Wellington, New Zealand
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Beavan J.,Institute of Geological & Nuclear Sciences | Motagh M.,German Research Center for Geosciences | Fielding E.J.,JPL Caltech | Donnelly N.,Land Information New Zealand | Collett D.,Land Information New Zealand
New Zealand Journal of Geology and Geophysics | Year: 2012

We present source models derived from geodetic data for the four major Canterbury earthquakes of 2010-2011. The September 2010 Darfield earthquake was largely right-lateral, but with several other fault segments active. The February 2011 Christchurch earthquake was mixed right-lateral and reverse with a left-stepping offset interrupting an ENE-striking rupture. The June 2011 earthquake included left-lateral slip on a NNW-striking fault. The December 2011 earthquakes were characterised by offshore reverse slip on an ENE-striking plane. Displacements of GPS sites define small but clearly detectable postseismic deformation east of the September 2010 earthquake, near the February 2011 earthquake and following the June 2011 earthquake. There has been no major moment release in a 15-km-long region between the eastern end of the September 2010 faulting and the western end of the February 2011 faulting. We recommend careful monitoring of this region for the next several years. © 2012 The Royal Society of New Zealand.

Petrov L.,NASA | Phillips C.,CSIRO | Tzioumis T.,CSIRO | Stansby B.,Curtin University Australia | And 10 more authors.
Publications of the Astronomical Society of Australia | Year: 2011

We report the results of a successful 7-hour 1.4GHz Very Long Baseline Interferometry (VLBI) experiment using two new stations, ASKAP-29 located in Western Australia and WARK12M located on the North Island of New Zealand. This was the first geodetic VLBI observing session with the participation of these new stations. We have determined the positions of ASKAP-29 and WARK12M. Random errors on position estimates are 150-200 mm for the vertical component and 40-50 mm for the horizontal component. Systematic errors caused by the unmodeled ionosphere path delay may reach 1.3m for the vertical component. © 2011 Astronomical Society of Australia.

News Article | August 22, 2016
Site: www.spie.org

Geodetic discovery of a new magma body beneath New Zealand Magma plays a fundamental role in the formation of new crust on Earth. Along mid-ocean ridge systems, for example, the build-up of stress (caused by the separation of tectonic plates) is relieved through the injection of vertical sheets of magma (known as dikes) during rifting episodes. In addition, at arc and back-arc settings—where subduction of oceanic lithosphere gives rise to magmatism and volcanism—the accumulation of magma helps build new continental crust. In most cases the magma remains at depth, where it eventually cools to form new rock. In rare occasions, however, the material may erupt in very large caldera-forming events or in supereruptions (i.e., when more than 1000km3 of material may be expelled).1 Although rifting episodes and the emplacement of magma beneath oceanic spreading centers is relatively well constrained,2, 3 there are only a few regions in arc and back-arc settings where significant volumes of magma are produced. It is therefore difficult to study the complex interactions between volcanism, tectonics, and magmatism in these settings. Geophysicists can employ a number of techniques to study the geometry, location, and volume of magma being intruded into the Earth's crust. As a result of such intrusions, the surrounding rocks deform and cause small displacements of the ground surface. Geodetic observations, such as from global positioning system (GPS) and satellite radar interferometry (InSAR) measurements, can be used to quantify these displacements. The deformation may also be accompanied by changes in the magnitude and frequency of earthquakes that can be detected by seismology. Furthermore, magnetotelluric (MT) techniques can be used to image the electrically conductive magma bodies. In this study,4 we present geodetic and seismological data from the Taupo Volcanic Zone (TVZ), in New Zealand's North Island, and provide evidence of a new magma body below the surface. The TVZ (see Figure 1) is an active continental rift and arguably the world's most productive region of silicic volcanism.5 Along the TVZ, conductive bodies—imaged at depths of about 6–10km—are thought to be zones of interconnected melt.6 These observations are consistent with geodetic measurements that show widespread subsidence, and which suggest the cooling and contraction of magma within the shallow crust.7 At the northern end of the subaerial TVZ (in the Bay of Plenty region), swarms of earthquakes (see Figure 1) have been detected since the 1970s. The cause of these earthquake swarms, however, has remained largely unresolved. With the use of InSAR and GPS data to measure the surface deformation across the northern TVZ, we have detected an ∼300km2 region of uplift on the edge of the currently active volcanic zone. Both our InSAR and GPS measurements show that the region was undergoing uplift at a rate of about 10mm/year between 2004 and 2011 (see Figure 1). Despite the swarms of earthquakes in the region, the pattern of deformation points toward a magmatic, rather than a tectonic, origin. We have also used a simple elastic model to represent an inflating body of magma and thus determine the source geometry and volume of the detected body. We found that our observations are best explained by the inflation of a horizontal, about 20 × 25km, magmatic body at a depth of 9.5km.4 We also estimate that between 2004 and 2011, 0.06km3 (i.e., 60,000,000m3) of new material was injected into the crust beneath the Bay of Plenty (see Figure 2). Measurements from leveling lines (placed across the region between the 1950s and 1970s), and from other historical geologic data, also provide evidence that the region may have been undergoing uplift for up to about 1700 years. The inflation rate that we have observed during the 2000s, however, is more than double the long-term average. It is unclear whether this was caused by an isolated increase in the melt supply or whether the supply rate has varied with time. The repeated swarms of earthquakes detected in the area seem to indicate the latter option. In fact, a large, well-recorded earthquake swarm (which occurred between 2005 and 2009) was coincident with the observed increase in inflation rate. Our results thus provide evidence that the frequent earthquake swarms in the region occur in response to periodic increases in the magma supply from depth (see Figure 2). In summary, we have used InSAR and GPS data to study the active Taupo Volcanic Zone beneath New Zealand's North Island. Although the ultimate fate of the magma in this region (which contains one of Earth's supervolcanoes) remains unknown, our results provide evidence for the birth of a new magma chamber. In the coming years we hope to expand our investigation with a focused deployment of GPS, MT sensors, and seismometers so that we can probe the size and eruptability of this magma body. We thank the Japan Aerospace Exploration Agency for access to the Advanced Land Observing Satellite data (through project RA4-1093), the European Space Agency for access to the Envisat data (under project C1P-14029), and GeoNet for the continuous GPS data. This work was supported by public research funding from the Government of New Zealand, with additional support from the New Zealand Natural Hazards Research Platform (under grant 2015-GNS-02-NHRP) and Land Information New Zealand.

