NSHM - National Seismic Hazard ModelTe Tauira Matapae Pūmate Rū i Aotearoa

NSHM

The National Seismic Hazard Model calculates the likelihood and strength of earthquake shaking that may occur in different parts of Aotearoa New Zealand over specified time periods.

It is critical information, used by government and industry to help improve national resilience and manage risks to safety, security and the economy from seismic events.

Overview 

New Zealand continues to be challenged by earthquakes and, because of our geographical make-up, it always will be. Fortunately, globally, our understanding of earthquake science has improved exponentially. We now know a lot more about earthquake hazard and its impacts than we did previously, so we can prepare better and make good decisions.

An important part of New Zealand’s hazard-scape toolkit, the National Seismic Hazard Model provides an estimate of the likelihood and strength of earthquake ground shaking at any given site in New Zealand and considers how different parts of the country might behave in the event of large magnitude earthquakes. It is part of Aotearoa New Zealand’s science ‘infrastructure’, helping to inform technical standards for earthquake engineering design as well as providing critical information for earthquake risk management relevant to insurance, infrastructure management and emergency planning and response.

Explaining the National Seismic Hazard Model 2022

Explaining the National Seismic Hazard Model 2022

Aotearoa New Zealand sits aside tectonic plates and that puts the country at risk of earthquakes....

The model

The NSHM presents a range of maps, hazard curves and reports that can be used to provide a forecast of the earthquake shaking expected over, for example, the next 10, 50 or 100 years at a range of probability levels.

It is complex science, so we have provided lots of information to help interpret what it means. The following fact sheets, video and regional summaries will help you understand the results.

Ready to view the full NSHM results? Click here(external link).
Otherwise, keep reading to learn more.

Background

The NSHM is world leading science that has been developed and reviewed by many national and international experts. Building the model is complex, a little like building a million-piece puzzle. Scientists study hundreds of thousands of models, almost a million in fact, which all contribute to the final model. The NSHM is very robust, and the science is trusted by the many different decision makers that apply it in their risk assessments.

The 2022 review of the NSHM was led by GNS Science, and funded by MBIE and the Natural Hazards Commission Toka Tū Ake.

GNS Science, MBIE, the Natural Hazards Commission Toka Tū Ake, engineers, universities and other Crown Research Institutes worked together closely on the revision of the model and many local and international scientists and academics have been involved in its development.

GNS Science is the custodian of the NSHM. Key users of the model include MBIE, the Natural Hazards Commission Toka Tū Ake, local and regional authorities, Waka Kotahi NZTA, structural and geotechnical engineers, land-use planners, seismic hazard consultants, risk modelling consultants, and the insurance sector.

What the results tell us

The 2022 revision of the NSHM estimates the likelihood of future earthquake shaking hazard to have increased throughout most of the country, ranging from almost no change to more than doubling in some areas.

On average, results have increased by 50 percent or more from previous modelling, highlighting the need to boost national resilience strategies and readiness.

The NSHM does not describe impact, or assess associated risk. Instead, the model is a science instrument which can be used by government and industry to estimate risk and help make risk-based decisions.  

The 2022 revision of the NSHM shows that seismic hazard has increased almost everywhere throughout Aotearoa New Zealand compared to what we knew previously. This is not unexpected, because:

  • We now know a lot more about earthquake behaviour due to better global understanding, more sophisticated science, and more than a decade of advancements in technical computing. 
  • We now have an improved model of the variability in shaking from potential earthquakes that could rupture in any single location. One significant contributor is the Hikurangi Subduction Zone, another is the Alpine Fault. These are important sources, but we also model the likelihood for earthquakes on unknown (hidden) faults and how shaking can affect regions far from the epicentre.
  •  We can model low probability but potentially high impact events affecting New Zealand, by understanding how faults can link together.


Earthquake hazard varies throughout the country based on the geography and ground conditions in each location, and the frequency and types of earthquakes which might occur.

The NSHM provides multiple results for each location, and they must be considered together to fully understand the hazard. A single aspect of the results considered on its own cannot reflect the level of hazard for a location.

Matt G NSHM GNS Science 31632

NSHM Webinar

Watch the National Seismic Hazard Model webinar to learn more about the science behind the model.

Why we need seismic hazard modelling

Aotearoa New Zealand experiences around 250 felt earthquakes every year (on average) and thousands more are measured. Understanding the likely strength of ground-shaking from future earthquakes is essential for a range of safety, security, resilience, financial, and economic purposes, including to:

  • provide a national assessment of New Zealand’s seismic hazard
  • inform the settings in the Building Code
  • inform the standard for seismic resilience for the development of other infrastructure, such as dams, roads and bridges, through guidance such as the New Zealand Dam Safety Guidelines and Waka Kotahi’s Bridge Manual
  • support risk communication, emergency management, business continuity planning, and community resilience
  • contribute to natural hazard risk and loss models, including those used for insurance and reinsurance purposes, as well as local government resource management and land use planning

This information is essential for New Zealand to build resilience and manage risks to safety, security and the economy from seismic events.

Peter Benfell General Manager Science GNS Science

How the NSHM impacts New Zealanders

The model is used by a variety of end-users to estimate the likely impact of earthquakes on New Zealand land, buildings, infrastructure, and people. It is world-leading science that helps improve our understanding of the impacts of earthquake shaking and allows us to increase our resiliency to earthquake hazard.

The science is the first step. The revised NSHM will be taken into consideration by government and industry, before any decisions and changes are made and brought into policy and practice. Any changes will take time to determine and these will be communicated directly by the responsible agencies.

The update is a joint initiative being led by GNS Science, the Ministry of Business, Innovation and Employment, and the Earthquake Commission. It involves the collective knowledge and skills of a large team of national and international scientists and end-users. The revised NSHM including its component-models and outputs are freely available(external link). 

Building the NSHM

The GNS Science-led National Seismic Hazard Model (NSHM) is a collection of multiple models which together estimate future earthquake shaking in New Zealand. These models represent the broad range of our knowledge (and uncertainty) about how earthquakes occur and how earthquakes cause the surface of the Earth to shake. 

By combining multiple models, the NSHM can incorporate scientific understanding of earthquakes acquired from diverse research fields, ranging from paleoseismology (study of historic earthquakes), geodesy (study of the Earth’s shape and gravity field) and geophysics (study of the physics properties and processes of the Earth), through to engineering seismology (study of earth science and civil engineering to understand seismic hazard).

The NSHM consists of two primary components: 

  • Seismicity rate models: these model potential earthquake sources
  • Ground motion characterisation models: these model how shaking from an earthquake changes as it travels through the Earth’s crust

These components are then combined to estimate ground shaking hazard.

Find out more about the 2010 NSHM

2010 National Seismic Hazard Model

The 2010 National Seismic Hazard Model is the latest revision of the NSHM for New Zealand and was published in 2012. While not considered in the building code, this model has been used in site-specific studies since its publication. 

Research Project Details

Collaborators: GNS Science, University of Canterbury, University of Otago, Auckland University, Geoscience Australia, University of Southern California, UCLA, US Geological Survey, NIWA, Global Earthquake Model (GEM) Foundation, WSP Golder, Missouri University of Science & Technology, Indiana University, Das Deutsche GeoForschungsZentrum (GFZ), Lamont-Doherty Earth Laboratory – Columbia University

Duration

2020 – present

Funding platform

MBIE Building Systems and Performance (BSP), the Natural Hazards Commission Toka Tū Ake

Status

Current

Programme Leader

Dr Matt Gerstenberger

Funder

Ministry of Business, Innovation and Employment (MBIE), the Natural Hazards Commission Toka Tū Ake

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