Underwater core samples will help assess risk

A graph measuring tool.

ANALYSIS of core samples taken from the seabed off the east coast will help to assess the risks of large underwater earthquakes. The international research is a five-year project. A team of scientists conducted a survey in November aboard Niwa’s research vessel, Tangaroa, looking for evidence of past earthquakes off the North Island’s east coast.

The scientists were looking for geological evidence of strong ground shaking to try to reconstruct where and when earthquakes have occurred along the Hikurangi plate boundary, New Zealand’s largest earthquake and tsunami hazard.

“We were looking for marine ‘turbidites’, layers of mud, sand and gravel sediment, which settle as a result of seafloor landslides triggered by earthquakes,” says Niwa marine geologist and voyage leader Dr Philip Barnes.

The scientists surveyed more than 50 sites between Cook Strait and Poverty Bay, despite occasional rough seas, and collected sediment cores up to six metres long. When the cores were brought on board, they were measured and cut into sections to be photographed, X-rayed, logged and packaged for further analysis.

“This analysis will be tackled as part of a five-year project. When completed, it will help assess the hazard, risk and, ultimately, potential losses due to large earthquakes on the Hikurangi plate boundary,” says Barnes.

The work involves scientists from various national research institutions (including Niwa, GNS Science, University of Auckland, University of Otago, University of Canterbury, and Victoria University of Wellington), as well as international researchers from the US, Turkey, and France.

The research is part of a five-year NZ Ministry of Business, Innovation and Employment (MBIE) research programme called Hikurangi Subduction Earthquakes and Slip Behaviour and a multi-year Niwa-MBIE Core Coasts and Oceans Programme Marine Physical Processes and Resources.