Historically tide gauge (TG) data have been used to estimate global sea level rise. Critical to the analysis of TG records is the assumption that the TG sites are stable and not affected by vertical land motion (VLM). We analyze century-long TG records from New Zealand that have been affected by VLM due to both major and transient earthquake events at a regional level as well as local instabilities. Using combined GPS and precise leveling, we estimate relative VLM between the GPS and TG of up to 1 mm/year. Based on 15-20 years of GPS data, the effect of seismic activity and slow slip events has uplifted sites by up to 0.8 mm/year on average in Wellington and Dunedin. Updated estimates of long-term relative sea level (RSL) at four New Zealand TGs, as well as an estimate of RSL at a new fifth TG (New Plymouth), are determined using data through 2013-an additional 13 years compared to the previous study. The VLM corrected RSL rates gives our best estimate absolute sea level of +1.45 0.28 mm/year (1891-2013). It is important that absolute sea level derived from RSL rates include realistic estimates of VLM, especially at TG sites that are close to plate boundaries, located in seismically active regions, affected by glacial isostatic adjustment, land ice loss, or gas/oil/water extraction.

The very large and rare Mw ~7.9 Earthquake of 3 May 2006 in the Kingdom of Tonga aroused great interest among both Tongan scientists and their colleagues in Australia, New Zealand, and the United States. To investigate the earthquake we formed a collaborative research group of scientists from Australia, New Zealand, Tonga, and the United States. We brought in seven seismographs from Australia and the US to supplement the three-station network already in Tonga and eight GPS receivers primarily for the islands west of the earthquake epicenter. In addition, we made coastal observations to determine the regional pattern of subsidence associated with the earthquake. The GPS instruments can measure horizontal and vertical motion quite precisely, but only after the earthquake from the time of deployment onward, except for some sites on Tongatapu, Vava’u, and Lifuka that had been occupied by GPS receivers in the past. This report describes our efforts.

We collate nearly two decades of campaign GPS data gathered at over 900 sites throughout New Zealand to release a New Zealand nationwide GPS velocity field. The data span the entire North and South islands of New Zealand with a typical spacing of 10-20 km and a denser network (c. 2-8 km spacing) in the Wellington region, central Taupo Volcanic Zone and parts of the Arthur's Pass area. The dataset provides the most comprehensive-to-date view of crustal deformation within the Australia-Pacific plate boundary zone in the New Zealand region. We discuss the data acquisition, processing and derivation of the velocities and uncertainties. We also undertake corrections for earthquake displacements to obtain a velocity field that is largely representative of interseismic deformation between 1995 and 2013.

The deformation model is a critical component of New Zealand Geodetic Datum 2000 (NZGD2000), the official reference frame for New Zealand. The model is used to manage the relationship between the NZGD2000 and the global International Terrestrial Reference Frame (ITRF), in which precise geodetic measurements are made. Consequently, the deformation model has a direct impact on NZGD2000 coordinates. With improved knowledge of the secular deformation field and models of significant earthquakes to have affected New Zealand since 2000 now being available, the decision was made to update the deformation model. At the same time, the 14-parameter transformation between ITRFs to be used in New Zealand was officially defined.

The Taupo Volcanic Zone (TVZ) is one of the world's most productive regions of rhyolitic volcanism and contains the highly active Okataina Volcanic Centre (OVC). Within the TVZ, intra-arc extension is expressed as normal faulting within a zone known as the Taupo Rift. The OVC is located within a complex part of the rift, where volcanism and deformation is considered influenced by rift structure and kinematics. There has been significant research on the structural, volcanic and geophysical properties of the rift and OVC, but less focus on deformation using geodetic data. The limited studies that have utilized geodetic data do not clearly resolve the distribution of deformation and strain rates within the rift and OVC. This is essential to ensure that deformation signals from volcanic processes at the OVC are correctly identified and distinguished from those related to regional tectonic or local hydrothermal processes within the rift. In this paper, we present a picture of contemporary deformation at the OVC and within the surrounding rift in detail, using existing and new GPS campaign and continuous GPS (cGPS) data collected between 1998 and 2011. The results show a highly heterogeneous deformation and strain rate field (both extension and shortening) through the study area, partitioned into different parts of the rift. Our results agree well with earlier geodetic studies, as well as identify new features, but some deformation patterns conflict with long-term geological observations. In the OVC, we observe a locally rotated horizontal velocity field, significant vertical deformation and variable strain rates across the caldera. In the Tarawera Rift, we identify elevated extension and shear rates, which may have significant implications for volcanism there. A shortening pattern is identified through the central rift, which is unexpected in an intra-arc rifting environment. We attempt to explain the source/s of shortening and extension and discuss their implications for geodetic monitoring efforts in the OVC.

