Saturday, July 31, 2010

Some observations on some of the data collected thus far

Before we get to the science, a brief introduction of myself. My name is Dan'l Lewis and I am a new Master's student at Texas A&M University in the Department of Oceanography. My areas of interest are marine geology, geophysics, and plate tectonics and my fields of interest in particular is seismic interpretation of marine geology. I am on this cruise courtesy of my advisor, Will Sager, and two more of his students, Sam and Chris. A big thank you for the invite to come along.
That being said I will now move to the science. As we have traveled from Hawaii to the rise we have taken numerous measurements at regularly spaced intervals. As we are still shooting, the refraction lines it will still be several days before we can begin processing any seismic reflection lines. In the meantime, I have compiled a few charts of data as we progress westward across the Pacific towards Shatsky Rise and these data will continue to be collected throughout the process. The data I will talk briefly of today in particular is temperature versus latitude and temperature versus longitude. Unfortunately I could not grab the plots before this post was made and I will try to add them at a later date. It is noticed that there is an increasing trend as one moves from east to west across the western Pacific. The temperature also fluctuated but I assumed some of that was daily heating and cooling. However, as we have progressed westward at several points we hit areas of far colder water than the surrounding waters. Our time through these cold eddies is brief maybe an hour at most but it is of interest that there is almost a degree of difference in water temperature. It may not seem like much but if you compare it to the human body temperature, raising or lowering a few degrees can have quite an impact. I'm not sure what exactly these cold spots are and what there relation to currents throughout the Pacific are, but hopefully as my studies in Oceanography progress, I can shed some light on them. Or perhaps someone can enlighten me with why there are these cold upwellings in seemingly random places. Once again, I apologize for not posting the chart, but I will try to post it as soon as possible.

*edit* They are up now. The data is organized such that it matches the track i.e. the right side of the chart is Hawaii and the left side is Shatsky Rise. I believe the negative spike in the data on the right was us coming off of the Hawaiian Swell. Also to note is the longitude values are based around 0. Excel was not smart enough to allow 180 to be a center value and my GMT skills are lacking, but the image produced still gets the point across. Again apologies for the delay.

Friday, July 30, 2010

Sunset on the sea

I am Kai Gao, a Ph.D. graduate student from the Department of Geology and Geophysics at Texas A&M University. I joined TAMU G&G last August and now I am working with Dr. Gibson on exploration seismology. My current research is mainly about the velocity-confining pressure relationship for cracked rocks. Basically, I am developing a set of equations describing how the P- and S-wave velocities change of different cracked rocks under confiniing pressure, and do corresponding cracks parameters (e.g,, crack density, matrix velocity, etc.) inversions if given experiment data of pressure-velocity. According to the current results I got, this relation is neither linear nor simple nonlinear, it can be approximated by power-law-based square-root relation. Anyway, perhaps you can see my results someday in some journal. I also hope that will not be too far away.

Shifting to the Shatsky cruise, we have finished dropping OBSs on predesigned sites across Shatsky Rise and now we are implementing over 1000 air gun shootings along the first line (in fact it includes a long seismic line nearly NW-SE and a short line perpendicular with it), and we expect to finish the shooting tomorrow, and then Langseth will utilize streamers along with air guns to explore several other seismic lines over different regions of Shatsky Rise. It is exciting that this is the first time that human beings can detect deeply inside this supervolcano other than merely understanding the shallow sediments. See a detailed report from Oceanography TAMU.

This vast ocean is never mean to bequeath its pulchritude in the endless time. Every moment is its never-returning past, every moment is its ever-extending verve to the future, even when the sunset is coming and try to cover the ocean with black night. The sunset itself is an evanesce, while it is an undying dazzling impression for me, just like an opera performed by the sun and our earth.

