Over the next century, coastal regions are under threat from projected rising sea levels and the potential emergence of groundwater at the land surface (groundwater inundation). The potential economic and social damages of this largely unseen, and often poorly characterised natural hazard are substantial. To support risk-based decision making in response to this emerging hazard, we present a Bayesian modelling framework (or workflow), which maps the spatial distribution of groundwater level uncertainty and inundation under Intergovernmental Panel on Climate Change (IPCC) projections of Sea Level Rise (SLR). Such probabilistic mapping assessments, which explicitly acknowledge the spatial uncertainty of groundwater flow model predictions, and the deep uncertainty of the IPCC-SLR projections themselves, remains challenging for coastal groundwater systems. Our study, therefore, presents a generalisable workflow to support decision makers, that we demonstrate for a case study of a low-lying coastal region in Aotearoa New Zealand. Our results provide posterior predictive distributions of groundwater levels to map susceptibility to the groundwater inundation hazard, according to exceedance of specified model top elevations. We also explore the value of history matching (model calibration) in the context of reducing predictive uncertainty, and the benefits of predicting changes (rather than absolute values) in relation to a decision threshold. The latter may have profound implications for the many at-risk coastal communities and ecosystems, which are typically data poor. We conclude that history matching can indeed increase the spatial confidence of posterior groundwater inundation predictions for the 2030-2050 timeframe.

<p>The low-lying coastal urban area of South Dunedin, New Zealand, is particularly susceptible to the impacts of sea-level rise, which is projected to rise by as much as 1.2 m by 2100 under high emissions scenarios.  Currently, more than 2,500 homes are < 50 cm above mean sea level and groundwater levels are typically < 1 m below the surface.  As sea levels rise, groundwater levels are also predicted to rise, increasing the probability of inland groundwater inundation (groundwater flooding) throughout South Dunedin.  It is therefore imperative to develop an improved understanding of the physical controls, and the uncertainty associated with these controls, on the occurrence and severity of the groundwater inundation hazard caused by rising sea levels.  We deploy a simple and fast-running model within a highly-parametrised Uncertainty Quantification (UQ) workflow to investigate the adequacy of steady-state-only versus transient calibration when assessing the risks of groundwater inundation.  The decision to proceed beyond a steady-state-only calibration is time-consuming and costly (often vastly so) and requires careful attention and further research in practical application.  The reduction in uncertainty of decision-relevant forecasts accrued through implementing a transient calibration procedure (or lack thereof), given existing and yet to be acquired data, is the metric by which the modelling is judged.  Firstly, the workflow involves history matching and uncertainty analysis implemented through PESTPP-IES to explore and reduce the uncertainty of decision-relevant forecasts (spatial groundwater elevation and drain fluxes).  Secondly, a paired complex-simple model analysis is used to: explore 1) the potential uncertainty reductions in decision-relevant forecasts achieved through transient calibration and 2) the potential introduction of unquantifiable bias of decision-relevant forecasts introduced by the competing calibration procedures.</p>

Türangawaewae is one of the most well-known and powerful Mäori concepts. 1As türanga means "standing place, " and waewae "the feet, " it is most commonly translated as "a place to stand." 2 But simple translation misses a deeper spiritual meaning.Türangawaewae are places where we feel connected and empowered. 3They are our foundation, our place in the world, our home.Connection to place and the whenua (land) is fundamental to Mäori identity, and not unfamiliar to Päkehä.It shapes our thinking, our way of being, our priorities and values.Connection to the land is a familiar concept for earth scientists, as it forms a large part of their daily lives and is often a raison d'être for their work.After more than three decades mapping geology and observing landscapes, the way in which Simon Cox (Principal Scientist, GNS Science) understands and 'reads' the landscape has gradually evolved.While he was initially trained to see a static, old and 'timeless land' of hard rocks and deep geological time, New Zealand's active tectonics and natural hazard events have shown Simon a more dynamic, lively and dramatic set of processes that continue to shape Papatüänuku (mother earth).

