Sunday, August 2, 2015

2000 “Texans” with all the fixin’s….

During our project, we plan to record sound waves generated by a series of controlled blasts on two profiles, one with 2000 instruments (“Texans”) deployed along a 350-mile-long profile across Georgia and another with 700 Texans deployed along an 80-mile-long profile.  In total, that’s 2000 instruments and 2700 deployments!! Lot of instruments means lots of stuff.   The basic components of the instruments themselves were shipped in ~160 big plastic boxes arranged into ~18 pallets.  Each of these instruments will be powered by two D-cell batteries. To power the instruments for both lines, we needed 5500 D-cell batteries.  We picked them up from the Lowes in Vidalia as a 2000-lb pallet.  For each station, we also need flags to mark the locations, and bags and tape to protect the data recorder.  We very quickly filled up our 1800-square-foot field center in Lyons, GA with all these goodies…

Donna Shillington,  LDEO

Freshly delivered pallets of boxes holding all the science equipment

The PASSCAL team re-arranged the boxes into a T for their own devious reasons :)
The trusty Silverado loaded down with 2000 pounds of batteries! (Dan for scale).




Friday, July 31, 2015

Drill, Baby Drill! Drilling and filling for the SUGAR seismic shots

We are using sound waves to image the subsurface of Georgia along two long transects.  It is like creating a huge x-ray of the geology in the region. Thousands of instruments (termed “Texans”) will record sound waves that are generated from a series of controlled seismic sources (“shots”) that we will set off along the line. 

For the last few weeks, the seismic source team, based at the University of Texas – El Paso, and the drillers have been hard at work drilling twenty-six 60- to 100-foot-deep holes that will contain the explosives used to create the sound waves.  Once the holes are drilled (the first stage of which is termed spudding), emulsion explosives with boosters and caps are carefully installed in the base of the hole and the remaining height is filled in with dirt and gravel (“stemming”). 

Now with the 26 shots drilled and patiently waiting for the electronic signal to blow, all we have left to do is deploy the 2,000 instruments that will record the sound waves … An easy feat for the 50+ scientists, students, and engineers descending on Vidalia, GA over the next few days.  Stay tuned for our progress and adventures as we continue on this epic scientific undertaking.

Natalie Accardo - LDEO

The SUGAR seismic source and science team from left to right:
Steve Harder, Dan Lizarralde, Ashley Nauer, and Galen Kaip
The drill rig set up and drilling a shot on SUGAR Line 2.

Galen Kaip prepares the source charges (white tubes) on the truck bed as
the drillers complete a shot hole.

The source team carefully lowers the prepared seismic charges into the complete shot hole.
Ashley Nauer (red hat) stands waiting with shovel in hand to fill the remaining height of
the hole with sand and gravel.   

The drill team monitors the process of spudding, the very first stage of drilling the
shot hole, for SUGAR line 2.

The source team and drill team push on late into the night to ensure the completion of the
final shot for the entire SUGAR experiment.  

Tuesday, July 28, 2015

Ramping up for bigger, badder SUGAR Part 2

We are in Georgia gearing up for the second phase of field work for the SUGAR project, which will involve collecting seismic refraction data along two profiles spanning eastern Georgia. In the coming weeks, we’ll deploy thousands of small seismometers along county and state roads across the region, which will record sound waves generated by a series of controlled blasts. We can use the sound waves to make pictures of geology beneath the surface. Geological structures beneath Georgia record the most profound events involved in the formation and evolution of the eastern North America continent. In particular, we want to image an ancient suture between Africa and North America that formed when these continents collided to create the supercontinent Pangea, frozen magma bodies from one of the biggest volcanic outpourings in Earth’s history, and continental stretching and thinning that lead to the breakup of Pangea and formation of the Atlantic Ocean.


Map of SUGAR lines, showing two possible locations of the ancient suture (red dotted lines)

We collected similar data in western Georgia last year during the first phase of the SUGAR experiment imaging these same features. During that field program, we deployed 1200 seismometers and set off 11 controlled blasts along a 250-mile-long line, which felt like a big project at the time. But this year, we will go even bigger! In eastern Georgia, we need to span an even larger area to encompass our geological targets. One of the reasons that we need to look at a bigger swath of the earth is that there is a debate about the location of the suture here – it could be as far north as Milledgeville, GA or as far south as Baxley, GA. (In case you are not up on your Georgia geography, those towns are ~100 miles apart). This means longer profiles, more instruments and more blasts! We will deploy a total of 2700 seismometers and detonate 26 blasts along two profiles. The longer profile spans 350 miles from Winder, GA to the Florida-Georgia state line near St Mary’s Georgia. Stay tuned!