Thursday, July 29, 2010

Intro to MMO ( Marine Mammal Observers)

I guess you may not know there is someone studying animals on our seismic survey ship. Animals and seismics? What relationship? Actually, they have. And they have much more power than you could expect. The marine animal folks have the right to stop our seismic survey at any time when applicable. Who are they? Let me introduce to Marine Mammal Observers (MMO).
Marine seismic survey requires the transmission of strong acoustic pulses into the water, done by suddenly releasing compressed air from an array of air-guns. Although the acoustic energy attenuates with increasing distance down to the seafloor or horizontally spreading, some of the pulses are still strong enough to be detected by marine mammals and other marine animals at distance of about 50-100 km, and have potential to disturb them like whales in the study area. And disturbance events will result when marine mammals or sea turtles near the seismic activities are close enough that they might experience temporary reduction in their hearing sensitivity or react behaviorally to the sounds generated. That is why MMOs show up during our seismic cruise, under the U.S. Marine Mammal Protection Art (MMPA) to minimize the disturbance of marine mammals. However, no serious injury and/or death is anticipated fortunately. (More information)
Pictures shown here are the observing station on the very top of the boat and one of the MMO group watching carefully with 'Big Eye' equipment to make sure no marine mammals appear within potential disturbing distance. If not! They will call stop the air-gun shooting, and all of us are forced to have a break.

Tuesday, July 27, 2010

My new found respect for seismic data

Me in the orange helmet with the WHOI deployment team
Hello everyone and welcome back to the Shatsky blog. It's my post today, and I'll do a quick introduction. I am Tolulope Olugboji, an international graduate student at Yale University. I work with Jun Korenaga (chief scientist on this research cruise), and my research work so far has involved using seismic data to study the crustal structure and origin of large under-sea super volcanoes. This involves me processing seismic data and using these data with inversion techniques to create images of the crust underneath the ocean sea floor. This procedure is known as tomography. Yea, I know, I tried to be brief.

Now that you know me, I have exciting updates from the Shatsky cruise. One is that I finally got my sea legs! This is a big deal for me, because if my body hadn't adjusted to the constant motion of the sea, I would have missed all the action that started yesterday on the Langseth. The high point was when I got to launch the very first ocean bottom seismometers (OBS) to be used for the tomographic imaging of the Shatsky crust. It was also a very important educational experience because it made me realize the value of seismic data. I have worked with seismic data for a while now, but I never appreciated the whole process that goes into acquiring the data.

Each OBS launch requires the participation of almost everyone on the ship. The navigation crew, the main lab, the deployment team and I am sure some other crew members that I still don't know about. The process is delicate and technical. The precision, organization, teamwork and time needed for deployment and recovery has given me a new found respect for seismic data. My take home message: learning about Earth's history and inner workings takes the dedication and commitment of a lot of people. Kudos to everyone on the Langseth. I promise to treat our data well.

Monday, July 26, 2010

One last look... then we drop 'em

To the left is a view of the combined ocean bottom seismometers and hydrophones (OBS) resting comfortably in the OBSIP shack on the deck of the R/V Marcus Langseth. OBSIP is the U.S. National Ocean Bottom Seismometer Instrument Pool. The particular instruments that we'll be using are from Wood's Hole Oceanographic Institution.

Each instrument is comprised of a short-period three-component geophone and a single hydrophone. As shown in the cartoon below (credit: WHOI), after the OBS hits the seafloor, the wire to the geophone burns over a few hours and the geophone drops to the seafloor at a distance from the main instrument housing to minimize noise. The hydrophone is positioned at the top of the plastic housing. Later, when it comes time to pick up the OBSs, we'll send a signal to each instrument to release from the bottom. Then they'll float to the water surface, and we'll pick them up.

OBS deployment will start soon...

Nine days after the departure at Honolulu, we are finally arriving at our survey area. In about an hour, we will start deploying ocean bottom seismometers, 28 in total. Will Sager noted me that this transit was like biking across the United States. A very good analogy indeed, as we've been sailing at 10-11 knots (which is about 12 miles per hour). See the map above to feel the scale. You can also see that the Shatsky Rise is about the same size of California. We'll be spending the next 32 days to study this massive volcanic feature by active-source seismology.

