The structure and seismic potential of the Aotea and Evans Bay faults, Wellington, New Zealand

Barnes, Philip M.; Nodder, Scott D.; Woelz, Susanne; Orpin, Alan R.

doi:10.1080/00288306.2018.1520265

Cited by 5 publications

(2 citation statements)

References 46 publications

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“…It is also evident that better and more comprehensive characterisation of soil and rock shear wave velocity (and other properties) is necessary within the Wellington region in order to maximise the utility of numerical simulations and better understand previous empirical observations. For example, it should be noted that the 2D model domain passes through the Aotea Fault [29], though the effects of this fault on the basin geometry are not considered in the current study. The Semmens et al [9] basin model that informs the 2D models developed here did not make consideration for the portion of the Aotea Fault that impacts the model domain, and the recentlypublished update of the Semmens et al model by Kaiser et al [30] was not published at the time that the 2D model development was undertaken for this study.…”

Section: Discussionmentioning

confidence: 99%

Basin effects and limitations of 1D site response analysis from 2D numerical models of the Thorndon basin

McGann

Bradley

Wotherspoon

et al. 2021

BNZSEE

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Plane strain (2D) finite element models are used to examine factors contributing to basin effects observed for multiple seismic events at sites in the Thorndon basin of Wellington, New Zealand. The models consider linear elastic soil and rock response when subjected to vertically-propagating shear waves. Depth-dependent shear wave velocities are considered in the soil layers, and the effects of random variations of soil velocity within layers are modelled. Various rock shear wave velocity configurations are considered to evaluate their effect on the modelled surficial response. It is shown that these simple 2D models are able to capture basin reverberations and compare more favourably to observations from strong motion recordings than conventional 1D site response models. It is also shown that consideration of a horizontal impedance contrast across the Wellington Fault affects spectral response and amplification at longer periods, suggesting the importance of this feature in future ground motion modelling studies in the Wellington region.

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Section: Discussionmentioning

confidence: 99%

Basin effects and limitations of 1D site response analysis from 2D numerical models of the Thorndon basin

McGann

Bradley

Wotherspoon

et al. 2021

BNZSEE

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“…Slow slip events FIGURE 1 Tectonic setting of New Zealand showing plate boundary components and motion rates (DeMets et al, 1990;DeMets et al, 1994;DeMets et al, 2010), and Hikurangi subduction interface coupling of the North Island -regions in blue are weakly coupled (undergoing aseismic slow slip), regions in red are fully elastically coupled (locked) (from Wallace et al, 2012). Also shown are active crustal faults (red lines) (onshore faults from the New Zealand Community Fault Model (NZ CFM) - Seebeck et al, 2022; offshore active faults from Barnes and Audru, 1999;Barnes et al, 2002;Nodder et al, 2007;Mountjoy et al, 2009;Barnes et al, 2010;Pondard and Barnes, 2010;Mountjoy and Barnes, 2011;Barnes et al, 2019;.…”

Section: Tectonic Uplift Processes At Subduction Marginsmentioning

confidence: 99%

Causes of permanent vertical deformation at subduction margins: Evidence from late Pleistocene marine terraces of the southern Hikurangi margin, Aotearoa New Zealand

et al. 2023

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Theoretical studies of the seismic cycle at convergent plate boundaries anticipate that most coseismic deformation is recovered, yet significant permanent vertical displacement of the overriding plate is observed at many subduction margins. To understand the mechanisms driving permanent vertical displacement, we investigate tectonic uplift across the southern Hikurangi subduction margin, Aotearoa New Zealand, in the last ∼200 ka. Marine terraces preserved along the Wellington south coast have recently been dated as Marine Isotope Stage (MIS) 5a (∼82 ka), 5c (∼96 ka), 5e (∼123 ka) and 7a (∼196 ka) in age. We use these ages, together with new reconstructions of shoreline angle elevations, to calculate uplift rates across the margin and to examine the processes responsible for their elevation. The highest uplift rate—1.7 ± 0.1 mm/yr–and maximum tilting—2.9° to the west–are observed near Cape Palliser, the closest site to (∼50 km from) the Hikurangi Trough. Uplift rates decrease monotonically westward along the Palliser Bay coast, to 0.2 ± 0.1 mm/yr at Wharekauhau (∼70 km from the trough), defining a gently west-tilted subaerial forearc domain. Locally, active oblique-slip upper-plate faults cause obvious vertical offsets of the marine terraces in the axial ranges (>70 km from the trough). Uplift rates at Baring Head, on the upthrown side of the Wairarapa-Wharekauhau fault system, are ∼0.7–1.6 mm/yr. At Tongue Point, uplift on the upthrown side of the Ōhāriu Fault is 0.6 ± 0.1 mm/yr. Dislocation and flexural-isostatic modelling shows that slip on faults within the overriding plate—specifically the Palliser-Kaiwhata Fault and the Wairarapa-Wharekauhau fault system—may dominate uplift in their immediate hanging walls. Depending on their slip rate and geometry, slip on these two upper-plate fault systems could plausibly cause >80% of late Pleistocene uplift everywhere along the south coast of North Island. Our modelling suggests that subduction of the buoyant Hikurangi Plateau contributes uplift of 0.1–0.2 mm/yr and uplift due to sediment underplating at Tongue Point and Wharekauhau is likely ≤0.6 mm/yr but could be significantly lower. Earthquakes on the subduction interface probably contribute ≤0.4 mm/yr of late Pleistocene uplift, with ≤10% of uplift due to each earthquake being stored permanently, similar to other subduction zones. These results indicate a significant contribution of slip on upper-plate faults to permanent uplift and tilting across the subduction margin and suggest that in regions where upper-plate faults are prevalent, strong constraints on fault geometry and slip rate are necessary to disentangle contributions of deeper-seated processes to uplift.

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A new basin depth map of the fault-bound Wellington CBD based on residual gravity anomalies

Stronach

Stern

2021

New Zealand Journal of Geology and Geophysics

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The structure and seismic potential of the Aotea and Evans Bay faults, Wellington, New Zealand

Cited by 5 publications

References 46 publications

Basin effects and limitations of 1D site response analysis from 2D numerical models of the Thorndon basin

Basin effects and limitations of 1D site response analysis from 2D numerical models of the Thorndon basin

Causes of permanent vertical deformation at subduction margins: Evidence from late Pleistocene marine terraces of the southern Hikurangi margin, Aotearoa New Zealand

A new basin depth map of the fault-bound Wellington CBD based on residual gravity anomalies

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