ABSTRACTA probabilistic model for earthquake-induced persistent groundwater-level response as a function of peak ground velocity (PGV) has been constructed using a catalog of monitoring well observations spanning multiple earthquakes. The regional-scale, multi-site, multi-earthquake investigation addresses the occurrence and absence of hydraulic responses to large earthquakes spanning almost a decade of seismic shaking. Persistent groundwater-level changes, or absences of change, have been quantified in 495 monitoring wells in response to one or more of 11 recent New Zealand earthquakes larger than Mw 5.4 that occurred between 2008 and 2017. A binary logistic regression model with random effects has been applied to the dataset using three predictors: earthquake shaking (PGV), degree of hydrogeological confinement (monitoring well depth), and rock strength (site-average shear-wave velocity). Random effects were included as a partial proxy for variations in monitoring wells’ susceptibilities to earthquake-induced persistent water-level changes. Marginal probabilities have been calculated as a function of PGV and related to modified Mercalli intensity (MMI) levels using a New Zealand-specific MMI–PGV relationship that enables the likelihood of persistent water-level changes to be expressed for MMIs of II–VIII. This study capitalizes on one of the largest catalogs of earthquake hydrological observations compiled worldwide and is the first attempt at incorporating seismic and hydrogeological factors in a common probabilistic description of earthquake-induced groundwater-level changes. This modeling framework provides a more generalizable approach to quantifying responses than alternative metrics based on epicentral distance, magnitude, and seismic energy density. It has potential to enable better comparison of international studies and to inform practitioners making engineering or investment decisions to mitigate risk and increase the resilience of water-supply infrastructure.

©2019. American Geophysical Union. All Rights Reserved. Earthquakes have been inferred to induce hydrological changes in aquifers on the basis of either changes to well water-levels or tidal behavior, but the relationship between these changes remains unclear. Here, changes in tidal behavior and water-levels are quantified using a hydrological network monitoring gravel aquifers in Canterbury, New Zealand, in response to nine earthquakes (of magnitudes M w 5.4 to 7.8) that occurred between 2008 and 2015. Of the 161 wells analyzed, only 35 contain water-level fluctuations associated with “Earth + Ocean” (7) or “Ocean” (28) tides. Permeability reduction manifest as changes in tidal behavior and increased water-levels in the near field of the Canterbury earthquake sequence of 2010–2011 support the hypothesis of shear-induced consolidation. However, tidal behavior and water-level changes rarely occurred simultaneously (~2%). Water-level changes that occurred with no change in tidal behavior reequilibrated at a new postseismic level more quickly (on timescales of ~50 min) than when a change in tidal behavior occurred (~240 min to 10 days). Water-level changes were more than likely to occur above a peak dynamic stress of ~50 kPa and were more than likely to not occur below ~10 kPa. The minimum peak dynamic stress required for a tidal behavior change to occur was ~0.2 to 100 kPa.

© 2019 K. C. Weaver et al. The 2016 Mw 7.8 Kaikōura earthquake induced groundwater level changes throughout New Zealand. Water level changes were recorded at 433 sites in compositionally diverse, young, shallow aquifers, at distances of between 4 and 850 km from the earthquake epicentre. Water level changes are inconsistent with static stress changes but do correlate with peak ground acceleration (PGA). At PGAs exceeding 2 m/s2, water level changes were predominantly persistent increases. At lower PGAs, there were approximately equal numbers of persistent water level increases and decreases. Shear-induced consolidation is interpreted to be the predominant mechanism causing groundwater changes at accelerations exceeding 2 m/s2, whereas permeability enhancement is interpreted to predominate at lower levels of ground acceleration. Water level changes occur more frequently north of the epicentre, as a result of the fault's northward rupture and resulting directivity effects. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.

