Back on land

After nearly one month at sea, we are happy to be back on land, proud that all our mission targets have been achieved. We are grateful to the mystic god Neptune, who kept the sea calm during our time at sea – that made our journey pleasant and work easier.We are looking forward to reunite with our families, however, for most of us returning back home is also another long journey, many taking long-haul flights. Until the next post, good bye for now.

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The PILAB deployment crew, happy to be back in Porto Grande, Cape Verde.

 

Clear deck, back to the port

Clear deck. All stations are now deep beneath the ocean.
Clear deck. All stations are now deep beneath the ocean.

Life on board has suddenly changed overnight. The labs are now cleared out; all gear brought in for the mission is locked in flight cases, ready to take the next journey after we arrive back to Porto Grande in Cape Verde. Some of us took the opportunity to explore the ship a bit more, in particular by paying a visit to the engine/power room – the heart of the ship. When looking at the photos, do not be mistaken to think that this is a tranquil environment. The engine rooms are loud, so loud that we could barely communicate. The sound of the powerful machine is a reminder how much force is needed to run the ship.

 

Voilà, all in the sea

We are proud to announce that all the 78 stations are at the ocean bottom! That is, 39 ocean-bottom seismic (OBS) and magnetotelluric (OBMT) stations have been deployed at 39 sites, 2 at each site. The last stations were released into the sea this morning at 08:45 UTC time. All the stations were deployed within an intensive 15 days time. Although this mission target has been achieved, it is still not yet over. Our return transit will take no less than 6 days to head back to Porto Grande in Cape Verde. Now it is time for all the scientific crew to rest and adjust to normal sleeping hours.

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The last OBS station to be deployed into the ocean was released by Principal Investigator Nicholas Harmon.

Links

We have set up a links page in the menu of this blog. This page will feature links to websites that report on PILAB progress, such as the ones below. Check them out, especially Daniel’s blog for some nice photographs from the deployment cruise.

 

The ‘seismogram’ of a sailing ship

We thought of doing some basic ‘seismic’ analysis of the R/V Marcus G. Langseth.

In the last few days we have been surveying the ocean seafloor. This process requires that the ship sail in the form of a grid in order for the echo sounder to map the bathymetry of the entire area. In between matters and watching the survey proceed, we thought of doing some basic ‘seismic’ analysis of the R/V Marcus G. Langseth. We recorded the ‘seismic’ trace using a laptop’s accelerometer. The data is in three components (dimensions): west-east (X), north-south (Y), and up-down (vertical, Z). As expected the sway of the ship dominated the recording. From frequency analysis we find that the strongest frequency in the traces is about 0.1 Hz, which corresponds to a period of 10 seconds… No surprises here that this probably is the period of the sea waves.

A three-component seismogram recorded on board the R/V Marcus G Langseth whilst sailing through the Atlantic Ocean. A long period wave dominates the signal in each of the components, west-east (X), north-south (Y) and vertical (Z).
A three-component seismogram recorded on board the R/V Marcus G Langseth whilst sailing through the Atlantic Ocean. A long period wave dominates the signal in each of the components, west-east (X), north-south (Y) and vertical (Z).
Spectral analysis: Frequency spectrum with time for the west-east (X) component seismogram. Low frequencies (
Spectral analysis: Frequency spectrum with time for the west-east (X) component seismogram. Low frequencies (<0.5Hz) have the largest amplitude on the power scale (db).
Spectral analysis: Frequency spectrum for the entire seismogram. The largest amplitude is at 0.1 Hz (10 seconds period).
Spectral analysis: Frequency spectrum for the entire seismogram. The largest amplitude is at 0.1 Hz (10 seconds period).

Oh no!

We lost the Internet connection. Perhaps we should have been grateful that we had Internet in the first place, even if it is slow connection! We were all prepared for the possibility that we will be without Internet throughout the entire journey, however, we had got used to the (luxuriously) Internet connection on board, at least we had some form of communication to the outside world. You only know what you had after you have just lost it – and makes you wonder how the Internet has become part of our daily life. Alas, the connection is now back, and here we are updating this blog 🙂

Nicer geophysics means more data

Following the 36th site deployment (out of 39) we have proceeded to make an ocean bottom survey of the Chain Fracture Zone, a major tectonic feature just south of the equator that cuts through the mid-Atlantic ridge. The survey is conducted using an acoustic multi-beam echo sounder. Acoustic signals are transmitted from beneath the hull and reflected back from the ocean bottom.

Seeing the ocean bottom in never-seen-before high resolution is an exciting experience.

Illustration of echo sounding using a multi-beam echo sounder. Figure source: wikimedia.org
Illustration of echo sounding using a multi-beam echo sounder. Figure source: wikimedia.org

The data is then processed in near real time, producing stunning bathymetric maps. Seeing the ocean bottom in never-seen-before high resolution is indeed an exciting experience. This, however, demands larger data storage and higher computing processing power.

The Chain Fracture Zone mapped using multi-beam echo sounder.
The Chain Fracture Zone mapped using multi-beam echo sounder.

