Collecting seismic on land at sea... is one better??

Did you know that you can collect the same kind of data on land too? 

By Matt Griffiths

Just head straight for 6 km and you'll reach the end of the streamers - marine seismic collection happens on a large scale!

Dear Blogosphere,

Matt Griffiths writing and this is day 23 aboard the Langseth. I now have 23 days of experience doing marine seismic. For some background, I just finished a Masters doing seismic processing of near-surface reflection data on land. It has been interesting being apart of the Axial cruise and seeing the similarities and differences between marine & land seismic.

Firstly, in both cases the reflections are pretty hyperbolic. But holy lord there are a lot of diffractions in this marine data; the seafloor of Axial is rough! On land I have been spoiled with bedded clays with beautifully continuous reflections.

The other difference is the scale of the operation. Marine seismic is enormous compared to near-surface seismic. When we were spooling out ~24km of streamers, with 360 degree view of the ocean deep you can't help but contemplate the vastness of the world. And it's just a tiny blue dot in the universe. Being at sea I finally understand why it's a blue dot. Near-surface seismic would have you think that the world is a green or brown dot.

A similarity is the exciting monotony of data acquisition. With every shot gathered we are one step closer to finding some treasure; be it a magma chamber or some actual treasure. It doesn't matter if it is marine or terrestrial, the suspense just builds and builds until you first see the freshly processed section.

Both settings for seismic have their dangers. Acquiring near-surface data using the land-streamer & Microvibe (See Figure 1. -- Details in Pugin, 2013), you have to keep watching out for cars and poison ivy. At sea you have to be watching out for tripping hazards to avoid falling down the stairs or falling overboard.

Although the environments are very different, the physics and fun are the same. If you like doing seismic on land, I highly recommend you try seismic at sea. The inverse is true as well.

Peace be with you,
Matt


Pugin, A. J.-M.; Pullan, S. E., and Hunter, J. A. Shear-wave high-resolution seismic reflection in Ottawa and Quebec City, Canada. The Leading Edge, 32(3):250–255, Mar 2013
doi: 10.1190/tle32030250.1.

The 3rd study Objective: The Axial Jigsaw Puzzle

Objective 3: Putting all of the pieces together

Locations of the recent lava flows at Axial volcano and our 3D survey area over the volcano's summit

The 3^rd objective of our study is to connect the new findings with the massive amount of existing studies! The suite of existing data, which includes continual monitoring of eruptions and earthquakes along with the monitoring of the locations of hydrothermal venting, gives a very detailed backdrop for this study. 

By using 3D data, we can understand more intricate details of how melt fraction (objective 1) correlates where venting occurs.

By taking the detailed information of what is happening on the seafloor, and combining it with details about magma melt and chamber locations, we can gain understanding on how magma chamber properties relate to surface vents!

Where is magma located beneath the different vents at the volcano? These older seismic lines gave us a first order understanding of the melt systems beneath Axial.

There are a number or vents in the region of Axial volcano, by combining the 3D imagery with the existing studies we can see what type of chamber is under each vent.

However, even with all of our new 3D and 2D data collected from this survey, the story is far from over. The new data will provide with us new and better constrained insights into the magma systems and how they relate to recent and, possibly, future eruptions of ava at Axial Volcano.

The second objective of the study!

Objective #2:

By Annie Kell

Lines on the seafloor highlight seafloor features in the vicinity of a seismic line through Axial caldera, such as: fractures, ridges, caldera walls, lava units. Black lines on seismic section are possible uppercrustal faults.

The second objective of AXIAL3D is to understand how the fractures connect to the magma bodies. The presence of fractures in a volcanic setting is not unusual. Many other volcanic systems have similar fractures that form paths between magma chambers. The fractures are thought to be caused by several different processes, and we want to know more about the cause.

