The Wellington–Mōhaka Fault
The North Island’s longest active fault runs from Cook Strait to the Bay of Plenty. The southern section is the Wellington Fault; the northern section is called the Mōhaka Fault. The Wellington section presents a major hazard, as it goes through the heart of New Zealand’s capital city and is crossed by numerous bridges, roads and pipelines. About three-quarters of the people in the Wellington region live within 10 kilometres of the fault.
Wellington owes its distinctive landscape to this fault. Near the coast, the sea has flooded into the fault depression to create Wellington Harbour. During earthquakes along the fault, land along the north-western side of Wellington Harbour and the Hutt Valley moves upward, while in areas south-east of the fault land subsides.
Further inland, the Hutt River flows down the depression and has filled the Lower and Upper Hutt areas with hundreds of metres of sediment.
Movement along the 75-kilometre-long segment of the Wellington Fault from Cook Strait through Wellington and the Hutt Valley to Kaitoke is considered likely to cause a major earthquake in the future. At least two earthquakes have occurred on this part of the Wellington Fault in the last 1,000 years, with the most recent less than 310 years ago. During the last four earthquakes, sections of land on opposite sides of the fault moved past each other by about 5 metres. Such movement would produce earthquakes of the order of magnitude 7.5.
Large earthquakes on this section of the fault are estimated to occur about every 500 to 1,000 years.
Credit to Te Awa for the text and to the legend Julian Thomson for the YouTube video tour, Credit and thanks to the superhumans at GNS Science for the flyover.
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