There are 3 places on board where we can steer the ship. First and foremost is the bridge. This is where either the Captain or one of the mates can be found and usually who has control. The second place we can steer from is the Main Lab. This is where the science party can be found on shift, doing data quality control, taking logs and monitoring all the equipment. We often steer from here while collecting data to keep our streamers recording at full coverage. There are A LOT of screens in here! The final place we can steer to boat from is the engine room. This area is usually off-limits for the science party, but today we were lucky enough to be taken on an engine room tour. The chief engineer Matt took us into ‘the belly of the beast’, as he called it, where all the machinery that keeps the boat up and running can be found. After a brief chat in the control room, we put on our ear protectors and went exploring. The engines themselves are pretty huge, and are used to power 2 rotating shafts which drive the boat. Matt took the cover off so we could see all the pistons moving as the engine chugged away. The shafts are attached to propeller blades which can be moved outwards, perpendicular to the rotation, to control the ship’s speed. The speed of the ship depends on the angle of the propellers. The engine produces a huge amount of heat, but this is not wasted and is used to create fresh water for us while on board. Fresh water can be made in 2 ways on here, by an evaporator which harnesses heat produced by the engine, and we top this up by reverse osmosis of sea water. There are 2 other, smaller engines that are used to power the compressor. This is a five-stage process which compresses air to 2000psi for use in our data acquisition. This is all done below deck. Besides the scientific side, all the practicalities for life on board stem from the engine room. There are machines for air conditioning, hot water, freezers and waste down here. There is also a separate room of hydraulic equipment for closing watertight doors and using winches and cranes. Besides the chief, there are 3 engineers, Mike, Joseph and Alexander, as well as 3 oilers, Guillermo, Gregory and Jack and one electrician, Michael. They spend most of their time in the very hot and noisy engine room making sure we are plain sailing as we collect all out data. It was really amazing to see the scale of operations going on just below us, and how much it takes to keep us going, all the way from driving our data acquisition to making sure we have a warm shower. Besides this fun afternoon, data acquisition is going really well with 3 lines to go! We have had some great weather and made the most of it with dinners on deck and some beautiful scenery of New Zealand when data collection brings us close enough to land.
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We commonly get asked about marine life when conducting these sort of scientific studies. The environment is very important to us, and the ship takes this job very seriously. Onboard we have a team of PSOs. This stands for Protected Species Observers who constantly look out for any marine mammals, turtles, and birds. The PSOs can be found either in the lab or on the observation tower. The observation tower is the tallest point on the ship and is equipped with 2 giant pairs of binoculars. There are 2 PSOs on shift from 30 minutes before sunrise to 30 minutes after sunset, constantly looking out for any species. There is a 500m exclusion zone from all acoustic equipment, within which, if a marine mammal or pinoped is spotted, action is taken. If a mammal comes into the exclusion zone, the pressure of the acoustic waves we are producing is lowered to about 1/10th it’s normal pressure and the exclusion zone is decreased to 100m. If the mammal then enters the new exclusion zone, everything gets shut down. The mammal is monitored, and starting up doesn’t resume again until it has left the exclusion zone. A detailed report is taken of all species seen as well as any changes in behaviour within the exclusion zone and after shutdown. When we turn on the instruments we also do it by ‘ramping up’ which means slowly increasing the pressure, so any mammals can leave the area as the pressure gradually reaches maximum. PSOs in the lab are using Passive Acoustic Monitoring systems, or PAM, 24 hours a day. This is sort of like a microphone which is towed behind the boat listening out for any mammals. These are usually clicks and whistles which can be used to track the mammals, calculate their bearing, and determine the range. PAM works really well but it’s difficult to identify a specific dolphin species from the clicks and whistles as they sound similar. Other mammals, such as Sperm whales, for example, have a much more distinctive sound. There are 3 exceptions to shutdowns. The only one we will come across in this region is the common dolphin. A lot of research has been done about this species and it has been found that these curious guys have been known to swim right up to the ship and bow ride for a while, seemingly quite curious about the acoustic instruments. We have been lucky enough to see a few playfully jumping through the waves along the bow! We have also seen many birds, including an albatross or two. There are 5 PSOs onboard: Amanda, Sara, Brooke, Becky and Mark. While these guys work really hard, they are always happy to let us science crew come up to the observation tower for a look, and let us know if there are any sighting so we can go out and see for ourselves. They are all super knowledgeable about the marine life in the area and have loads of really interesting facts. The whole science party has had a turn wearing the PAM headphones listening to the clicks and whistles of nearby dolphins and it’s really amazing! It’s been a great cruise so far and fortunately no mammals, besides the common dolphin, have come near the exclusion zone, so data collection is going really well!