Expansion and deflation of the magma body or spreading of the magma body can cause fractures. When magma enters a storage chamber, the pressure and stresses on the nearby rocks changes. Subsequently, when the magma evacuates that chamber, the weakened rock will break into fractures. As this process is repeated the surrounding rocks are weakened and result in cracks that extend from the magma bodies to the surface of the ocean floor. 

Think about a cake that rises too much while in the oven. The over inflation on the top of the cake weakens the cake, and then when it cools and collapses the surface is covered in cracks.

Similarly, when the location of the magma chamber moves (so the location and amount of the inflation moves around), stresses are placed on the surrounding rocks, expanding the area and then forming fractures after collapse.

The various types of fractures seen from existing 2D imagery on Axial volcano are comparable to those seen in systems globally. Axial, however, is more heavily monitored and, with this 3D survey, will be more accurately imaged than most other analogues. By collecting these data, we gain information to test a series of hypothesis for what causes the fractures and what role they play in the volcano dynamics.

The two specific hypotheses that will be tested using the processed data are 1) is the fracturing caused by magma intrusion/motion into the main magma reservoir or 2) is the fracture network attributed to the motion within the more secondary reservoir? 

Because the fractures change the physical properties (things like porosity and how easily fluids flow) within the caldera and the rocks surrounding the system, the physical changes play a role in how exactly the magma migrates. It’s feedback system! The magma creates the fractures, the fractures change the physical properties of the volcano, that dictates where the magma flows which leads to more fractures and so on! 

We want to know if the changing fracture network plays a part of the intrusion events that are far from the main magma reservoir. Also, could hydrothermal venting cause the fractures? Lastly, what types of differences are there in the structure across the region? The findings of this study will help to answer these questions. 

This image comes from Stewart and Davies, 2006. A concentric ring of faults surrounding a mid subvolcanic caldera. (a) This map of the concentric ring faults is based on the disruption of shallow seismic reflection amplitudes from earlier seismic studies.  The second objective of AXIAL3D is to understand how these fractures correlate with the various magma chambers within the entire system.

The second main objective of AXIAL3D is to address the fundamental questions about diking and the correlation of fractures to the secondary magma reservoirs within the Axial system.

Modeling this summer's line of Marcus Langseth jackets...

Our students are feeling right at home with their new jackets and coffee mugs!

By Sam Mitchell

Tanner, Morgane and Michelle model the latest line of Marcus G. Langseth gear in the main lab

One of the benefits of doing science at sea is picking up souvenirs and memories from every vessel and expedition that you go on. For many of our students, this was their first opportunity to get their hands on some ship memorabilia...

Science looks all the more serious when you have the matching jackets...

So when the captain opened up the shop, there was a Black-Friday-esque rush to try on the latest and greatest fashion for 300 miles around - Lamont's very own Marcus G. Langseth gear! A few minutes later, Michelle, Morgane and Tanner were ready to show of their new purchases in a variety of settings and moods.

Balloons and attitude... "Are you cool enough to wear our jackets?!"

Everyone was apparently jealous of this new style, so when the captain re-opened the store a week later, there was once again a dash to pick up T-shirt, jackets, caps, water bottles and even STICKERS! It's fair to say that everyone is now well-kitted out with their new ship apparel. We hope to get a group photo of everyone wearing their gear once this is all done and everyone is on the same schedule!

All in all, they seem pretty happy with their purchase!

Meet the Science Party! Axelle Cap

Hello all, my name is Axelle and I am a graduate from a Master in Marine Geosciences in Brest

WHAT IS YOUR AREA OF RESEARCH?

My research is in paleoclimatology and sedimentology

WHAT IS A FIRST TIME FOR YOU ON THIS EXPEDITION?

This is my first time on a cruise ship. I have never been on a cruise ship, only on sailing boats for hobbies.

WHAT ARE YOU EXCITED TO LEARN/DISCOVER?

I am excited to: discover the life and rhythm on a scientific cruise ship, learn how to process seismic data, see the seismic equipment deployment, and to meet whales!

WHAT DO YOU LOVE ABOUT MARINE SCIENCE?