For example the bathymetric images generated from a continuous operation require about 3.3 Gigabyte of data a day. More data is compiled by the other instruments (gravimeter, magnetometer, gyroscope, thermosalinograph, weather station, GPS, CHIRP) generating a couple of hundred megabytes a day. This does not take into account the data that is being collected from the 39-ocean bottom magnetotelluric and seismic instruments for the next several months. The reality is that geophysicists need not only be good in geology and physics but also have good computing and data management skills, and be aware of the IT demands needed by their instruments.

The R/V Marcus G Langseth is well equipped with on-board IT facilities, providing various backup storage and operational systems in place. In this regards, the demands for this expedition are on the lower end of what the Langseth is capable of.

The data servers on board the R/V Marcus G Lansegth.
The data servers on board the R/V Marcus G Lansegth.

The reality is that geophysicists need not only be good in geology and physics but also have good computing and data management skills, and be aware of the IT demands needed by their instruments.

The intriguing task of naming stations

Following a thoughtful group effort they preferred naming the instruments in honor of fish

The intriguing task of naming stations
The intriguing task of naming stations

Usually seismic (and MT) stations would be given some meaningful code such as the name of the local area. Here the scientific group gave the station names helpful codes that indicate the order of deployment and the type of instrument. However, the technical group thought of it other ways. Following a thoughtful group effort they preferred naming the instruments in honor of fish. They also seem to enjoy crossing the names out once the ‘fish’ is in the water.

Past the half-way mark

Out of 39 sites 20 are complete with the ocean bottom stations already recording data.

After 11 days at sea we have passed the halfway mark, i.e., deployed half of the intended stations. Deployments are now proceeding smoother than we have started. We have all become familiar with the procedure of putting an instrument into the water, and it has become a well-timed routine. Out of 39 sites, 20 are complete with the ocean bottom stations already recording data, and will remain there for next couple of months.

Here is a map of the stations deployed so far and the remaining stations to be deployed in the coming days. The map shows a wealth of information about the area known as St Paul and Romanche Fracture Zones across the mid-Atlantic Ridge. The different shaded ocean bottom shows the depth-varying bathymetry; red shade indicates shallow water (still deeper than 1,500 m) – mostly at the ridge and along the fracture zones. The thin, black, numbered lines are age contours in million years from the present. The black dots are earthquakes. Larger magnitude earthquakes are marked in red stars. The various coloured symbols indicate deployment sites. Green checked marks are the current completed sites.

Map showing the stations deployed so far and the remaining stations to be deployed in the coming days. The map shows a wealth of information about the area known as St Paul and Romanche Fracture Zones across the mid-Atlantic Ridge. The different shaded ocean bottom shows the depth-varying bathymetry; red shade indicates shallow water (still deeper than 1,500 m) - mostly at the ridge and along the fracture zones. The thin, black, numbered lines are age contours in million years from the present. The black dots are earthquakes. Larger magnitude earthquakes are marked in red stars. The various coloured symbols indicate deployment sites. Green checked marks are the present completed sites.
Map showing the stations deployed so far and the remaining stations to be deployed in the coming days. The map shows a wealth of information about the area known as St Paul and Romanche Fracture Zones across the mid-Atlantic Ridge. The different shaded ocean bottom shows the depth-varying bathymetry; red shade indicates shallow water (still deeper than 1,500 m) – mostly at the ridge and along the fracture zones. The thin, black, numbered lines are age contours in million years from the present. The black dots are earthquakes. Larger magnitude earthquakes are marked in red stars. The various coloured symbols indicate deployment sites. Green checked marks are the current completed sites.

Inside a floating geophysics laboratory

Basically, this is where and how we spend our days here.

When out at sea for a long time such as the journey we are on, one has to prepare for all necessities related to the purpose of the mission. The research vessel Marcus G Langseth has a number of on board laboratories and computing facilities for us to use. Basically, this is where and how we spend our days here. The different groups prepare the instruments for their upcoming deployments. The instruments consist of various components such as sensors, data loggers and communication devices. After each component is configured and tested, it is then assembled together. This process can take a few hours of preparation. These labs are well equipped with hardware tools that might come in handy at times, as well as coffee machines to keep everyone sane.

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This is the dry lab, the most popular laboratory (probably because it is the closest to the galley). In the picture left to right: Jacob Perez, Daniel Bassett, Ernie Aaron and Sean McPeak.
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The wet lab. As the name implies expect to get yourself and your equipment wet here. This laboratory has direct access to the deck and thus the sea (background).
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The port lab: This lab is currently used to set up ocean bottom seismometers. In the picture left to right: John Clapp, Carlos Becerril and Ted Koczynski.
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The port lab: This lab is currently used to set up ocean bottom seismometers. In the picture left to right: Romuald Daniel and Simon Besancon.
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The main lab: The planning and coordination of the mission is led from here.
In the picture left to right: Robert Koprowski, Tina Thomas, Matthew Agius, Nicholas Harmon and Alan Thompson.