scholarly journals Geophysical Constraints on the Relationship Between Seamount Subduction, Slow Slip, and Tremor at the North Hikurangi Subduction Zone, New Zealand

2018 ◽  
Vol 45 (23) ◽  
Author(s):  
Daniel H. N. Barker ◽  
Stuart Henrys ◽  
Fabio Caratori Tontini ◽  
Philip M. Barnes ◽  
Dan Bassett ◽  
...  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
Slow Slip ◽  
The North ◽  
Seamount Subduction ◽  
The Relationship

Slow Slip Events in New Zealand

2020 ◽  
Vol 48 (1) ◽  
pp. 175-203 ◽  
Author(s):  
Laura M. Wallace
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
Slow Motion ◽  
Plate Motion ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Diverse Range ◽  
The North ◽  
Interseismic Coupling ◽  
Natural Laboratory

Continuously operating global positioning system sites in the North Island of New Zealand have revealed a diverse range of slow motion earthquakes on the Hikurangi subduction zone. These slow slip events (SSEs) exhibit diverse characteristics, from shallow (<15 km), short (<1 month), frequent (every 1–2 years) events in the northern part of the subduction zone to deep (>30 km), long (>1 year), less frequent (approximately every 5 years) SSEs in the southern part of the subduction zone. Hikurangi SSEs show intriguing relationships to interseismic coupling, seismicity, and tectonic tremor, and they exhibit a diversity of interactions with large, regional earthquakes. Due to the marked along-strike variations in Hikurangi SSE characteristics, which coincide with changes in physical characteristics of the subduction margin, the Hikurangi subduction zone presents a globally unique natural laboratory to resolve outstanding questions regarding the origin of episodic, slow fault slip behavior. ▪  New Zealand's Hikurangi subduction zone hosts slow slip events with a diverse range of depth, size, duration, and recurrence characteristics. ▪  Hikurangi slow slip events show intriguing relationships with seismicity ranging from small earthquakes and tremor to larger earthquakes. ▪  Slow slip events play a major role in the accommodation of plate motion at the Hikurangi subduction zone. ▪  Many aspects of the Hikurangi subduction zone make it an ideal natural laboratory to resolve the physical processes controlling slow slip.

Geodetic strain and the deformational history of the North Island of New Zealand during the late Cainozoic

1987 ◽  
Vol 321 (1557) ◽  
pp. 163-181 ◽  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Late Quaternary ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Metamorphic Belt ◽  
Volcanic Region ◽  
The North ◽  
Plate Boundary Zone

The subduction zone under the east coast of the North Island of New Zealand comprises, from east to west, a frontal wedge, a fore-arc basin, uplifted basement forming the arc and the Central Volcanic Region. Reconstructions of the plate boundary zone for the Cainozoic from seafloor spreading data require the fore-arc basin to have rotated through 60° in the last 20 Ma which is confirmed by palaeomagnetic declination studies. Estimates of shear strain from geodetic data show that the fore-arc basin is rotating today and that it is under extension in the direction normal to the trend of the plate boundary zone. The extension is apparently achieved by normal faulting. Estimates of the amount of sediments accreted to the subduction zone exceed the volume of the frontal wedge: underplating by the excess sediments is suggested to be the cause of late Quaternary uplift of the fore-arc basin. Low-temperature—high-pressure metamorphism may therefore be occurring at depth on the east coast and high-temperature—low-pressure metamorphism is probable in the Central Volcanic Region. The North Island of New Zealand is therefore a likely setting for a paired metamorphic belt in the making.

scholarly journals Slow slip near the trench at the Hikurangi subduction zone, New Zealand

Science ◽  
2016 ◽  
Vol 352 (6286) ◽  
pp. 701-704 ◽  
Author(s):  
L. M. Wallace ◽  
S. C. Webb ◽  
Y. Ito ◽  
K. Mochizuki ◽  
R. Hino ◽  
...  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
Slow Slip

scholarly journals A preliminary catalogue of Hikurangi, New Zealand, Slow Slip Earthquakes, from January 2000 to February 2014

2021 ◽  
Author(s):  
◽  
B. Peter Baxter
Keyword(s):  
New Zealand ◽  
Temporal Evolution ◽  
Processing Route ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Slip Rates ◽  
The North ◽  
General Terms ◽  
Significant Step

<p>This thesis documents processing carried out on cGPS data from 115 sites in the North Island and the top of the South Island of New Zealand in order to produce a catalogue of slow slip events (SSEs) for the Hikurangi Margin covering the period Jan 2000 to Feb 2014. It covers the background to the concept of SSEs and the reporting to date on their occurrence along the Margin, the methods used in the processing and analysis, the results of each significant step, and discussion of the results.  It has been shown that the processing route adopted in this work has reduced the average noise levels in the cGPS data by up to 67%, and has eliminated virtually all correlated (“pink”) noise, thus enabling the detection of small-amplitude events (~ 2mm in cGPS signals).  One hundred and fifty events are catalogued in total, of which 137 are considered likely to be SSEs or similar. The catalogue includes estimates of the uncertainty in each parameter and is thus considered the most comprehensive to date. Sixteen of the inversion results were able to be directly compared with published information and showed satisfactory agreement on location and equivalent moment magnitudes.  The important aspects of the project that have been developed further than has been documented to date in the literature include: partitioning of the secular velocity field over the margin to allow the underlying tectonic signal to be better understood; detailed characterization of the temporal evolution of the SSEs; the identification of approximately 40 events that show slips in the opposite direction to that expected; and some preliminary conclusions concerning event scaling.  One of the objectives of the project was to identify whether there were fundamental differences in the characteristics of SSEs in the northeast and southwest of the margin. On the basis of the analyses to date, it appears that the events form a continuum, at least in terms of depth, temporal evolution, source slip rates and scaling, but in general terms the events in the southwest have been confirmed to be of longer duration than those in the northeast.  The project has identified further work that needs to be carried out or is ongoing in order to maximize the value of these new results.</p>

