Preparing for the big one

Fault Graph

Scientists and emergency services have started to plan how the East Coast will respond when a “credible” threat of a 8.9 magnitude “mega-thrust” earthquake hits the region.

Led by umbrella group East Coast Life at the Boundary (LAB), the Hikurangi Response Plan will outline how to respond to a Hikurangi subduction zone earthquake and tsunami, and how to enhance communities’ preparedness for an event that scientists say is a case of when, not if.

Project Lead, Natasha Goldring, said building the collaborative response plan was vital in lifting readiness for, and resilience to, a future earthquake and tsunami on the Hikurangi fault.

Using a credible magnitude 8.9 earthquake and tsunami scenario, five Civil Defence Emergency Management (CDEM) groups from across the North Island East Coast are working together to develop an emergency response plan that has communities at its heart.

“The scenario we are using to support the development of this response plan is a very realistic example of what we could face in our lifetime, or that of our children and grandchildren.”

Goldring said although the $240,000 project was being driven by CDEM groups, people still needed to make sure they understood the risks they faced and take the necessary steps to prepare themselves.

Information on how to prepare for an earthquake or tsunami can be found at www.happens.nz.

The launch of the project comes in response to research over the last several years that suggests the likelihood of a rupture may be higher than initially understood.

GNS geophysicist Dr Laura Wallace said new insights had been gained following the Kaikoura earthquakes, adding there was also evidence for pressure building on the fault,which lies just 50km off the Gisborne coast.

“A subduction zone is where one tectonic plate subducts (dives) underneath another. The boundary between these two plates forms a large fault. This one in particular runs offshore from the east of Gisborne down to the top of the South Island and poses a significant earthquake and tsunami risk to the entire east coast of New Zealand.”

Dr Wallace said subduction zone faults had been responsible for most of the world’s deadliest earthquakes and tsunamis to date, with Japan 2011 being the most recent example.

“We know the Hikurangi subduction zone can produce large earthquakes and tsunamis, and these events have happened in the past.

“While we’re carrying out more research to build a clearer picture of the hazard posed by the Hikurangi fault, we know a rupture at some point in the future is certain.”

Speaking to The Gisborne Herald, Dr Wallace said new paleo-seismic research had shown large scale earthquakes had happened between every 300 to 800 years — twice as frequently as people had previously believed.

“Evidence has also been building up over the last 10 or 15 years as we’ve been able to better resolve what exactly is happening on the subduction zone. Right now, GPS measurements we have been doing show parts of the fault are locked up and building up stress that will eventually be relieved in the future.”

Dr Wallace said the combination of evidence “really confirms that this is a hazard that we need to worry about”.

A series of planning workshops scheduled for next month will engage the many stakeholders involved in the process, including CDEM, local and central government, infrastructure providers, emergency services, hospital and health providers, non-government organisations, experts from various universities and key business sectors.

See also today's editorial.