Auckland’s earthquake and volcanic history is being dramatically re-evaluated after University of Auckland researchers uncovered evidence of far more seismic activity beneath the city than previously understood.
The groundbreaking research is reshaping scientific understanding of Tāmaki Makaurau’s underground geology and raising fresh questions about how prepared New Zealand’s largest city is for future volcanic or seismic activity.
Researchers working on the Auckland Volcanic Field have identified dozens of previously unknown fault structures beneath the city while detecting significantly more small earthquakes than earlier monitoring systems recorded.
Scientists say the findings effectively rewrite Auckland’s geological history and reveal a much more dynamic underground environment than many people realised.
Auckland sits directly atop the Auckland Volcanic Field, a massive volcanic system made up of more than 53 volcanoes formed over the past 200,000 years. The field stretches beneath homes, businesses, roads and critical infrastructure across the region.
Unlike dormant volcanoes with central cones, Auckland’s volcanic field is considered monogenetic, meaning future eruptions are expected to occur at entirely new locations rather than existing volcanoes reawakening.
The new research combines machine learning, borehole analysis and seismic monitoring technology to map underground fault systems hidden beneath the urban landscape.
Among the most significant discoveries are probable fault lines stretching between the Waitematā and Manukau harbours, including structures running through suburbs such as Avondale, Glendowie and Blockhouse Bay.
Additional possible fault systems have also been identified around Northcote, Birkenhead and Wiri.
Researchers say the findings do not mean a catastrophic earthquake is imminent, but they do improve understanding of Auckland’s underlying volcanic and seismic risks.
The Auckland Volcanic Field is already regarded as one of the country’s most complex natural hazard environments because it combines volcanic, seismic and urban risks within a densely populated region of more than 1.7 million people.
Scientists say small earthquakes are expected to be one of the earliest warning signs of volcanic unrest, making accurate seismic monitoring essential for emergency preparedness.
The discoveries are part of wider work being carried out through DEVORA — the multi-agency programme established to better understand volcanic risk in Auckland.
Researchers involved in the programme say improved geological mapping will help planners, engineers and emergency management agencies make better decisions around future development, infrastructure and disaster readiness.
The findings also reinforce growing concerns around how urban expansion has occurred across Auckland’s volcanic landscape.
Large sections of the volcanic field have already been heavily modified through housing development, quarrying and infrastructure construction, with some volcanic landforms destroyed entirely during urban growth.
Geologists warn this makes understanding buried fault systems and hidden volcanic structures even more important as Auckland continues expanding.
For Māori, the discoveries carry additional cultural significance.
Many volcanic cones and geological sites across Tāmaki Makaurau hold deep whakapapa connections and are recognised as wāhi tapu connected to ancestral histories and mana whenua identity.
Volcanic maunga such as Maungawhau, Maungakiekie and Ōwairaka remain central to the cultural landscape of Auckland and are protected through co-governance arrangements involving mana whenua.
Researchers say understanding the geological history of the region is also part of protecting these culturally significant environments for future generations.
The research comes amid increasing international attention on urban volcanic systems and how cities prepare for low-frequency but high-impact natural hazard events.
Although the probability of a major eruption or destructive earthquake remains low in the short term, scientists stress Auckland remains an active volcanic field and future activity cannot be ruled out.
Past eruptions within the field have ranged from small localised lava flows to explosive crater-forming events involving ash, gas and significant landscape change.
Some modelling suggests a future eruption occurring within densely populated urban Auckland could cause major disruption to transport, housing, utilities and economic activity.
Emergency management agencies already maintain volcanic contingency plans for Auckland, including seismic monitoring networks designed to provide early warning signs of volcanic unrest.
Researchers say the latest discoveries are ultimately about preparedness rather than panic.
By improving understanding of Auckland’s hidden geology now, scientists hope the city will be better equipped to respond to whatever natural hazards emerge in the future.
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