370 Works

Bathymetric map of Lake Rotomahana

Cornel E. J. de Ronde, Fabio Caratori Tontini, S. L. Walker & Jenny Black
This map poster shows a detailed map of the lake floor of Lake Rotomahana at a scale of 1:11 000. As well as the main bathymetric map, there are three smaller maps and two seismic cross sections. These smaller maps show magnetic and heatflow data, and show several hundred locations where plumes of gas bubbles have been recorded. This map shows lake floor features and other subtleties that have not been seen for more than...

Geologic, earthquake and tsunami modelling of the active Cape Egmont Fault Zone

Hannu Seebeck, Glenn P Thrasher, G. P. D. Viskovic, Clarrie Macklin, Suzanne Bull, Xiaoming Wang, Caroline Holden, Yoshihiro Kaneko, V Mouslopoulou & John G. Begg
The Cape Egmont Fault Zone in the southern Taranaki Basin, New Zealand, is a complex series of synthetic and antithetic dip-slip normal faults accommodating present-day extension. The fault zone comprises new and reactivated faults developed over multiple phases of plate boundary deformation during the last 100 Myrs. The fault zone is well imaged on petroleum industry seismic reflection data, with a number of faults exposed and studied onshore. The Cape Egmont Fault Zone is seismically...

New Zealand Community Fault Model - version 1.0

Hannu Seebeck, Russ J. Van Dissen, Nicola J. Litchfield, P. M. Barnes, Andy Nicol, Rob M. Langridge, David J. A. Barrell, Pilar Villamor, Susan M. Ellis & Mark S. Rattenbury
Fault models developed by the scientific community aim to provide a consistent and broadly agreed-upon representation of faults in a region for such societally important endeavours as seismic hazard assessment (e.g. national seismic hazard models), strong ground-motion predictions and physics-based fault systems modelling. The New Zealand Community Fault Model (NZ CFM) is a two- and three-dimensional representation of fault zones associated with the New Zealand plate boundary for which Quaternary activity has been established (or...

New Zealand Paleoseismic Site Database: design and overview of version 1.0

Nicola J. Litchfield, Jade Humphrey, Regine Morgenstern, Robert M. Langridge, Genevieve L. Coffey & Russ J. Van Dissen
The New Zealand Paleoseismic Site Database (new term, new database) contains paleoseismic data (grouped into Slip Rate, Earthquake [EQ] Timings and Recurrence Interval [RI], and Single-Event Displacement [SED]) collected at specific sites along active faults throughout New Zealand. The database was developed as part of the New Zealand National Seismic Hazard Model 2022 Revision Project (NSHM 2022). The primary purpose is to compile paleoseismic data at specific sites to be used either as inputs into,...

ACE Programme – Critical Incident Leadership course learner guide

Hana Craig & Scott Kelly
The seventh batch (2021 intake) of the AHA Centre Executive (ACE) Programme are undertaking the programme online. The Critical Incident Leadership course is one component of the ACE Programme and is facilitated by GNS Science. To deliver the course online, GNS Science will utilise iQualify and Zoom platforms. This document forms a Learner Guide for participants, and sets out the following: Course requirements; Activities needing to be completed before commencing the course; Logging into iQualify,...

West Coast groundwater dynamics and hydrochemical evolution as inferred from regional water age and chemistry tracer data

Magali Moreau, Uwe Morgenstern, Rob W. van der Raaij & J. Horrox
This study aims to holistically describe the flow sources, pathways and lag times of water through the rivers and aquifers of the West Coast catchments. This information is required to ground truth and improve groundwater flow models and management tools. Such improvements will help to prevent degradation of rivers and aquifers from land-use activities that impact on cultural, recreational and economical values, as well as on drinking water supplies and quality. This study is mainly...

Average coseimic slip profiles

Kiran K.S. Thingbaijam, Russ J. Van Dissen, B. E. Shaw & Matt C. Gerstenberger
Despite the potential impact on earthquake rupture forecasts for seismic hazard analysis, derivation of applicable average coseismic slip profiles has received relatively limited attention. Here, we present improved insight using a set of rupture models of past earthquakes. We find that along-strike slip profiles are well approximated by a power-of-sine function with index = 1/2 (i.e. sinesqrt function), corroborating Biasi and Weldon (2006). However, elongated ruptures (with aspect ratios >5.0) have a flatter profile. Additionally,...

