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Unearthing quake information

The Hikurangi subduction zone where the Pacific tectonic plate dives under the Australian Plate. PHOTO/GNS SCIENCE

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Little is known about the Hikurangi subduction zone running off the coast of Wairarapa, which could be the source of a major earthquake and east coast tsunami.

But a panel of New Zealand’s leading scientists have shared their research with Wairarapa residents in the hope of bringing information to the surface.

More than 200 people came close to filling the Carterton Event Centre to hear from the researchers last week, many living on land which had been used in recent research.

Subduction zones can be found where tectonic plates meet and one plate moves under another and is forced into the molten rock below the earth’s crust.

Since 2016, a large team of national and international scientists have been studying the plate boundary to help forecast the likelihood of damaging earthquakes or tsunamis.

Many residents were surprised to find the research had included testing along parts of Wairarapa, including stretches of coastline near Glenburn.

Dr Kate Clark, an earthquake geologist from New Zealand Geoscience Society, said the research was important for better understanding how these processes work and what might happen in the event of an earthquake along the Hikurangi subduction zone.

“We don’t have historic examples of subduction zone earthquakes in New Zealand. But we do have a geological record to have a look at.”

The Hikurangi subduction zone rests off the east coast of the North Island where the Pacific tectonic plate dips below the Australian tectonic plate.

The plate boundaries along Wairarapa and Wellington are in a “stuck” zone where no movement has been detected.

Were the boundary to rupture, the result would be an earthquake event up to 8.5 on the Richter magnitude scale.

But that shouldn’t be cause for immediate concern as it may be hundreds of years before such events occur.

There have been five major seismic events, potentially subduction zone earthquakes, in Wairarapa in the past 7000 years – three of which occurred in the past 2000 years.

Dr Laura Wallace, a geophysicist from GNS, presented her research showing how the fault was moving, which included studies of slow slip events.

“We need to better understand this relationship between slow slip events and damaging earthquakes.”

She said slow slips were believed to happen as far south as Castlepoint but not much further than that.

The event was a good opportunity for residents to think about their own disaster preparedness measures, with many discussing the subject as they left.

Be prepared for the next big one

Long or strong get gone:

If you are in a tsunami evacuation zone and feel a strong earthquake that makes it hard to stand up, or a weak rolling earthquake that lasts a minute or more, move away from the coast immediately.

Emergency supplies and getaway bags:

In an emergency you could be stuck at home for three days or more. You probably have what you will need already, and you don’t have to have everything all in one place, but you might have to find things in a hurry and/or in the dark. It is a good idea to have a pre-packed getaway bag if you live or work in a flood or tsunami zone.

Making a plan:

Talk with your family and friends. Work out what you’ll do in emergency situations and how you’ll communicate. When developing your plan, think about not being able to get home, having to evacuate, being stuck at home and having no water, no power and no communication.

Connecting in an emergency:

In an emergency people generally need two things – contact with others and information. In an emergency people will check on each other and share resources. Knowing a variety of people in your local and wider community will make you able to manage better in an emergency.

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