Stanaway R.,University of New South Wales | Roberts C.,University of New South Wales | Blick G.,Land Information New Zealand
International Association of Geodesy Symposia | Year: 2014

This paper describes a schema for a gridded absolute deformation model (ADM) and non-linear deformation patch model that can be used to transform point positions captured in the International Terrestrial Reference Frame (ITRF), or other closely aligned reference frame, to a reference epoch consistently over time for practical applications. The schema described utilises existing models of rigid plate motion, plate boundary deformation and non-linear deformation (e.g. coseismic and postseismic effects or subsidence). Application of an ADM and patchmodel can enable consistent Precise Point Positioning (PPP) over time and seamless integration of Continuously Operating Reference Station (CORS) networks within deforming zones. The strategy described can also ensure consistency of time-tagged spatial datasets (e.g. laser scanned point clouds and digital cadastral databases) and GIS within a kinematic environment. An ADM can also be used as the basis for static epoch projections of a national or regional kinematic datum. A case study from New Zealand is described. © Springer-Verlag Berlin Heidelberg 2014.

Grant D.B.,RMIT University | Donnelly N.,University of New South Wales | Crook C.,Land Information New Zealand | Amos M.,Land Information New Zealand | And 2 more authors.
Journal of Spatial Science | Year: 2015

In 1995, a dynamic cadastre, based on a dynamic geodetic datum, was proposed for New Zealand to recognise that all cadastral boundaries are in motion. Subsequently New Zealand implemented a semi-dynamic geodetic datum which is accompanied by a deformation model. In 2010 and 2011, the Canterbury region in the South Island of New Zealand was subjected to a sequence of earthquakes that resulted in some boundaries being ruptured by up to 4 metres. A set of localised deformation models was developed to model the seismic movements. The implementation of these models and their accuracy are addressed in this paper. © 2014, © 2014 Mapping Sciences Institute, Australia and Surveying and Spatial Sciences Institute.

Claessens S.J.,Curtin University Australia | Hirt C.,Curtin University Australia | Amos M.J.,Land Information New Zealand | Featherstone W.E.,Curtin University Australia | Kirby J.F.,Curtin University Australia
Survey Review | Year: 2011

The NZGeoid09 gravimetric quasigeoid model of New Zealand was computed through FFT-based Stokesian integration with a deterministically modified kernel and an iterative computation approach that accounts for offsets among New Zealand's 13 different local vertical datums (LVDs). NZGeoid09 is an improvement over the previous NZGeoid05 due to use of the EGM2008 and DNSC08GRA models, and due to improvements to the data processing strategy. The integration parameters of degree of kernel modification L = 40 and cap radius ψ0=2. 5° were determined empirically through a comparison with 1422 GPS/levelling observations, after the LVD offsets had been removed. The precision of NZGeoid09 was assessed using the same GPS/levelling dataset, yielding an overall standard deviation of 6.2 cm. NZGeoid09 performs better than NZGeoid05 and marginally better than EGM2008, but few data are available in the Southern Alps of New Zealand to give a better evaluation. © 2011 Maney Publishing.

