Hikurangi Subduction Earthquakes & Slip Behaviour

Introduction

Nō te tau, rua mano, tekau mā ono, tae noa atu ki te tau rua mano, e rua tekau mā tahi, ka rangahau tētahi whakaminenga kaipūtaiao nō Aotearoa, nō tāwāhi hoki i te paenga papaneke o Hikurangi kia whai mārama ai i ngā tūraru ka pāngia rānei ki Aotearoa nei. He āinga whakararo te paenga papaneke o Hikurangi nei, ā, kei reira ka āia te papaneke moana o Te Moana-nui-a-Kiwa ki raro tonu i papaneke paparahi o Te Pāpaka-a-Māui. Nā te āinga whakararo e pērā ana ko tētahi momo hapa, ā, he nui ngā rū whenua me ngā tai āniwhaniwha ka hua ake, pērā me Sumatra i te tau rua mano mā whā, pērā me Hiri i te tau rua mano mā tekau, pērā hoki me Hapani i te tau rua mano tekau mā tahi. Ka tauakitia ngā mahi a kaipūtaiao nō Aotearoa e te pūtea nanaiore a Te Hīkina Whakatutuki.

A large team of national and international scientists will be studying the Hikurangi plate boundary to find out what risk it poses to New Zealand. The Hikurangi plate boundary is where the Pacific tectonic plate subducts (or dives underneath) the Australian tectonic plate and is what scientists call a subduction zone.

The Hikurangi subduction zone is poorly understood, yet potentially the largest source of earthquake and tsunami hazard in New Zealand. Subduction zones are a type of fault and are responsible for the largest and most powerful earthquakes and tsunamis in the world, such as Sumatra 2004, Chile 2010, and Japan 2011. We know that the Hikurangi subduction zone can produce large earthquakes and tsunamis, and that these events have occurred in the past. However, we don’t know how often these earthquakes tend to happen, nor do we know how large they can be.

A large component of the project involves building and installing seafloor sensors off the East Coast to detect offshore earthquakes, slow slip events, and reveal New Zealand’s offshore plate tectonic movements for the first time. Similar types of sensors could be used in tsunami and earthquake early warning systems in the future and will create new technological capability for New Zealand. Part of this project provides resources for New Zealand scientists to work on the new data being collected by visiting specialised research ships that carry out drilling and seismic imaging. This data will tell them about the physical conditions and rock types at the plate boundary, and reveal what is causing the Hikurangi subduction zone to move slowly (in slow slip events) or suddenly (in earthquakes). This helps scientists understand what has influenced earthquakes and tsunamis in the past, so they can better anticipate what might happen in the future.

The scientists will also be gathering geological and historical evidence for past large Hikurangi earthquakes to improve our understanding of subduction zone hazards posed to New Zealand. This involves collecting offshore cores and studying coastal sediments to explore the geological record of past earthquake and tsunami events. They will be working with iwi partners to integrate Mātauranga Māori of past Hikurangi earthquakes and tsunami.

The research ship JOIDES resolution is undertaking scientific drilling research from Dec-Jan 2018 and March-May 2018 offshore of the North Island’s East Coast to learn more about the processes that drive large earthquakes and tsunami. We are aware that some people are concerned about the drilling and coring research that is being undertaken and its purpose. The specific region being studied in this expedition is already known to have no potential as a gas hydrate resource, which is part of the reason drilling can proceed safely. New Zealand’s participation in this expedition and in the International Ocean Discovery Programme is supported by Government scientific research funds. We believe the more we understand about what causes these natural hazards to happen, the better we can be prepared.

For more information check out these three project fact sheets:

1. Hikurangi Project Overview Fact Sheet
2. Hikurangi IODP Drilling Fact Sheet
3. Hikurangi Seismic Surveying Fact Sheet

This project finished in September 2021, check out these resources to get the full story:

• Bite-sized Documentary: "1 in 4 chance in the next 50 years" Scientists explain their work on the Hikurangi Subduction Zone
• The Project in Numbers infographic (for a print-quality version, please contact info@eastcoastlab.org.nz)
• Project Timeline Storymap