Discussion paper of Building Act and Resource Management Act tensions and issues

J Carter, R Evans, B Belgrave, F Beck & K Cook
This report provides a review of how the Building Act 2004 (the Building Act) and the Resource Management Act 1991 (the RMA) work in practise with regard to the management of or response to natural hazards and natural hazard risk. The report reflects an initial high-level scan of potential issues and opportunities and potential overlaps and tensions between the two Acts. (The authors)

Thermal properties of Matahina Ignimbrite

L. McGovern, Fiona Sanders, Michael D. Rosenberg, Anya M. Seward, Isabelle Chambefort & Rob H. Funnell
Thermal properties of a 140 m section of the Matahina Formation ignimbrite were determined from a rock core drilled near Rotorua, New Zealand. For this project, thermal conductivity, thermal diffusivity and specific heat capacity were determined using the divided-bar method in order to investigate interrelationships with density/porosity and lithological variation throughout the unit. Thermal conductivity ranged from 0.25 to 1.44 W/(m.K) for dry samples and 1.06 to 2.18 W/(m.K) for water-saturated samples. Specific heat capacity...

Accounting for earthquake rates’ temporal and spatial variability through least-information Uniform Rate Zone forecasts

P. Iturrieta, Matt C. Gerstenberger, Chris Rollins, Russ J. Van Dissen, T. Wang & D. Schorlemmer
The distribution of earthquakes in time and space is seldom stationary. In low-seismicity regions, non-stationarity and data scarcity may preclude a significant statistical analysis. We investigate the performance of traditional stationary Poisson forecasts (such as smoothed-seismicity models [SSM]), with applications in Probabilistic Seismic Hazard Assessment, in terms of the available training data. We design bootstrap experiments that use multiple pairs of consecutive training-forecast windows of a catalogue to: (i) analyse the lowest available training data...

A simple model of faulting patterns for distributed seismicity in New Zealand

Kiran K.S. Thingbaijam, Mark S. Rattenbury, Russ J. Van Dissen, Matt C. Gerstenberger & John Ristau
We construct a preliminary model of faulting mechanisms, namely the New Zealand Distributed Seismicity Faulting Model, for events with magnitude larger than MW 6.5. This model will complement the distributed seismicity models for shallow (hypocentral depths ≤40 km) crustal earthquakes in New Zealand and inform the 2022 New Zealand National Seismic Hazard Model. Input datasets include the New Zealand Community Fault Model, the New Zealand Active Fault Database and geological map-based fault datasets, and delineations...

2021 New Zealand Ground-Motion Database

Jesse Hutchinson, Brendon A. Bradley, Robin Lee, Liam Wotherspoon, Mike Dupuis, Claudio Schill, Jason Motha, Anna E. Kaiser & Elena F. Manea
This report summarises the development of the 2021 New Zealand ground-motion database. Ground-motion intensity measures have been computed from strong-motion recordings for events with moment (and moment-equivalent) magnitudes equal to or greater than 4.0 from the year 2000 until the end of 2020. These measures include peak ground acceleration, peak ground velocity, cumulative absolute velocity, Arias intensity and pseudo-acceleration response spectra, among others. Along with these intensity measures, we have determined and/or collated earthquake rupture...

Backbone ground-motion models for crustal, interface and slab earthquakes in New Zealand

G. M. Atkinson
A ground-motion model (GMM) that strikes a balance between empirical- and simulation-based approaches is developed in support of the 2022 update of the New Zealand National Seismic Hazard Model. The development follows the backbone approach, comprising a central model to express the median ground motions for earthquakes in New Zealand, along with upper and lower alternatives to describe its epistemic uncertainty. Epistemic uncertainty expresses uncertainty in the median model due to our inability to completely...