Tenzer R.,University of Otago | Vatrt V.,Military Geographic and Hydrometeorogic Office | Amos M.,Land Information New Zealand
International Association of Geodesy Symposia | Year: 2012

We utilize the geopotential value approach to determine the average offsets of 12 major local vertical datums (LVDs) in New Zealand (NZ) relative to the world height system (WHS). The LVD offsets are estimated using the EGM2008 global geopotential model coefficients complete to degree 2159 of spherical harmonics and the GPS-levelling data. WHS is defined by the adopted geoidal geopotential value W0 = 62636856 m2s-2. Our test results reveal that the average offsets of 12 major LVDs situated at the South and North Islands of NZ range from 0.01 m (Wellington 1953 LVD) to 0.37 m (One Tree Point 1964 LVD). The geopotential value of the tide-gauge station used as the origin for the LVD Wellington 1953 is thus almost the same as the geoidal geopotential value W0. EGM2008 and GPS-levelling data are further used to compute the differences between the NZGeoid05 regional quasigeoid model and the EGM2008 global quasigeoid model. The same analysis is done for NZGeoid2009 which is the official national quasigeoid model for NZ. The systematic bias of about 0.56 m is found between NZGeoid05 and EGM2008. A similar systematic bias of about 0.51 m is confirmed between NZGeoid2009 and EGM2008. © Springer-Verlag Berlin Heidelberg 2012.

Gentle P.,Land Information New Zealand | Gledhill K.,Institute of Geological & Nuclear Sciences | Blick G.,Land Information New Zealand
New Zealand Journal of Geology and Geophysics | Year: 2016

New Zealand has a network of approximately 190 Continuously Operating Reference Stations (CORS) operated by GeoNet, is a project housed within GNS Science. The GeoNet continuous GNSS network (cGNSS) includes the 37 stations that make up the Land Information New Zealand (LINZ) PositioNZ network. These stations are run in partnership by the two agencies. The New Zealand CORS stations make a significant contribution to New Zealand's geospatial infrastructure and to international geodesy. Further, the CORS stations have been used to identify more than 25 slow-slip events (SSEs) associated with the Hikurangi subduction zone, play an important role in volcano monitoring and have the potential to identify tsunamigenic earthquakes. This paper will discuss how the two networks were established, how they have evolved since the first stations were established in 1995 and the significant contribution of the late John Beavan. © 2016, © Crown Copyright in the Commonwealth of New Zealand 2016 Land Information New Zealand.

Pearson C.,University of Otago | Crook C.,Land Information New Zealand | Jordan A.,Land Information New Zealand | Denys P.,University of Otago
International Association of Geodesy Symposia | Year: 2016

PositioNZ-PP is an on-line GPS processing utility for New Zealand that is currently being developed by Land InformationNew Zealand (LINZ). The system was developed to process user supplied static GPS data using New Zealand’s PositioNZ CORS network as reference stations. There are already many services like this around the world; however LINZ decided to create its own system to utilize the PositioNZ CORS network and to allow the calculation of coordinates in terms of the NZGD2000 datum. The GPS processing engine incorporates components that check the input RINEX file, identify and acquire RINEX data for the three best PositioNZ stations to act as control, acquire appropriate International GNSS Service (IGS) orbit files and initiate GPS processing. This step generates a set of International Terrestrial Reference Frame (ITRF) coordinates at the epoch of observation, which still must be transformed to the reference epoch of NZGD2000. Because of New Zealand’s location on the Pacific Australian plate boundary, current day models of tectonic deformation are necessary to correct coordinates for tectonic motion that has occurred between the epoch of observation and the reference epoch (2000.0). The PositioNZ-PP system makes use of two subroutines for this purpose. The first (the Station Coordinate Prediction Model) uses parameters determined from a least square analysis of the time series from PositioNZ CORS network to correct coordinates for changes associated with the secular velocity, seasonal (annual and semi-annual) cycles, offsets caused by equipment changes and co-seismic displacements, decaying post-seismic signals and slow-slip events. This subroutine estimates accurate coordinates for the PositioNZ CORS network at the epoch of observation. The second subroutine (the New Zealand Deformation Model) uses a gridded model of the secular velocity field and the co-seismic displacement associated with any relevant earthquakes to transform the coordinates associated with the user data to NZGD2000 at epoch 2000.0. © Springer International Publishing Switzerland 2015.

Blick G.,Land Information New Zealand | Donnelly N.,Land Information New Zealand
New Zealand Journal of Geology and Geophysics | Year: 2016

The geodetic system in New Zealand plays an important role in the development of our country. It comprises intellectual, physical and data components which provide authoritative coordinate systems for New Zealand's areas of territorial and administrative responsibility. Measuring and mapping continues today with the management of our natural and economic resources becoming increasingly dependent on the availability of accurate and consistent spatial information. The foundation of our geographically based datasets, including the cadastral system, is an accurate national geospatial reference system, the ‘geodetic system’. © 2016 The Royal Society of New Zealand.

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