Researchers from GNS Science have been working at the Pakarae River mouth north of Gisborne looking for evidence of past tsunami and earthquake events.
Dr Nicola Litchfield from GNS Science says 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.
“Our previous research shows that three or four large tsunami have struck the East Cast in the past 1200 years and three large earthquakes have occurred in the past 1800 years,” says Dr Litchfield.
She says coastal sites that provide good evidence of tsunami are rare but sites in Gisborne are known to contain a good archive of events such as these.
The researchers’ work involves digging a 165m-long and 1.5 m deep trench on coastal land that has been uplifted in an earthquake to look for evidence of past quakes and tsunami in the trench walls.
“This will help us to better understand the behaviour of the Hikurangi plate boundary, New Zealand’s largest earthquake and tsunami hazard”, says Dr Litchfield.
The trench was dug in March and during the next few months scientists will use a variety of analysis techniques including radiocarbon dating of uplifted shells to try and pinpoint the timing of past earthquakes.
Further studies of sediments and rocks will be carried out at different sites in Tairāwhiti, Hawke’s Bay, Wairarapa, Marlborough and Kaikōura to help piece together the earthquake and tsunami history of the East Coast.
Dr Litchfield says studies such as this provide valuable knowledge to help understand and better plan for future events.
The research is part of a five-year Ministry of Business, Innovation and Employment (MBIE) research programme called ‘Hikurangi Subduction Earthquakes and Slip Behaviour’ and GNS Science would like to thank the Whangara Farms Trust for supporting the trenching study.
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