scholarly journals Adjoint tomography of the Hikurangi subduction zone and the North Island of New Zealand

2021 ◽  
Author(s):  
Bryant Chow
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Plate Boundary ◽  
Velocity Model ◽  
Seismic Velocities ◽  
Low Velocity ◽  
Velocity Models ◽  
The North ◽  
Adjoint Tomography

<p><b>Seismic tomography is a powerful tool for understanding Earth structure. In New Zealand, velocity models derived using ray-based tomography have been used extensively to characterize the complex plate boundary between the Australian and Pacific plates. Advances in computational capabilities now allow us to improve these velocity models using adjoint tomography, an imaging method which minimizes differences between observed and simulated seismic waveforms. We undertake the first application of adjoint tomography in New Zealand to improve a ray-based New Zealand velocity model containing the Hikurangi subduction zone and the North Island of New Zealand.</b></p> <p>In support of this work we deployed the Broadband East Coast Network (BEACON), a temporary seismic network aimed at improving coverage of the New Zealand permanent network, along the east coast of the North Island. We concurrently develop an automated, open-source workflow for full-waveform inversion using spectral element and adjoint methods. We employ this tool to assess a candidate velocity model’s suitability for adjoint tomography. Using a 3D ray-based traveltime tomography model of New Zealand, we generate synthetic seismic waveforms for more than 10 000 source–receiver pairs and evaluate waveform misfits. We subsequently perform synthetic checkerboard inversions with a realistic New Zealand source–receiver distribution. Reasonable systematic time shifts and satisfactory checkerboard resolution in synthetic inversions indicate that the candidate model is appropriate as an initial model for adjoint tomography. This assessment also demonstrates the relative ease of use and reliability of the automated tools.</p> <p>We then undertake a large-scale adjoint tomography inversion for the North Island of New Zealand using up to 1 800 unique source–receiver pairs to fit waveforms with periods 4–30 s, relating to minimum waveform sensitivities on the order of 5 km. Overall, 60 geographically well-distributed earthquakes and as many as 88 broadband station locations are included. Using a nonlinear optimization algorithm, we undertake 28 model updates of Vp and Vs over six distinct inversion legs which progressively increase resolution. The total inversion incurred a computational cost of approximately 500 000 CPU-hours. The overall time shift between observed and synthetic seismograms is reduced, and updated velocities show as much as ±30% change with respect to initial values. A formal resolution analysis using point spread tests highlights that velocity changes are strongly resolved onland and directly offshore, at depths above 30 km, with low-amplitude changes (> 1%) observed down to 100 km depth. The most striking velocity changes coincide with areas related to the active Hikurangi subduction zone.</p> <p>We interpret the updated velocity model in terms of New Zealand tectonics and geology, and observe good agreement with known basement terranes, and major structural elements such as faults, sedimentary basins, broad-scale subduction related features. We recover increased spatial heterogeneity in seismic velocities along the strike of the Hikurangi subduction zone with respect to the initial model. Below the East Coast, we interpret two localized high-velocity anomalies as previously unidentified subducted seamounts. We corroborate this interpretation with other work, and discuss the implications of deeply subducted seamounts on slip behavior along the Hikurangi margin. In the Cook Strait we observe a low-velocity zone that we interpret as a deep sedimentary basin. Strong velocity gradients bounding this low-velocity zone support hypotheses of a structural boundary here separating the North and South Islands of New Zealand. In the central North Island, low-velocity anomalies are linked to surface geology, and we relate seismic velocities at depth to crustal magmatic activity below the Taupo Volcanic Zone.</p> <p>This new velocity model provides more accurate synthetic seismograms and additional constraints on enigmatic tectonic processes related to the North Island of New Zealand. Both the velocity model itself, and the underpinning methodological contributions, improve our ever-expanding understanding of the North Island of New Zealand, the Hikurangi subduction zone, and the broader Australian-Pacific plate boundary.</p>

Three‐Dimensional Modeling of Spontaneous and Triggered Slow‐Slip Events at the Hikurangi Subduction Zone, New Zealand

2019 ◽  
Vol 124 (12) ◽  
pp. 13250-13268 ◽  
Author(s):  
Bunichiro Shibazaki ◽  
Laura M. Wallace ◽  
Yoshihiro Kaneko ◽  
Ian Hamling ◽  
Yoshihiro Ito ◽  
...  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
Three Dimensional ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling
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