Sunday, July 25, 2010

My Life as a Student Volunteer

Hey there, it's Kelly Brooks here, enjoying another sunny day aboard the R/V Marcus Langseth in the middle of the Pacific Ocean. Although I have spent many a day on the sea in a boat, the majority of it has been only in the Gulf of Mexico for short seismic jaunts or fishing trips with my grandfather. This excursion, practically clear across the Pacific, obviously takes the cake. So far we have been at sea for 1 week and have around 6 weeks to go. We should be arriving at our study area tomorrow night to begin data acquisition. First, we will be deploying OBS's (Ocean Bottom Seismometer) to obtain seismic refraction data. We will then start the process of "mowing the lawn" using an air gun source and streamers to collect seismic reflection data. As a student volunteer, this cruise presents an amazing opportunity to get hands-on training in seismic data acquisition and processing. At the end, each one of us should be well acquainted with operating systems like Linux, seismic interpretation software like Promax, and the handy tools of GMT which aid in creating study area maps essential for research papers. So, I thank NSF for funding this unique journey to one of the oldest oceanic plateaus in the world and allowing this incredible, skill-building opportunity. Tune in again next week for the beginning of crew profiles where I will conduct short interviews to find out about what their roles are on this ship.

Friday, July 23, 2010

MGL1004: Why we're here

Nobody hasn't explained yet what this cruise is all about, so here it is. We're heading to the Shatsky Rise in the western Pacific, which is a massive oceanic plateau (or a "supervolcano" if you watch BBC), and we're going to investigate its crustal structure to understand how this plateau formed and why. The origin of this plateau has been mysterious and controversial as well, and resolving it has many important implications for how Earth's mantle works (I'll write about them later).

How do we study the crustal structure? We'll use big artificial seismic sources generated by an array of "air guns" and listen to how seismic waves propagate to reconstruct the subsurface structure. We'll use both multichannel seismic (MCS) profiling, which gives us a detailed image of the upper crust, and ocean bottom seismometers (OBS), with which we can reconstruct the entire crustal structure. We'll spend 32 days in the survey area (called "science days"), and it takes 20 days total to go back and forth between the Shatsky Rise and Honolulu, so our cruise is 52 days long. Yes, this cruise is quite a long one.

This field project is a collaboration between Yale (Jun Korenaga) and Texas A&M (Will Sager), funded by U.S. National Science Foundation. We had one more scientist from Lamont-Doherty Earth Observatory (John Diebold), but unfortunately, and very sadly, John passed away two weeks before the cruise (read an obituary here). We were, however, lucky enough to find a substitute at the very last minute, and Jackie Floyd is onboard to oversee MCS data processing. Besides that, we have seven graduate students (two from Yale and five from TAMU); I'll let them introduce themselves when they make a new post. We also have a science tech group from Lamont, an OBS team from Woods Hole Oceanographic Institution (WHOI), and five marine mammal observers (MMO). Keep reading the blog to find out who they are and what they do!

Somewhere over the rainbow... there's another rainbow.

Here on the R/V Langseth, there is a lot of scenery to take it. Not being familiar with life at sea myself, the most striking feature is the continuous horizontal line that surrounds you that is the unobstructed horizon where the sea meets the sky. The sun rises and sun sets are quite the marvel as well. Every night as we make our way to Shatsky, the sun seems to sink right into the Pacific ahead of us, just to resurrect directly from the ocean behind us the next day. So far we have yet to see a green flash, but we are keeping our fingers crossed. We find ourselves in small and frequent rain storms that scatters the sun's light into magnificent rainbows. We see a rainbow almost everyday. Some times we even see a double rainbow. There has not been much sign of sea life so far in the transit to Shatsky. This is a good thing, being that we must stop using the air guns for a while if marine mammals are spotted while we are shooting. While at the Shatsky Rise, we run a small risk of crossing paths with a typhoon, in which case we have to run for cover until the storm passes. The weather has been pleasant so far and hopefully that remains true for the remainder of the voyage. It is truly a beautiful and humbling experience to be in the middle of Earth's largest ocean and at her mercy.