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The 14 November 2016 Mw 7.8 Kaikoura earthquake generated more than 10,000 landslides over a total area of about 10,000 km(2), with the majority concentrated in a smaller area of about 3600 km(2). The largest landslide triggered by the earthquake had an approximate volume of 20(+/- 2) M m3, with a runout distance of about 2.7 km, forming a dam on the Hapuku River. In this article, we present version 1.0 of the landslide inventory we have created for this event. We use the inventory presented in this article to identify and discuss some of the controls on the spatial distribution of landslides triggered by the Kaikoura earthquake. Our main findings are (1) the number of medium to large landslides (source area >= 10,000 m(2)) triggered by the Kaikoura earthquake is smaller than for similar-sized landslides triggered by similar magnitude earthquakes in New Zealand; (2) seven of the largest eight landslides (from 5 to 20 M m(3)) occurred on faults that ruptured to the surface during the earthquake; (3) the average landslide density within 200 m of a mapped surface fault rupture is three times that at a distance of 2500 m or more from a mapped surface fault rupture; (4) the "distance to fault" predictor variable, when used as a proxy for ground-motion intensity, and when combined with slope angle, geology, and elevation variables, has more power in predicting landslide probability than the modeled peak ground acceleration or peak ground velocity; and (5) for the same slope angles, the coastal slopes have landslide point densities that are an order of magnitude greater than those in similar materials on the inland slopes, but their source areas are significantly smaller.

The MW 7.1 Darfield (Canterbury) earthquake, 4 September 2010, generated widespread hydrological effects in New Zealand ranging from instantaneous changes of piezometric levels, to more sustained postseismic changes in spring flow, river discharge and groundwater levels, and increased turbidity and declined yields of water abstracted from wells. Four years later, piezometric levels remained elevated in deeper (>40 m) aquifers along the north‐western (upper) side of the Canterbury Plains near the Greendale Fault, with changes in mean piezometric level reaching +13 m. Linear reservoir modeling (eigen modeling) suggests that sustained high groundwater was not the result of changes in abstraction or land surface recharge. Step‐drawdown tests at six wells within 15 km of Greendale Fault were carried out prior to the earthquake and were retested following fault rupture. Eden‐Hazel analysis of discharge/drawdown relationships discriminates potential sources of head losses, and how these changed (or otherwise) as a result of the earthquake. Objective application of Eden‐Hazel analysis provided confidence levels for the interpretation, including when step tests provide reliable/unreliable estimates of transmissivity change. Increases in both aquifer losses and well losses were observed in four wells, reflecting both a change in sediment transmissivity and decrease in well efficiency. At two locations, the data were unable to provide results that can be interpreted with confidence. As the majority of local groundwater flow occurs through high‐permeability open framework gravel lenses, we suggest that reduction in the permeability of these gravels, due to fine‐sediment incursion, is the cause of the reduction in transmissivity and increase in well losses.

The Southern Alps orogen of New Zealand results from late Cenozoic convergence between the Indo-Australian and Pacific plates and is one of the most active mountain belts in the world. Metamorphic rocks carrying a polymetamorphic legacy, ranging from low-greenschist to high-grade amphibolites, are exhumed in the hanging wall of the Alpine Fault. On a regional scale, the metamorphic grade has previously been described in terms of metamorphic zones and mineral isograds; application of quantitative petrology being severely limited owing to unfavorable quartzofeldspathic lithologies. This study quantifies peak metamorphic temperatures (T) in a 300×20km area, based on samples forming 13 transects along-strike from Haast in the south to Hokitika in the north, using thermometry based on Raman spectroscopy of carbonaceous material (RSCM). Peak metamorphic T decreases across each transect from ≥640°C locally in the direct vicinity of the Alpine Fault to less than 330°C at the drainage divide 15–20km southeast of the fault. Thermal field gradients exhibit a degree of similarity from the southernmost to the northernmost transects, are greater in low-grade semischist than high-grade schist, are affected by folding or discontinuous juxtaposition of metamorphic zones, and contain limited information on crustal-scale geothermal gradients. Temperatures derived by RSCM thermometry are slightly (≤50°C) higher than those derived by traditional quantitative petrology using garnet–biotite thermometry and THERMOCALC modeling. The age of RSCM T appears to be mostly pre-Cenozoic over most of the area except in central Southern Alps (Franz Josef–Fox area), where the amphibolite facies schists have T of likely Cenozoic age. The RSCM T data place some constraints on the mode of exhumation along the Alpine Fault and have implications for models of Southern Alps tectonics.