Spatial distribution of earthquake occurrence for the New Zealand National Seismic Hazard Model revision

Sepideh J. Rastin, David A. Rhoades, Chris Rollins, Matt C. Gerstenberger, Annemarie Christophersen & Kiran K. S. Thingbaijan
Our goal is to estimate the decadal-to-centurial (~100-year) spatial distribution of earthquake occurrence for the distributed seismicity model of the New Zealand National Seismic Hazard Model (NSHM) update. This report describes the development of candidate models for the spatial seismicity distribution that will need to be assigned to branches of a logic tree to contribute to the distributed seismicity model. Multiplicative hybrid models help us to assess the relative value of different data inputs, including...

Impact of directivity on probabilistic seismic hazard calculations in New Zealand

G. Weatherill
Directivity of ground motion in the near-field region of large earthquakes is a well-observed phenomenon whose impacts can be particularly detrimental to structures that sit close to an earthquake rupture. Predictive models of this phenomenon and its amplifying effect on ground motion have been available for more than 20 years, with recent projects such as the Next Generation Attenuation West 2 (NGA-West2) yielding several advanced models for application in probabilistic seismic hazard analysis (PSHA). Despite...

New Zealand National Seismic Hazard Model 2022 revision : model, hazard and process overview

Matt E. Gerstenberger, Sanjay S. Bora, Brendon A. Bradley, Chris DiCaprio, Russ J. Van Dissen, G. M. Atkinson, Chris Chamberlain, Annemarie Christophersen, Kate J. Clark & Genevieve L. Coffey
The New Zealand National Seismic Hazard Model (NSHM) 2022 revision has involved significant revision of all datasets and model components. In this report, we present a subset of the many results from the model, as well as an overview of the governance, scientific and review processes followed by the NSHM team. The NSHM 2022 models and results are available online, and more extensive results can be found at http://gns.cri.nz/nshm. (The authors)

GeoNet landslide response: Nelson-Tasman District, 16-19 August 2022

Chris I. Massey, Dougal B. Townsend, Kerry Leith, Brenda J. Rosser & Jason Farr
During 16–19 August 2022, an extreme rainfall event affected much of New Zealand. The National Institute of Water & Atmospheric Research (NIWA) refer to this event as the “strongest August atmospheric river (AR) on record” and classified it as a 1-in-120-year rain event for Nelson. The National Emergency Management Agency (NEMA) classified the event as ‘N1’, which elicits a minor national-level response. The rain event triggered many hundreds of landslides and flooding across the Nelson...

Regional fault orientation and length analysis, Aotearoa New Zealand

Mark S. Rattenbury
Over the past few decades, several faults have been identified in Aotearoa New Zealand only because they ruptured in recent damaging earthquakes. The recognition of these previously unidentified earthquake-generating faults has heightened awareness of seismic hazard that extends beyond Aotearoa New Zealand’s large, but still fragmentary, record of known active faults. This has reinforced how important estimating distributed ‘off-fault’ seismicity is for characterising earthquake hazard. To help quantify aspects of distributed seismicity for the National...

Landslide hazard and risk assessment for the Fox and Franz Josef Glacier valleys

Chris I. Massey, Saskia J. de Vilder, T. Taig, Biljana Lukovic, Garth C. Archibald & Regine Morgenstern
This report has been prepared by the Institute of Geological and Nuclear Sciences Limited (GNS Science) for the Department of Conservation (DOC), in response to a request from them for a quantitative assessment of the risk posed by landslides within the Fox and Franz Josef Glacier valleys. The quantitative landslide risk assessment is based on risk-estimation methods that follow appropriate parts of the Australian Geomechanics Society framework for landslide risk management. It provides landslide risk...

Interpretation of Geophysical data from the Eastern margin of the Okataina Volcanic Centre

R. Lithgow, Cecile Massiot, Edward A. Bertrand, Wiebke Heise, Craig A. Miller, Stewart L. Bennie, Thomas Brakenrig, Lauren Coup & Nick Macdonald
The Okataina Volcanic Centre (OVC) is an active caldera complex located in the Taupō Volcanic Zone that has experienced at least four probable caldera collapses since 550 ka. Imaging the shape of the caldera and its margins is important to reconstruct the timing and mechanisms of the successive caldera collapses, and provide the context to interpret monitoring signals of the volcano’s activity. However, topographic margins observable on the surface do not necessarily reflect the major...

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