Greetings from the graveyard shift on the way to the Rise

Greetings and salutations from beyond the Date Line. Yeah that's right. We crossed the IDL. But unlike New Year's Eve there was no ball drop. We did get some sweet certificates though. Crossing the IDL is not a daily thing, however, and that is what I am here to cover.

Daily life here is not quite what I expected, although now that I'm here, I'm not sure what it is that I expected. We're on a 24hour boat. We don't take weekends or holidays. Therefore everyday at sea is like a Monday. Or a Friday. Just take a day. It'll do. My hats off to the guys that run this ship. It runs like clockwork and they do everything they can to keep us comfortable while we work. Big thank you to them. I digress, however. It is relatively simple to adjust to the daily routine that is sea life. What is not as easy to adjust to is the changes you make from your daily routine on land. For me, I would wake up to my phone alarm (which I still do regardless of latitude or longitude) and check my email and the weather. On land. At sea? Scratch the last two things. Also I've learned that roommates on land don't care quite as much about noise. Loud noises during the day in the sleeping areas on a 24 hour boat are a no-no. If you want to be "that guy" on the boat, make loud noise in the sleeping areas at all hours of the day. Also, the times for meals... make sure to make those or you will be eating leftovers... not that those are bad, on the contrary they are quite tasty... Anyway 1) wake up, 2) shower... oh and by the way, stability is something I totally took for granted on land. Basically to do anything you need to have your feet spread about shoulder width apart and orthogonal to the wave action. Otherwise you will end up face down on the floor. No it hasn't happened to me... yet. 3) eat lunch (no I'm not sleeping in, I'm on the night shift), 4) migrate to the science lab and watch way too many monitors at once. 5) monitor monitors for 4 hours 6) enjoy a few hours of leisure time plus dinner, 7) grab a quick nap, 8) midnight to 4am, 9) bed, 10) repeat. While on duty, though, or even off duty you may be called to help the crew with some of their tasks. For example, today I got to help setup the XBT launcher. I was also the "anchor" for the end of some streamer cable i.e. I was tension in the line so it didn't unravel. All things necessary for the advancement of science. I will definitely give an improved update of daily life once we begin shooting the seismic data. I'm sure there will be far more things to pique the readers curiosity. Goodnight and godspeed.

Thursday, July 22, 2010

Passing the International Date Line

We still have 5 or 6 days to arrive at the Shatsky Rise. Life is monochromic on the sea, like the surrounding seawater. Everyday I get up in the morning and go to the main lab, and begin to face a lot of screens, and immerse myself in Fourier Analysis and the never-ending engine noises. Sometimes I will talk with kind Bern and Michael, and Kelly, and that makes the life here not that boring.

Today we passed the International Date Line at noon and entered "the domain of Golden Dragon". I have thought many people, at least a few of them, will celebrate in some way. However nothing happens. I just took several pictures of the GPS navigation screen. There is no 180 00.00000 shown, since after IDL, the latitude itself will decrease. After all, it is memorable, we grew older for a day at that moment. But perhaps it is hard for you to read those numbers. That is, 179 59.94936 E.

In the morning, there appeared a huge rainbow over the sky before the ship far away. I ran back to my cabin, got out of my D90 and ran to the deck, but, it disappeared... Beautiful things never last that long that everyone can reach them. So are our lives. Su Shi (蘇軾), a Chinese poet in the Northern Song (北宋) Dynasty ever wrote in his essay,

"We are mere fishermen and woodcutters, keeping company with fish and prawns and befriending deer. We sail our skiff, frail as a leaf, and toast each other by drinking wine from a gourd. We are nothing but insects who live in this world but one day, mere specks of grain in the vastness of the ocean. I am grieved because our life is so transient, and envy the mighty river which flows on forever. I long to clasp winged fairies and roam freely, or to embrace the bright moon for all eternity. But knowing that this cannot be attained at once, I give vent to my feelings in these notes which pass with the sad breeze. " (況吾與子漁樵于江渚之上,侶魚蝦而友麋鹿,駕一葉之扁舟,舉匏尊以相屬。寄蜉蝣於天地,渺滄海之一粟。哀吾生之須臾,羨長江之無窮。挾飛仙以遨遊,抱明月而長終。知不可乎驟得,托遺響於悲風。)

So whenever you find something beautiful or something worthy to do, try to feel it, or make it.