Magnetic properties of sedimentary strata recovered in Antarctic drill-cores from southern McMurdo Sound have been used to deduce climatic processes, but interpretation is limited by lack of information regarding the magnetic mineralogy of potential source rocks. Here we assess the magnetic mineralogy, concentration and grain size of magnetic remanence carriers in exposed rocks of southern Victoria Land and evaluate their potential contribution to Holocene-modern sediments. Modern sediments contain high concentrations of Ti-magnetite likely derived from the McMurdo Volcanic Group and minor concentrations of high-coercivity minerals, possibly derived from the Skelton Group and Beacon Supergroup. Significant quantities of superparamagnetic grains are present in all cover sediments, which were probably generated through glacial (grinding) processes or during sediment transport. We suggest that modern, hyper-arid conditions in southern Victoria Land prevent alteration of superparamagnetic grains and that they may be a useful proxy for the modern climate state.

River bedload surveyed at 50 sites in Westland is dominated by Alpine Schist or Torlesse Greywacke from the Alpine Fault hanging wall, with subordinate Pounamu Ultramafics or footwall-derived Western Province rocks. Tumbling experiments found ultramafics to have the lowest attrition rates, compared with greywacke sandstone and granite (which abrade to produce silt to medium-sand), or incompetent schist (which fragments). Arahura has greater total concentrations (103–105 t/km2) and proportions (5–40%) of ultramafic bedload compared with Hokitika and Taramakau catchments (101–104 t/km2, mostly <10%), matching relative areas of mapped Pounamu Ultramafic bedrock, but enriched relative to absolute areal proportions. Western Province rocks downthrown by the Alpine Fault are under-represented in the bedload. Enriched concentrations of ultramafic bedload decrease rapidly with distance downstream from source rock outcrops, changing near prominent ice-limit moraines. Bedload evolution with transport involves both downstream fining and dilution from tributaries, in a sediment supply regime more strongly influenced by tectonics and the imprint of past glaciation. Treasured New Zealand pounamu (jade) is associated with ultramafic rocks. Chances of discovery vary between catchments, are increased near glacial moraines, and are highest near source-rock outcrops in remote mountain headwaters.

A large rock avalanche fell from the slope below Hillary Ridge of Aoraki/Mount Cook at 21:32 (New Zealand Standard Time (NZST) = UTC + 12 h) on Monday 14 July 2014. About 0.9 million m3 of indurated greywacke collapsed from a >60° slope at 43.6165°S 170.1427°E between 2600 and 2920 m, without warning or apparent trigger. The avalanche of rock debris crossed Noeline Glacier névé, entraining snow and ice debris, before passing through an icefall, accelerating down steepening slopes and ended on Hooker Glacier. A small mountaineering shelter sited on a topographic high within the avalanche path was damaged but not completely destroyed. Covering a total fall of 1600 m and travel distance of 3.9 km, the avalanche angle of reach was 24°. The deposit of rock, snow and ice debris covers 1.4 million m2. Airborne dust travelled at least 6 km. The event was recorded by the national seismograph network, as a ML2.6 earthquake with the strongly emergent characteristics of a large avalanche.

