 99%

Rates and mechanics of rapid frontal accretion along the very obliquely convergent southern Hikurangi margin, New Zealand

Barnes¹,

Lépinay²

1997

J. Geophys. Res.

133

115

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Abstract. Analysis of seismic reflection profiles, swath bathymetry, side-scan sonar imagery, and sediment samples reveal the three-dimensional structure, morphology, and stratigraphic evolution of the central to southern Hikurangi margin accretionary wedge, which is developing in response to thick trench fill sediment and oblique convergence between the Australian and Pacific plates. A seismic stratigraphy of the trench fill turbidites and frontal part of the wedge is constrained by seismic correlations to an already established stratigraphic succession nearby, by coccolith and foraminifera biostratigraphy of three core and dredge samples, and by estimates of stratigraphic thicknesses and rates of accumulation of compacted sediment. Structural and stratigraphic analyses of the frontal part of the wedge yield quantitative data on the timing of inception of thrust faults and folds, on the growth and mechanics of frontal accretion under variable convergence obliquity, and on the amounts and rates of horizontal shortening. The data place constraints on the partitioning of geological strain across the entire southern Hikurangi margin. The principal deformation front at the toe of the wedge is discontinuous and represented by right-stepping thrust faulted and folded ridges up to 1 km high, which develop initially from discontinuous protothrusts. In the central part of the margin near 41 øS, where the convergence obliquity is 50 ø, orthogonal convergence rate is slow (27 mm/yr), and about 75% of the total 4 km of sediment on the Pacific Plate is accreted frontally, the seismically resolvable structures within 30 km of the deformation front accommodate about 6 km of horizontal shortening. At least 80% of this shortening has occurred within the last 0.4 __. 0.1 m.y. at an average rate of 12 __. 3 mm/yr. This rate indicates that the frontal 30 km of the wedge accounts for about 33-55% of the predicted orthogonal contraction across the entire plate boundary zone. Despite plate convergence obliquity of 50 ø , rapid frontal accretion has occurred during the late Quaternary with the principal deformation front migrating seaward up to 50 km within the last 0.5 m.y. (i.e., at a rate of 100 km/m.y.). The structural response to this accretion rate has been a reduction in wedge taper and, consequently, internal deformation behind the present deformation front. Near the southwestern termination of the wedge, where there is an along-the-margin transition to continental transpressional tectonics, the convergence obliquity increases to >56 ø, and the orthogonal convergence rate decreases to 22 mm/yr, the wedge narrows to 13 km and is characterized simply by two frontal backthrusts and landward-verging folds. These structures have accommodated not more than 0.5 km of horizontal shortening at a rate of < 1 mm/yr, which represents < 5% of the predicted orthogonal shortening across the entire plate boundary in southern North Island. The landward-vergent structural domain may represent a transition zone from rapid frontal accretion associ...

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Gravity and magnetic modelling of the Hikurangi Plateau

Cited by 145 publications

References 30 publications

The Ormond, New Zealand, earthquake of 1993 August 10: Rupture in the mantle of the subducted Pacific plate

The Ormond, New Zealand, earthquake of 1993 August 10: Rupture in the mantle of the subducted Pacific plate

Subduction of the oceanic Hikurangi Plateau and its impact on the Kermadec arc

Rates and mechanics of rapid frontal accretion along the very obliquely convergent southern Hikurangi margin, New Zealand

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