Sign In
New Zealand
News release
From:
CT scans help uncover Waikato’s earthquake activity on hidden faults
19 February 2026 – In a world-first use of medical imaging technology, scientists have revealed the earthquake-generating potential of faults in the Hamilton and Hauraki areas.
Published today [19 February 2026], the study shows that hidden geological faults in Hamilton city, and newly studied faults in the Hauraki district, are capable of generating moderate to large earthquakes, and have done so in the past 15,700 years.
A new liquefaction analysis technique involving multiple lake sediment cores has strong potential for use in other seismically and volcanically active regions, with the ability to detect large prehistoric earthquakes even when the faults that generated them are completely buried.
Use of medical CT technology
The multidisciplinary research team used 3D CT scanning to examine sediment cores extracted from 20,000-year-old lakes scattered throughout the Hamilton Basin.
Sediment cores – tubes of organic-rich mud carefully removed so any layering remains intact – were scanned to reveal distinctive deformation features known as tephra seismites: layers of volcanic ash liquefied during strong earthquakes.
CT imaging allowed the seismites to be viewed in their entirety and their dimensions accurately measured, from which a new method of evaluating the earthquake history was developed.
For the first time, researchers provided evidence that at least four active faults in the wider Hamilton-Hauraki area have produced at least five earthquakes over the past 15,700 years. Three of these earthquakes had magnitudes of 7 or greater, with two occurring within the past 1,800 years.
The identified faults include the hidden Kūkūtāruhe and Te Tātua ō Wairere faults in the Hamilton lowlands and the Te Puninga and Kerepehi faults in the Hauraki Plains. The data also suggest a previously unrecognised fault occurs near Te Awamutu.
University of Waikato Emeritus Professor David Lowe says the lake-preserved tephra seismites act like natural seismographs, revealing past quakes and hidden risks.
“Using our new approach, we can detect and date large prehistoric earthquakes even when the faults themselves are completely buried. The known ages on the ash layers allowed us to work out when the earthquakes occurred,” Professor Lowe says.
New science with global potential
The research marks the first time the prehistoric earthquake history of the Hamilton Basin has been revealed.
Professor Lowe says radiographer Nic Ross from I-MED Hamilton Radiology worked with the team to scan 161 sediment cores from 18 lakes, placing them onto a CT scanner bed to generate digital images.
“Our analysis of the cores and scans showed where the strongest ground shaking occurred and allowed us to identify which fault ruptured and when,” he says.
Three of the four identified faults ruptured at least once.
The new technique has strong potential for use in other seismically and volcanically active regions, including Auckland, Taranaki–Whanganui, Hawke’s Bay, and internationally in places such as Iceland, Japan, northwestern USA, and central-eastern Europe.
Improving long-term earthquake planning
While Waikato remains a low-to-moderate seismic risk region, the study confirms that strong shaking is possible.
“This doesn’t mean the short-term earthquake risk has increased,” Professor Lowe says. “But it does mean we now understand the long-term hazard much better, and that knowledge helps communities plan, particularly for critical infrastructure such as hospitals, power facilities, and transport networks.
“We haven't changed the hazard since the faults were first discovered in 2015 – we just know more about it. The probability of a large earthquake is relatively low by New Zealand standards, but it is not zero, and risk increases as populations and development expand.”
On average, strong shaking has affected the wider Hamilton–Hauraki region every 3,000 years.
“That doesn’t mean one is about to take place tomorrow – but it does mean the area has a real earthquake history.”
Implications for infrastructure and emergency preparedness
The Hamilton Basin stretches roughly 80 kilometres from Ngāruawāhia to Te Awamutu and about 50 kilometres west to east. It is a major corridor for roads, rail, power, water, and other essential services, and has significant population.
The findings will be added to the New Zealand Community Fault Model, helping long-term seismic hazard planning used for key infrastructure.
Earth Sciences New Zealand earthquake geologist Dr Pilar Villamor, also part of the research team, says events such as the 2010-11 Canterbury earthquakes highlight the risks posed by hidden faults.
“Even though a large earthquake is very unlikely to occur in most people’s lifetimes, Hamiltonians should still be prepared for strong shaking, and having an emergency plan and kit is essential .”
Collaboration, iwi partnership and funding
The four-year project was led by University of Waikato geoscientists Professor Lowe, Dr Max Kluger, Dr Vicki Moon and Dr Tehnuka Ilanko, along with graduate students and collaborators at Earth Sciences New Zealand, the University of Auckland, I-MED Hamilton Radiology, and Swansea University (UK).
The project was supported by iwi including Ngāti Wairere and Ngā Iwi Tōpū o Waipā, as well as local and regional councils and the Department of Conservation.
Funding was provided by the Marsden Fund, MBIE Endeavour Fund, Natural Hazards Commission, MBIE Strategic Science Investment Fund, QuakeCoRE, and Waikato Regional Council.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Emeritus Professor David Lowe, University of Waikato and study co-author, comments:
"This research reveals, for the first time, the earthquake history of the Hamilton lowlands area for the past 20,000 years. Previously, little was known about the region other than its low historical seismicity record of ~150 years. However, the 2010-2011 Canterbury earthquakes showed that major ground-shaking rupturing can occur and significantly impact surrounding communities even in areas of low historical seismicity. In the Hamilton area, two hidden faults running approximately north-south through Hamilton City were discovered in 2015 during construction of the Waikato Expressway. Their discovery was the catalyst for this research.
"A Waikato University-based multidisciplinary team comprising geoscientists and engineers developed an entirely new method to discover the earthquake history by revealing which faults had ruptured, when they ruptured, and the magnitudes of the rupturing (seismic) events.
"The method involved identifying, characterising, and dating liquefied volcanic-ash (tephra) layers preserved in multiple lakes, which are about 20,000 years old, scattered throughout the lowlands. The tephra layers, which have known ages from previous studies, were liquefied by violent seismic shaking and are termed ‘tephra seismites’.
"Multiple cores were taken from 18 widespread lakes and scanned using medical CT imaging to reveal the tephra seismites preserved within organic lake sediment and to accurately measure their sizes (Fig. 1). Other properties were measured in the laboratory. Analyses of the cores and scans in space and time showed where the strongest ground shaking occurred (forming the largest and most seismites), allowing liquefaction-severity maps to be generated. These maps showed which faults ruptured, and when.
"A procedure known as seismic modelling involving the development of peak ground acceleration (PGA) maps enabled the team to compare various seismic scenarios on all likely faults in the region, and for the offshore Hikurangi margin, and to compare these PGA maps with the liquefaction-severity maps.
"Five major paleoearthquakes have occurred since 15,700 years ago, three of magnitude (Mw) ≥7.0, on at least four faults. The average recurrence interval is ~3000 years. Notably, two earthquakes (SE2b, SE4) occurred within only the past 1700 years.
"Knowing the earthquake history is essential in planning for key infrastructure (such as hospitals, power facilities, and transport networks), especially in the central Waikato area of rapidly increasing population and development.
"The new paleoseismological method is applicable in some other regions in New Zealand, and globally where seismicity and volcanism occur (e.g., Iceland, Japan, northwestern USA/Canada, Italy, Chile)."
Multimedia