Thermal springs in the Southern Alps, New Zealand, originate through penetration of fluids into a thermal anomaly generated by rapid uplift and exhumation on the Alpine Fault. Copland hot spring (43.629S, 169.946E) is one of the most vigorously flowing, hottest of the springs, discharging strongly effervescent CO2-rich 56-58 degrees C water at 6 +/- 1lsec(-1). Shaking from the Mw7.8 Dusky Sound (Fiordland) 2009 and Mw7.1 Darfield (Canterbury) 2010 earthquakes, 350 and 180km from the spring, respectively, resulted in a characteristic approximately 1 degrees C delayed cooling over 5days. A decrease in conductivity and increase in pH were measured following the Mw7.1 Darfield earthquake. Earthquake-induced decreases in Cl, Li, B, Na, K, Sr and Ba concentrations and an increase in SO4 concentration reflect higher proportions of shallow-circulating meteoric fluid mixing in the subsurface. Shaking at amplitudes of approximately 0.5% g Peak Ground Acceleration (PGA) and/or 0.05-0.10MPa dynamic stress influences Copland hot spring temperature, which did not respond during the Mw6.3 Christchurch 2011 aftershock or other minor earthquakes. Such thresholds should be exceeded every 1-10years in the central Southern Alps. The characteristic cooling response at low shaking intensities (MM III-IV) and seismic energy densities (approximately 10(-1)Jm(-3)) from intermediate-field distances was independent of variations in spectral frequency, without the need for post-seismic recovery. Observed temperature and fluid chemistry responses are inferred to reflect subtle changes in the fracture permeability of schist mountains adjacent to the spring. Permanent 10(-7)-10(-6) strains recorded by cGPS reflect opening or generation of fractures, allowing greater quantities of relatively cool near-surface groundwater to mix with upwelling hot water. Active deformation, tectonic and topographic stress in the Alpine Fault hanging wall, where orographic rainfall, uplift and erosion are extreme, make the Southern Alps hydrothermal system particularly susceptible to earthquake-induced transient permeability.

Active fault traces are a surface expression of permanent deformation that accommodates the motion within and between adjacent tectonic plates. We present an updated national-scale model for active faulting in New Zealand, summarize the current understanding of fault kinematics in 15 tectonic domains, and undertake some brief kinematic analysis including comparison of fault slip rates with GPS velocities. The model contains 635 simplified faults with tabulated parameters of their attitude (dip and dip-direction) and kinematics (sense of movement and rake of slip vector), net slip rate and a quality code. Fault density and slip rates are, as expected, highest along the central plate boundary zone, but the model is undoubtedly incomplete, particularly in rapidly eroding mountainous areas and submarine areas with limited data. The active fault data presented are of value to a range of kinematic, active fault and seismic hazard studies.

We formally introduce 14 new high-level stratigraphic names to augment existing names and to hierarchically organise all of New Zealand's onland and offshore Cambrian-Holocene rocks and unconsolidated deposits. The two highest-level units are Austral Superprovince (new) and Zealandia Megasequence (new). These encompass all stratigraphic units of the country's Cambrian-Early Cretaceous basement rocks and Late Cretaceous-Holocene cover rocks and sediments, respectively. Most high-level constituents of the Austral Superprovince are in current and common usage: Eastern and Western Provinces consist of 12 tectonostratigraphic terranes, 10 igneous suites, 5 batholiths and Haast Schist. Ferrar, Tarpaulin and Jaquiery suites (new) have been added to existing plutonic suites to describe all known compositional variation in the Tuhua Intrusives. Zealandia Megasequence consists of five predominantly sedimentary, partly unconformity-bounded units and one igneous unit. Momotu and Haerenga supergroups (new) comprise lowermost rift to passive margin (terrestrial to marine transgressive) rock units. Waka Supergroup (new) includes rocks related to maximum marine flooding linked to passive margin culmination in the east and onset of new tectonic subsidence in the west. Maui and Pakihi supergroups (new) comprise marine to terrestrial regressive rock and sediment units deposited during Neogene plate convergence. Ruaumoko Volcanic Region (new) is introduced to include all igneous rocks of the Zealandia Megasequence and contains the geochemically differentiated Whakaari, Horomaka and Te Raupua supersuites (new). Our new scheme, Litho2014, provides a complete, high-level stratigraphic classification for the continental crust of the New Zealand region.