I love that we can explore the most unknown domain on earth.

TELL US SOMETHING ABOUT YOURSELF

I live in Brest (the best and most-western French city!). I also love hiking, sailing and biking.

Life At Sea 101 with Brian!

So you signed up for a research cruise and here you are: day number one and we are underway. I guess by now you’ve realized the learning curve extends a bit past the science and equipment.... 

By Brian Oller

Nothing out here is quite like what you left back home, including the lingo used aboard the ship. Don’t worry, I’ve been on a few research cruises now, and I served aboard a few U.S. Navy vessels when I was in the military, so I have this stuff down. I’ll get you started with the basics. There’s more to learn than what’s covered here, but this will at least get you to the right place at the right time. 

Getting around

The first bits of bazaar lingo you notice is the standard directions are no longer in play. Words such as left, right, front, and back were left ashore alongside your soy latte and memory foam mattress. Left and right are now port and starboard, respectively. These are important words because port or starboard side designates the location of much of the equipment you’ll be using. Now that you can find your way laterally about the ship let’s work on the front and back. If you’re told to meet at the bow, you’re being directed toward the front of the ship (that’s the pointy end if you’re still a little confused). Likewise, the back of the ship is called the stern. This is where the propellers are located, but we don’t call those propellers, we call them screws. If you don’t need to be as specific use forward (self explanatory), and aft. These terms usually describe rooms or areas within the ship. For example: “We’re keeping the bags of coffee in the forward wet lab. Grab some on your way back from the mess deck, we’re running low.” Note: ships run on diesel, oceanographers run on coffee. We’ve also run across a new term, in this case a critically important place, so I’ll keep moving.

Places to go

Now that you know how to get around, you may be interested in where to go. Back to the mess deck, this is simply the dining room. Similar to a small dining hall in your campus dormitory, this place harbors one distinct difference: the food is actually better! That’s right, better. Science at sea is inherently more difficult than ashore. Experiments go sideways and gear breaks down all the time, but a good meal can set all right with the world. I might as well mention the galley while we’re here. This is the kitchen where the cook and stewards prepare four meals a day plus plenty of snacks. The men and women that work here are as mission-critical as anyone or anything aboard. They can make a bad day go away faster than a couple pints of beer! Moving on, there’s the bridge. Star Trek fans should be familiar with this place. Like the movies and TV shows, this the nerve center of the ship, you’ll find the Captain and mates up here. From this perch atop the ship they steer, navigate, communicate, and keep a look-out. The bridge is all business 24/7, so don’t come in without an invitation. I’d be remiss if I didn’t mention the head, a.k.a. restroom. There are a few of these aboard ship but we all have to share, so be polite and keep ‘em clean.

Things you encounter along the way

Continuing on the topic of getting around, new names for common fixtures and conduits are probably worth a mention. We touched on this earlier so let’s break down the deck a little further. Anything floor related is called the deck. Like a building with multiple floors, ships have multiple decks. The naming convention may vary slightly from ship to ship, but some examples aboard the R/V Langseth are A deck, B deck, main deck. Sometimes they’re referred to according to the equipment installed on the deck, such as the streamer deck, paravane deck, or gun deck (no, not those kind of guns, we’re unarmed). “Deck” can be used in a very localized sense, the same as you would use “floor,” for instance, “Let’s get these boxes picked up off the deck.” Making your way around the ship you will make extensive use of passageways. A passageway is just a hallway but here they’re pretty narrow, so we have a bit of edict we utilize when passing one another in opposing directions. Sound complicated? Don’t worry, you’ll have it sorted in no time. As you move down the passageway you’ll certainly encounter a ladder well. This is just a staircase, but again a little narrower and a little steeper that what you’re accustom. Be sure and grab a handrail until you get your sea legs, getting tossed down a ladder well is no fun. Be patient, your sea legs will turn up in a couple days.