We present a time‐dependent slip model of 12 slow slip events (SSEs) occurring in the Hikurangi margin of New Zealand during 2010 and 2011. This model is obtained by inverting daily GPS solutions from GeoNet's continuous GPS network on the North Island and northern South Island. We compare the properties of these SSEs to observations in Japan, Cascadia, and Mexico and find that Hikurangi SSEs have comparatively large amounts of slip (up to 27 cm), high slip rates (up to 1.4 cm/d), and a large range of depths (10–40 km), durations (7–270 days), and sizes ( M w 5.9–6.9). We further investigate the relationship between the Cape Turnagain SSE and an associated seismic swarm and find that observations are consistent with stress triggering outside the slowly slipping region; however, other explanations cannot be ruled out. We also compare slip during the long‐term Manawatu SSE with the tremor epicenters found by Ide (2012) and note that tremor locations are offset in the downdip direction relative to the slipping region, similar to observations in the Bungo Channel of Japan and Guerrero, Mexico.

We evaluate early postseismic deformation after the 2010 Darfield, New Zealand, earthquake documented by radar satellite interferometry observations. Applying interferometric techniques to TerraSAR-X, COSMO-SkyMed, and ALOS data, we derive evidence for a variety of coupled solid-fluid postseismic processes after the Darfield event. The contractional jog of the Greendale Fault shows a time-dependent subsidence signal during the first ~6 months after the event. We detect a dominant subsidence signal in the epicentral area of the Charing Cross fault and also observe a narrow zone (<; 15km) of right-lateral shear along the eastern end of the Greendale Fault, a likely indication of postseismic afterslip process that is operative there after the event.

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.

A moment magnitude (M-w) 6.2 earthquake struck beneath the outer suburbs of Christchurch, New Zealand's second largest city, on 22 February 2011 local time. The Christchurch earthquake was the deadliest in New Zealand since the 1931 M-w 7.8 Hawkes Bay earthquake and the most expensive in New Zealand's recorded history. The effects of the earthquake on the region's population and infrastructure were severe including 181 fatalities, widespread building damage, liquefaction and landslides. The Christchurch earthquake was an aftershock of the M-w 7.1 Darfield Earthquake of September 2010, occurring towards the eastern edge of the aftershock zone. This was a low recurrence earthquake for New Zealand and occurred on a fault unrecognised prior to the Darfield event. Geodetic and seismological source models show that oblique-reverse slip occurred along a northeast-southwest-striking fault dipping southeast at c. 69 degrees, with maximum slip at 3-4 km depth. Ground motions during the earthquake were unusually large at near-source distances for an earthquake of its size, registering up to 2.2 g (vertical) and 1.7 g (horizontal) near the epicentre and up to 0.8 g (vertical) and 0.7 g (horizontal) in the city centre. Acceleration response spectra exceeded 2500 yr building design codes and estimates based on standard New Zealand models. The earthquake was associated with high apparent stress indicative of a strong fault. Furthermore, rupture in an updip direction towards Christchurch likely led to strong directivity effects in the city. Site effects including long period amplification and near-surface effects also contributed to the severity of ground motions.

We document a sequence of simultaneous short‐term and long‐term slow slip events (SSEs) at the Hikurangi subduction zone during the 2010/2011 period. The sequence of short‐term events (each ∼2–3 weeks in duration) ruptured much of the shallow plate interface (<15 km) at central and northern Hikurangi over a 6‐month period, was accompanied by microseismicity and involved patchy, irregular migration of SSE slip. We suggest that the patchy migration of the short‐term SSE is due to large‐scale (∼100–3500 km2) heterogeneities on the plate interface related to seamount subduction and sediment subduction and/or underplating. This is in contrast to a 2010/2011 long‐term SSE at the central Hikurangi margin, which evolved steadily over ∼1.5 years and ruptured much of the plate interface between 20 and 70 km depth. We suggest that the occurrence of long‐term versus short‐term SSEs at Hikurangi is related to differences in effective normal stresses and relative heterogeneity of the subduction interface. The long‐term SSE sequence began 1 year before the short‐term sequence. Coulomb stress change models suggest that the long‐term SSE may have triggered initiation of the subsequent short‐term SSE sequence. Initiation of the short‐term sequence occurred in a region just updip of or within an interseismically locked portion of the plate interface and may be located within the updip transition from seismic to aseismic behavior. Alternatively, it could be characteristic of a region undergoing partial interseismic coupling. This is in contrast to SSEs observed elsewhere in the world that typically occur within the downdip transition from seismic to aseismic behavior.

