New research has pinpointed an active fault close to New Zealand’s largest city, indicating a potentially higher earthquake threat for Auckland. The Mangatangi Fault, situated around 50 km south of the city along the Hunua Ranges, has the capacity to trigger an earthquake reaching up to magnitude 6.8, as per a University of Auckland press release. The fault has shown signs of movement within the last 10,000 years, categorizing it as active in geological terms.
The study, published in the New Zealand Journal of Geology and Geophysics, underscores the limited understanding of the fault’s seismic history. Geologist James Muirhead, a co-author of the study from the University of Auckland, warned of significant repercussions if the entire fault were to rupture, particularly for residents in South Auckland and potentially extending into central Auckland. This marks the first instance of radiocarbon dating of a faultline in the Auckland region, shedding light on the inadequate awareness of its seismic risks.
According to Muirhead, Auckland encounters earthquakes annually, although most are too minor or distant to be felt. The recent findings coincide with Auckland’s urban expansion towards the southwest, bringing more individuals and infrastructure closer to the fault line. Researchers advocate for a reassessment of the city’s seismic hazard level, which could lead to stricter building regulations. Auckland had been exempted from earthquake-prone building regulations last year due to its perceived low risk.
Lead researcher Hannah Martin from the University of Auckland emphasized the fault’s active nature and its potential to trigger a significant earthquake in an area unaccustomed to such events. The region experiences numerous earthquakes daily, with over 20,000 recorded annually, although the majority go unnoticed. However, between 150 and 200 earthquakes each year are substantial enough to be felt, with historical data revealing the toll of earthquakes in New Zealand over the years.
