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Digging for earthquake evidence

2 months ago by Kate Boersen


Scientists searching for evidence of past earthquakes have dug a 90 metre long trench in Aramoana, southern Hawke’s Bay.

They selected the site at Aramoana as it has been uplifted in a series of large earthquakes over the last 8000 years to create three marine terraces. Marine terraces usually provide good evidence to date past earthquakes.

“We are specifically looking for shells that we can later radiocarbon date in the lab to try and pinpoint the timing of past earthquakes and tsunami” says Project Leader Dr Nicola Litchfield.

“If we identify evidence for an earthquake at only one location, then it is likely this event occurred on nearshore faults, which will have uplifted and shaken a relatively small area.

“But if we identify evidence at multiple site, that points to a Hikurangi subduction zone earthquake.”

Scientists have known for a long time that the East Coast has experienced a number of large earthquakes in the past but are still trying to figure out how big and how often these events occurred.

GNS Science experts are trenching in many coastal locations, while NIWA, Victoria University of Wellington and University of Auckland are also looking at sites off the coast at Aramoana for evidence of earthquakes.

These two studies will combine to build a picture of past earthquakes.

The research is part of a five-year Ministry of Business, Innovation and Employment (MBIE) research programme called ‘Hikurangi Subduction Earthquakes and Slip Behaviour’.

This research will provide valuable knowledge to help understand our earthquake and tsunami risk along the East Coast of the North Island of New Zealand.