On 4 September 2010 a surface‐rupturing crustal earthquake (Mw 7.1) struck the Canterbury Plains region of New Zealand's South Island [Gledhill et al., 2011]. The Canterbury Plains is a region of relatively low seismicity in New Zealand, and the structure that ruptured was a previously unmapped fault (Figure 1a). Fortunately, even though parts of the region experienced liquefaction of unconsolidated sediments and sands—including neighborhoods of the city of Christchurch (population 377,000)—no fatalities occurred. Compared to the average New Zealand aftershock decay model, the aftershock sequence for the 2010 earthquake was relatively underproductive for the first 5 months. But on 22 February 2011 anMw 6.2 aftershock (teleseismic and regional estimates range from (Mw 6.1 to (Mw 6.3 with regional inversions favoring higher values) occurred within kilometers of the center of Christchurch (A. E. Kaiser et al., The (Mw 6.2 Christchurch earthquake of February 2011: Preliminary report, submitted to New Zealand Journal of Geology and Geophysics, 2011). The event increased the productivity of other aftershocks (Figure 1b). This particular aftershock was devastating, generating much more destruction than theMw 7.1 event, including more than 180 fatalities. Recorded peak ground acceleration (PGA) in the city was more than double the acceleration of gravity (g). Many of the poorly consolidated, low‐shear‐wave‐velocity soils liquefied during the shaking. Damage estimates reached approximately US$15 billion, making the aftershock New Zealand's costliest natural disaster.

We undertake detailed near-field numerical modelling of the tsunami generated by the 15 July 2009 earthquake (Mw 7.8) in Fiordland, New Zealand. High resolution bathymetry and topography data at Breaksea and Dusky Sounds, and Chalky and Preservation Inlets are derived mostly from digitised New Zealand nautical charts, Shuttle Radar Topographic Mission (SRTM) 3 arc-second data, and General Bathymetric Chart of the Ocean (GEBCO) 30 s data. A combination of continuous and campaign Global Positioning System (GPS), satellite radar (ALOS/PALSAR InSAR images) and seismology data are used to constrain the seafloor deformation for the initial tsunami condition. This source model, derived independently of DART observations, provides an excellent fit to observed tsunami elevations recorded by DART buoy 55015. The model results in the near field show maximum tsunami elevations in the range 0.5–2.0 m inside the sounds and inlets with maximum flow speeds of 3.0 m/s. Along the open coast, maximum tsunami elevations reach 2.0 m. The high flow speeds through the inlets may change the inlet stratifications and water mass inside the sounds. Media reports and field reconnaissance data show some tsunami evidence at Cormorant Cove, Duck and Goose Coves, and Passage Point.

Research Article| November 01, 2011 Fault Location and Slip Distribution of the 22 February 2011 Mw 6.2 Christchurch, New Zealand, Earthquake from Geodetic Data John Beavan; John Beavan GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) 1GNS Science, Lower Hutt, New Zealand Search for other works by this author on: GSW Google Scholar Eric Fielding; Eric Fielding GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) 2Jet Propulsion Laboratory/Caltech, Pasadena, California, U.S.A. Search for other works by this author on: GSW Google Scholar Mahdi Motagh; Mahdi Motagh GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) 3Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany; also at Department of Geomatics and Surveying Engineering, University of Tehran, Tehran, Iran Search for other works by this author on: GSW Google Scholar Sergey Samsonov; Sergey Samsonov GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) 4European Center for Geodynamics and Seismology, Walferdange, Luxembourg; now at Canada Centre for Remote Sensing, Ottawa, Canada Search for other works by this author on: GSW Google Scholar Nic Donnelly Nic Donnelly GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) 5Land Information New Zealand, Wellington, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information John Beavan 1GNS Science, Lower Hutt, New Zealand GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) Eric Fielding 2Jet Propulsion Laboratory/Caltech, Pasadena, California, U.S.A. GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) Mahdi Motagh 3Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany; also at Department of Geomatics and Surveying Engineering, University of Tehran, Tehran, Iran GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) Sergey Samsonov 4European Center for Geodynamics and Seismology, Walferdange, Luxembourg; now at Canada Centre for Remote Sensing, Ottawa, Canada GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) Nic Donnelly 5Land Information New Zealand, Wellington, New Zealand GNS Science Lower Hutt, New Zealand P. O. Box 30368 Lower Hutt 5040 New Zealand j.beavan@gns.cri.nz (J. B.) Publisher: Seismological Society of America First Online: 09 Mar 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2011 by the Seismological Society of America Seismological Research Letters (2011) 82 (6): 789–799. https://doi.org/10.1785/gssrl.82.6.789 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation John Beavan, Eric Fielding, Mahdi Motagh, Sergey Samsonov, Nic Donnelly; Fault Location and Slip Distribution of the 22 February 2011 Mw 6.2 Christchurch, New Zealand, Earthquake from Geodetic Data. Seismological Research Letters 2011;; 82 (6): 789–799. doi: https://doi.org/10.1785/gssrl.82.6.789 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search The 22 February (local time) MW ∼6.2 Christchurch earthquake occurred within the aftershock region of the 4 September 2010 MW 7.1 Darfield (Canterbury) earthquake (Gledhill et al. 2011). Both the Darfield and Christchurch earthquakes occurred on previously unknown faults in a region of historically low seismicity, but within the zone of plate boundary deformation between the Pacific and Australian plates. The Darfield earthquake caused surface rupture up to 5 m (Quigley et al.2010, forthcoming), but none has been observed associated with the Christchurch earthquake. Geodetic data indicate that strain has been slowly accumulating... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Mw 7.1 Darfield earthquake has provided geologists, geodesists and seismologists with well constrained surface fault rupture extent and displacements, densely spaced GPS coseismic displacements, striking InSAR images, and a globally unprecedented set of near-source strong motion data. Collectively, these datasets indicate that the Darfield earthquake was a complex event, involving rupture of multiple fault planes with most of the earthquake’s moment release resulting from dextral strike-slip movement on the previously unknown, east-west striking, Greendale Fault. They also point to important secondary sources such as a southeast-dipping blind reverse fault near Charing Cross that initiated the rupture sequence, and a northwest-dipping reverse fault near Hororata that increased rupture duration and spatial extent. Although the models are consistent and support each other, this analysis is still preliminary and ongoing research is focused on further integrating these data sets to better understand the nature, extent, depth and timing of sub-events of the Darfield earthquake.