Motion of the ocean

Speaking of sea legs, let’s talk about how the ship moves around out on the open ocean. This is also a good chance to try out some of our new vocabulary. The up, down and side to side motion is described by three terms. First is pitch, that’s a rocking motion from bow to stern. Next is roll, that one rocks the boat side to side, or port/starboard. Roll bounces you around the passageway like a pinball, but it can also make for great sleep. The combination of pitch and roll is heave. This is just the general up and down movement, which we keep careful note of to calibrate some of our instrumentation. The ship has sensors installed to help us monitor all the motion accurately, but if you look around you will probably find some work spaces adorned with ”locally manufactured monitoring devices.”

What the hell time is it anyway?

Guess what, telling time, that life skill you thought you had mastered, that’s a bit different as well. An ocean-going vessel is a 24 hour a day operation, so it’s much easier to remove the ambiguity of AM and PM. Frankly, I think the 24 hour clock should be used ashore as well, 24 hours in a day, 24 hours on a clock. This isn’t difficult to work out, but it does take a little while to develop an intuition. If dinner is served from 1700 to 1800, what does that mean? Don’t be afraid to count on your fingers, your time intuition usually turns up about the same time as your sea legs. Of course, you may be assigned to the night shift, which will take a little more getting used to both in terms of time and the night creatures themselves, like me. Night crew might be a little weird, but we’re a lot more fun! However, that’s another story.


It’s totally normal to feel a little confused, a little weary, and maybe a little sick when you first step on board, but that all goes away after a few days. The work you do and the people you meet while you’re here will stick with you for a lifetime. Enjoy your time out here, not many scientists get the opportunity to go to sea and if you have any questions about the nomenclature, don’t be afraid to ask....

Meet the Science Party! Brian Oller

I'm Brian Oller, and I am a PhD student at Scripps Institution of Oceanography in sunny San Diego, California, USA. I began this adventure in the small town of Levelland, Texas at South Plains College.

WHAT IS YOUR AREA OF RESEARCH?
I’m a rock hunter at heart. I apply geochemical and isotopic systematics to interpret tectonic processes. My broad focus is concerned with the evolution of the western North American margin. My research sites are the Sierra Nevada mountain range and associated Walker Lane/Eastern California Shear Zone, the California Coast Range Ophiolite, and I have recently submitted a manuscript discussing isotopic, geochemical, and tectonic evidence of continental lithosphere formation from oceanic lithosphere parent beneath the Ferrel Seamount off the coast of Baja California, Mexico.

WHAT IS A FIRST TIME FOR YOU ON THIS EXPEDITION?
3rd scientific research cruise (R/V Tommy Thompson, R/V Sally Ride), first 3d seismic cruise, first time collecting and processing 3D seismic data, first time to sail Puget Sound and JdF Straight.

WHAT ARE YOU MOST EXCITED TO LEARN/DISCOVER?
I enjoy tinkering with almost any kind of equipment or gear, so I look forward to getting some “hands on” time with a large 3D array. It’s always fun to collect data and assemble it to tell a story or paint a picture, so as the trip progresses I look forward piecing together the data set and seeing how it develops.

WHY DO YOU LOVE MARINE SCIENCE / GEOSCIENCE?
It provides the opportunity for me to go places I may never have had the chance (or inclination) to visit, such as the Canary Islands. More often than not my travels take me well off the beaten path, away from major population/tourist centers, to enclaves that most people don’t know exist. To top it off, I get to go to sea. To many people, spending weeks on a boat sounds insane. Maybe so, but I’ll ask this: Do you know what color blue the ocean is 500 km from shore? Have you ever seen a full moon rise over a dead calm sea? How about a star lit sky on a moonless night, hundreds of miles from the nearest street light? That’s why I keep coming back, and that’s why I love geoscience.

TELL US SOMETHING ABOUT YOURSELF!
I’m a USMC veteran, served in Iraq, and started and operated a residential remodeling business in Texas before starting undergraduate studies and moving on to a PhD program.