Scientists comb Wairoa lagoon for past tsunamis

Cooperation between US and Kiwi scientists not quite draining the swamp but is getting to bottom of Ohuia lagoon near Wairoa.

Cooperation between US and Kiwi scientists not quite draining the swamp but is getting to bottom of Ohuia lagoon near Wairoa.

CORE TEST: Dr JessicaPilarczyk from the University of Southern Mississippi collects core samples from a lagoon in Wairoato test for evidence of
past tsunami events. Picture supplied

A COMBINED team of United States and New Zealand scientists is trying to find out if Ohuia lagoon, near Wairoa, was once swamped by a tsunami.

As part of a United States research programme scientists from the University of Southern Mississippi and GNS Science have been surveying various field sites along the East Coast looking for evidence of past tsunamis and earthquakes, included sites in Wairoa.

GNS Science paleoecologist Ursula Cochrane said the lagoons east of Wairoa are known to contain a good archive of old earthquakes and tsunamis but the current focus is on more recent events.

“Finding evidence of large tsunamis and earthquakes that have hit the area prehistorically can help us learn more about what might happen in the future.”

Dr Cochrane said the team initially carried out a visual assessment of sediment layers and, if those were considered worthwhile, a sediment core was taken using a long steel, tubular sediment corer and a sediment core taken at Ohuia Lagoon near Wairoa was already of interest to the scientists.

The lagoon is located at the end of Ohuia Road and to get a core sample, the corer is pushed as far into the ground as possible; when it cannot go any further, it is then pulled to the surface and analysed.

Assistant professor Jessica Pilarczyk from the University of Southern Mississippi pointed out that before scientists could say for sure whether or not the cores provided evidence of past tsunami events, the recover sediment needed to be analysed.

“We’ll take these cores back to the lab and look at them under the microscope, and do things like high resolution grain size analysis, palaeontological analysis and geochemical analysis.

“While this analysis takes quite a bit of time, it will help provide evidence of past earthquakes and tsunamis. This information can then be used to understand and better plan for future events.”

The work is part of a four year US National Science Foundation (NSF) funded research programme called the ‘SHIRE: Seismogenesis at Hikurangi Integrated Research Experiment’, which ties in with a five-year Ministry of Business, Innovation and Employment (MBIE) research programme called the ‘Hikurangi Subduction Earthquakes and Slip Behaviour’.

Further field work will be carried out early next year and details of the work and the scientists’ progress will be available through East Coast LAB (Life at the Boundary) website.

East Coast LAB is a collaborative project that brings together scientists, emergency managers, experts and stakeholders across the East Coast to make it easy and exciting to learn more about the natural hazards that can life on the East Coast.

A COMBINED team of United States and New Zealand scientists is trying to find out if Ohuia lagoon, near Wairoa, was once swamped by a tsunami.

As part of a United States research programme scientists from the University of Southern Mississippi and GNS Science have been surveying various field sites along the East Coast looking for evidence of past tsunamis and earthquakes, included sites in Wairoa.

GNS Science paleoecologist Ursula Cochrane said the lagoons east of Wairoa are known to contain a good archive of old earthquakes and tsunamis but the current focus is on more recent events.

“Finding evidence of large tsunamis and earthquakes that have hit the area prehistorically can help us learn more about what might happen in the future.”

Dr Cochrane said the team initially carried out a visual assessment of sediment layers and, if those were considered worthwhile, a sediment core was taken using a long steel, tubular sediment corer and a sediment core taken at Ohuia Lagoon near Wairoa was already of interest to the scientists.

The lagoon is located at the end of Ohuia Road and to get a core sample, the corer is pushed as far into the ground as possible; when it cannot go any further, it is then pulled to the surface and analysed.

Assistant professor Jessica Pilarczyk from the University of Southern Mississippi pointed out that before scientists could say for sure whether or not the cores provided evidence of past tsunami events, the recover sediment needed to be analysed.

“We’ll take these cores back to the lab and look at them under the microscope, and do things like high resolution grain size analysis, palaeontological analysis and geochemical analysis.

“While this analysis takes quite a bit of time, it will help provide evidence of past earthquakes and tsunamis. This information can then be used to understand and better plan for future events.”

The work is part of a four year US National Science Foundation (NSF) funded research programme called the ‘SHIRE: Seismogenesis at Hikurangi Integrated Research Experiment’, which ties in with a five-year Ministry of Business, Innovation and Employment (MBIE) research programme called the ‘Hikurangi Subduction Earthquakes and Slip Behaviour’.

Further field work will be carried out early next year and details of the work and the scientists’ progress will be available through East Coast LAB (Life at the Boundary) website.

East Coast LAB is a collaborative project that brings together scientists, emergency managers, experts and stakeholders across the East Coast to make it easy and exciting to learn more about the natural hazards that can life on the East Coast.

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