Hikurangi subduction zone expedition #375 – blog 1

In March 2018, JOIDES Resolution, a large scientific research vessel, headed out to sea to research the Hikurangi subduction zone on expedition #375. This article is the first blog by Aliki Weststrate, IODP (International Ocean Discovery Program) Outreach Educator. This is her account of a voyage full of excitement, challenges and science!

Our adventure began in Timaru on 9 March 2018, and it will end in Auckland on 5 May.

Thirty-four scientists from 10 different countries around the world dragged their heavy suitcases up the gangplank for the first of 60 days on board the research vessel JOIDES Resolution.

Who else is on board?

We also have 25 very experienced and talented technical crew on board who train incoming scientists on all the high-tech equipment in the labs and generally keep the science going. There’s a huge range of jobs on board, and everyone has a specific role to fill to ensure the boat runs smoothly and we fulfil our science aims.

The ship itself has 50 staff who fix the engines, thrusters, drilling equipment to drill into the Earth, cranes, drill rig and electronics. And we can’t forget the catering and cleaning staff – there are 18 on board, and they keep us comfortable and well fed. In fact, it will be hard not to overeat.

Over the course of the 2-day transit from Timaru to east of Gisborne, the whole crew transitions to the night shift or the day shift. I drew the short straw and have to work the midnight to noon shift. The boat is fully operational 24/7, so it makes the most of the time it has at a site to get the most data. We also do lifeboat training and lab training during the transit.

This ship is 143 m long (that’s one and a half rugby fields!) with a central derrick (tower) which holds the drill pipe. This drill pipe is extended with 40 m pipes – one attached at a time like joining straws together. The drill pipe goes all the way to the seafloor and then even lower by drilling through the mud and sand. Inside the steel drill casing is a drill string, which brings up long tubes of core 10 m at a time, much like an apple corer going into an apple.

Why do we want core samples?

Core samples from below the seabed are one of the only ways we can see what has happened to the Earth over time. For our expedition, we want to drill into the frontal thrust fault that sits above the Hikurangi plate boundary. The boundary is called a subduction zone. Subduction zones develop a type of fault that are responsible for the largest and most powerful earthquakes and tsunamis in the world, such as Sumatra 2004, Chile 2010 and Japan 2011. By bringing up core from this region, we can learn a lot more about the subduction zone and its properties (such as density, porosity, lithology, thermal conductivity, frictional properties, age and fluid pressure in the rock). This tells scientists how it was formed and what condition it is in right now. The frontal thrust area is also where geologists think slow slip events are occurring, so taking samples of this for study will shed some light on why they are creeping slowly in 'silent earthquakes' rather than moving fast in earthquakes that we feel.

It's a fascinating ship. The effort going into the engineering and science is totally incredible. Humans are very determined!

Aliki Weststrate

What’s next?

Next week, we will attempt to lower a CORK observatory under the seafloor into a new 450 m narrow chamber, near our first borehole. CORK stands for circulation obviation retrofit kit, playing on the obvious analogy of a cork sealing a bottle.

This is the first time one has been installed in New Zealand, and it will stay there for 5–10 years. The sensors inside it will measure the temperature, fluid flow and pressure, and chemistry of the fault itself. Because it is there for such a long time, it will record earthquakes and slow slip events as they happen – this will give us new insights into its behaviour over time.

The overall aim of this voyage is to understand the Hikurangi subduction zone much better, so we can improve New Zealand’s hazard modelling for earthquakes and tsunamis. A deeper understanding will improve hazard preparedness for New Zealand communities.