Wednesday, July 21, 2010

On the Hawaiian swell

Our cruise started from Honolulu, Hawaii, and as it happens, we're sailing along the Hawaiian seamount chain, which is perhaps the most famous hotspot track and has played a very important role in the theory of plate tectonics. You may see in the bathymetric image that seafloor around this seamount chain is a little bit shallow (i.e., blue is lighter), and this topographic feature is known as the Hawaiian swell. The seafloor of this swell is ~500 m shallower than it should be given its age (~80-120 million years old), and the cause of this shallowing is still debated.

At any rate, we'll keep sailing with this heading for five more days or so until we arrive at the Shatsky Rise, our main survey area.

Tuesday, July 20, 2010

Underway Geophysics

Even when we're not at our study site, we're always collecting data at sea on the R/V Langseth. In the old days of Lamont when Maurice Ewing was Director, Lamont ships were required to stop once per day to collect a sediment core and other oceanographic and geophysical data. It was informally called "taking a Ewing," or so I've heard. Today, we only acquire underway data that does not require us to stop during transit. That includes magnetics, gravity, multibeam bathymetry, and 3.5 kHz and 12.0 kHz high-res bathymetric profiles. In addition, each day we take an expendable bathythermograph (XBT) measurement, which provides ocean temperature data down to under 1 km depth. In the image to the left, Chief Acquisition Officer Bern McKiernan and TAMU graduate student Kelly Brooks prepare to drop an XBT off the stern of the R/V Langseth for today's measurement.

My first day on watch

Howdy, it is my first day on watch in the main lab of Langseth. Kind of nervous, because I am afraid of messing things. A lot of monitors I need to watch: GPS, Multi-beam, Sub-bottom scan, and kinds of other systems. Like guys say, when the OBS, streamers and guns are set, we will have much more things to do. So for right now during the transit, it's much easier. Anyway, it is my duty to make sure everything is working well. Keep my eyes on all the monitors, keep updating paper log and elog, draw ship track on trace paper, and sometime help technician do things. However, most of the time, kind of boring, not much things to do, just repeat things. But boring is good. That means everything goes well, no problem to report, no need to fix things. We expect boring even though we do not want to. Boring means good. My shift time is 4-8am and 4-8pm. Not bad, except need to wake up in the early morning. But I am able to enjoy the sunrise and sunset every single day via our video monitors. Awesome!

Monday, July 19, 2010

The Langseth: A moving laboratory

Most science experiments are conducted in stationary laboratories. These experiments in most cases are controlled, and the relevant apparatus is managed in a permanent physical space. Unlike these experiments, the ongoing seismic research survey will be conducted by the Langseth - a moving laboratory.

The ship will be in motion the entire time, sailing towards the Shatsky Rise in order to obtain magnetic, gravity, bathymetry and seismic data. Even now, as the ship sails towards the Shatsky, still 8-9 days away, the Langseth is steadily obtaining sea floor bathymetry, gravity and magnetic data. The science party on board logs these data ever so often. The Laboratory, always moving, is always operational.

Sunday, July 18, 2010

Where are my sea legs?

The Shatsky cruise has finally started. I should originally be excited, taking pictures and posting them right now. However, I still can't handle the feeling of the world moving around while typing on the keyboard. It's a very unnerving feeling. Anyway, as soon as I get my sea legs, I will get to writing exciting updates. For now, I am willing myself to adjust while watching the very impressive feeds on the computer screens in the lab. There is one for every important geophysical device attached to the ship. Impressive technology.

Saturday, July 17, 2010

Cruise finally got started!

At 4:35PM (Hawaii local), R/V Marcus G. Langseth finally started to sail, and we're now underway toward the Shatsky Rise. This transit will take about ten days. Shown here is a view of Diamond Head from the ship as we're getting out of Honolulu.

More on later!