Scientists Investigate Tsunami Potential In Kaikoura Canyon
Scientists Investigate Tsunami Potential In Kaikoura Canyon
Scientists will be working off the east coast of the South Island next week investigating the potential for a landslide tsunami in the head of the Kaikoura Canyon.
The Kaikoura Canyon is up to
2000 metres deep in places and comes within 500 metres of
the coast south of Kaikoura, closer than any other New
Zealand submarine canyon.
It is in an active seismic
region, with faults such as the nearby Hope Fault capable of
producing large earthquakes.
Last year NIWA scientists
successfully mapped the shallow reaches of the canyon
between Oaro and Goose Bay. The Kaikoura Canyon
investigation is part of an ongoing programme with
Environment Canterbury to understand the hazard posed to the
Canterbury coastline from tsunamis.
That project is
now being followed up by fieldwork from NIWA’s research
vessel Ikatere to assess the strength of sediment
layers at the canyon head.
NIWA marine geologist and
project leader Dr Joshu Mountjoy says the seafloor drops off
steeply into the Kaikoura Canyon.
“Our work last
year showed us that several different types of landslides
can occur here, and we need to understand what will happen
to the rock and sediment during an earthquake,” Dr
Mountjoy said.
Determining the strength of the
sediment layers will enable the scientists to figure out
what changes are needed to make it slide. If the layer is
weak it will slide easily, but denser layers are likely to
be stronger and more stable.
Understanding more about
the hazard potential in the canyon will enable vulnerable
coastal communities to build resilience and be better
prepared for natural hazards.
“It is very important
to understand how big these tsunamis can be, and where and
when they might occur,” Dr Mountjoy said. “This
fieldwork will fill in a significant piece of the puzzle and
will enable us to undertake sophisticated numerical
modelling to better understand the landslide tsunami
potential.”
Dr Mountjoy will be joined on the
research vessel by doctorate students from the University of
Canterbury and the University of Bremen in Germany. The team
will use a new coring system to retrieve sediment from a
range of water depths for testing in the engineering
laboratory at the University of Canterbury.
A
state-of-the-art free-fall Dynamic Cone Penetration (CPT)
system from the Marine Geotechnics department at the
University of Bremen will be used to measure the strength of
the sediment. The CPT is also used to see if there is any
pressure within the sediment that might weaken the slopes
and make it easier for landslides to
occur.
“Geotechnical measurements will allow us to
use numerical modelling to determine the response of the
shallow seabed to future earthquakes,” Dr Mountjoy
said.
The Kaikoura District Council, Civil Defence and
Environment Canterbury are holding a Community
Preparedness/Tsunami Information roadshow on March 19 and 20
in Kaikoura, Clarence and Goose Bay.