With all the land seismometers and OBS instruments now in place and waiting patiently for the data to roll in, it’s time for the marine part of our experiment to begin! The vessel we are using is the R/V Marcus G Langseth, a research vessel from Lamont-Doherty Earth Observatory in New York. The science party joined the main ship’s crew in Tauranga and the salty sea life began! The science party on board is a bit different to the land deployment crew. On the Langseth there are a mix PhD students, early career scientists, and more senior staff from the UK, USA, New Zealand and Japan. First things first, we had a safety drill. We all had to go to our muster stations when the alarm rang and grab a life vest and immersion suit. Everyone then gathered on the bridge and the captain briefed us on what to do in an emergency and we got a demonstration of how to put the immersion suits on. Next was time for us to try and put them on ourselves. All the crew can go from human to lobster in under 60 seconds which, trust me, is no easy feat!! The R/V Marcus G Langseth is a brilliant research vessel, equipped with all we need to start acquiring our data. The crew are super friendly and enjoy getting the science party up on the decks to help deploy all the kit. The ship will be towing 4 streamers, each 6km long, as well as the acoustic source generators. That’s a lot of kit to be towing! We started early one morning putting out the streamers one by one to test they were in ship-shape (haha) condition and that all the birds were working and in the right place. Birds are plastic tools that get their names from small wings that protrude either side. These are no ordinary pigeons though! The birds can communicate with each other and the main lab, and the wings can be moved to keep the streamers as straight as possible, stop them from tangling up with each other, and make sure they stay at the right depths. We want our streamers to be 8m below the sea surface. Once we are sure everything is in working order, everything gets pulled back in ready for the real deal. The whole testing process takes about 3 days. Next we headed over to the survey area. This is 17km offshore from the area around Gisborne (where we were deploying the land instruments) at its closest, and 77km at it’s furthest. Once there, we put all 4 streamers out, using 2 paravanes. Paravanes are large buoys which help keep the streamers spread out and away from each other. Getting the streamers tangled up would be terrible! The acoustic source generators are next. These will be operating in flip-flop. No not the shoe, this means one releases an acoustic wave, and then the other, then back to the first, then… you get the idea. The acoustic waves generated here will travel down through the rocks in the subsurface, and get recorded by the streamers, the OBS instruments lying on the seafloor, and of course, our land seismometers. Pretty clever right?! Once we’ve finished, we will be able to pick up all our instruments, download all the data, and use it to make a beautiful 3D map of the subsurface of the Hikurangi margin. But that’s a long way off. We’ve only just started recording data and will be out here for 5 weeks in total. But so far so good!! Everything seems to be going to plan and the data we can see from the streamers is looking pretty nice. The science party! Shuoshuo (UT), Ryuta (JAMSTEC), Harold (University of Wisconsin-Madison), Melissa (Imperial College), Dan (GNS), Stephen (University of Wisconsin-Madison), Harry (University of Cardiff), Joel (UCSC), Nathan (UT) and Hannah (University of Hawai’i) [Missing: Time (University of Birmingham)] |
AuthorThe NZ3D FWI team consists of over 20 scientists from the UK and New Zealand who will be involved in installing over 200 seismometers! Archives
February 2018
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