We present a preliminary probabilistic seismic hazard analysis (PSHA) of a site in the Otway basin, Victoria, Australia, as part of the CO2CRC Otway Project for CO2 storage risk. The study involves estimating the likelihood of future strong earthquake shaking at the site and utilizes three datasets: (1) active faults, (2) historical seismicity, and (3) geodetic surface velocities. Our analysis of geodetic data reveals strain rates at the limit of detectability and not significantly different from zero. Consequently, we do not develop a geodetic-based source model for this Otway model.We construct logic trees to capture epistemic uncertainty in both the fault and seismicity source parameters and in the ground-motion prediction. A new feature for seismic hazard modeling in Australia, and rarely dealt with in low-seismicity regions elsewhere, is the treatment of fault episodicity (long-term activity versus inactivity) in our Otway model. Seismic hazard curves for the combined (fault and distributed seismicity) source model show that hazard is generally low, with peak ground acceleration estimates of less than 0.1g at annual probabilities of 10(-3) - 10(-4) = yr. Our preliminary analysis therefore indicates that the site is exposed to a low seismic hazard that is consistent with the intraplate tectonic setting of the region and unlikely to pose a significant hazard for CO2 containment and infrastructure.

We present ground deformation measurements in the Taupo Volcanic Zone (TVZ) using differential interferomeric synthetic aperture radar (DInSAR) observations collected by ALOS PALSAR during 2006-2010, and compare them with displacement observations from continuous GPS. We acquired and processed DInSAR images from two ascending paths (324 and 325) and one descending path (628) covering the TVZ, and produced linear deformation rates and time series of deformation. The DInSAR results were improved by using a modified version of the small baseline subset (SBAS) algorithm that simultaneously solves for deformation rates and residual topographic noise. The accuracy of the DInSAR displacement rates along line-of-sight to the satellite is 0.5-2 cm yr(-1) depending on the number of SAR images and their coherence. We found good agreement between the DInSAR-derived displacement rates and those measured by continuous GPS for the two ascending paths (correlation 0.94 +/- 0.01 and 0.89 +/- 0.02); the DInSAR uncertainties were too large to make a useful comparison for the descending path (correlation 0.66 +/- 0.03). We identified ground deformation due to groundwater and steam extraction for geothermal power. To demonstrate the geophysical application, we modelled the deformation results using simplified sources for some of the geothermal signals using ellipsoidal and tabular approximations.

Double strike: two linked earthquakes caused 2009 South Pacific tsunami The tsunami that struck the Samoan and northern Tongan islands in September 2009 was preceded by a magnitude-8 earthquake on the outer slope of the oceanic trench, where the Pacific plate bends as it enters the subduction zone. This was initially thought to be the sole source of the tsunami, but a more complex picture is emerging. Two groups report the occurrence of two earthquakes, a 'triggered doublet', at nearly the same time and place. What is not clear is which triggered the other. Beavan et al . use an analysis of Global Positioning System station displacements and tsunami models to show that the outer-rise earthquake was accompanied — possibly triggered by — a near-simultaneous mega-thrust earthquake in the adjacent Tonga subduction zone. Lay et al . analyse the available seismic data, and their model suggests that the outer-rise event triggered megathrust faulting. Either way, this dual strike suggests a mechanism for the occasional large tsunamis generated at the Tonga subduction zone.