Donna Shillington, LDEO 



Wednesday, July 22, 2015

Stay Tuned for SUGAR 2!!

In just a few short weeks a mass of students and scientists will descend on southern Georgia with work boots and sunscreen in hand to take part in the second portion of the SUGAR active source experiment.  Make sure to stay tuned for regular updates on our progress and to learn more about the exciting science that motivates this amazing field expedition!

Tuesday, March 25, 2014

Long lines and lots of instruments

If you want to image the Earth’s crust and upper mantle with seismic data, you need to record the arrival of seismic waves that have propagated down to, in our case, depths of up to ~30 km.  These deep-diving phases travel quickly through the denser, higher velocity rocks of the lower crust and upper mantle, and they arrive back at the surface ahead of shallower phases at long source-receiver offsets (see video below).  


video


To record these lower-crustal and upper-mantle phases as “first arrivals”, where they are not obscured by the arrival of energy from shallow paths, we use long lines.  Long lines mean lots of receivers and lots of driving to deploy and recover these instruments.  We could have used lots of sources instead, but the blasts we used to get seismic energy into the lower crust and upper mantle in this experiment take a lot of time and money to setup.  Receivers are much cheaper, so we used a lot of them.  (For similar wide-angle/long-offset work at sea, airgun sources are cheaper than putting seismometers on the seafloor, so we use many shots and a smaller number of receivers out there.)


This time-lapse video shows Team 13 of 14 recovering 89 of the 1200 total short-period seismograph stations from where our line crossed Fort Benning, near the northwestern end of the line.



Nathan Miller, LDEO


Deploy in the rain, recover in the sunshine…



Weather map during deployment.
When the time came to install our 1200 small seismographs across Georgia at the flagged positions, the rains came….   A lot of rain.  During our first deployment day, we received 1-2 inches of rain, and another wave of rain clouds came through on Day 2 (check out map). Roads that used to be easily passable became mudholes or were flooded with water. All-wheel-drive vehicles and drill rigs alike got stuck, and a few station locations could only be reached on foot. Our hard-working field crew labored in the rain digging holes and deploying seismometers.  Vehicles, equipment and people were covered in the famous Georgia red clay (and other muds and sands of Georgia and northernmost Florida). Adding insult to injury, problems with the programming of some of the instruments meant that we actually had to pick up and redeploy many of them. It was a mudbath.  Nonetheless, our field crew managed to deploy 1200 seismometers across Georgia by Tuesday at sundown. It was an impressive show of endurance, and an inspiring display of positivity given the number of people that were still smiling and upbeat at the end of it all. 
A couple of days later, after our seismic shots, it was already time to pick up the instruments, and the weather changed completely.  The sun shined on SW Georgia, and we picked up almost every last seismometer in just one day under blue skies….  
Donna Shillington, LDEO

Wednesday, March 19, 2014

Random Pictures from the Road (and otherwise)

As a follow follow up to Chastity's post, I thought a few random pictures from the road would be entertaining. I have been part of group 5 and as such responsible for the part of the line that spans from Hahira in the south to just north of Adel.

 
South-central part of the seismic line. The yellow line is team 5's section. 
We have been in a relatively rural part of Georgia and as a result have not encountered many locals save a few who have stopped to ask if we are ok. However, we have seen quite a few interesting things that are quite out of the ordinary (to me at least).

Friendly Muscovy duck.
Rocks in a stream bed with associated pink spongy material (?)

Spanish moss.
Linguoid (current) ripples on a washed out road.
 We have also seen quite a few old abandoned farm houses in various stages of aging...



At least 10-15 dogs were standing guard at this house, including about 8 puppies.

Caroline making some new friends.

All said we have dug 122 holes in team 5's stretch. We have also helped deploy instruments in other sections as well and while doing so have seen others hard at work.

Meghan and Nate getting it done!
Along the way the cars have taken quite a beating and have actually held up pretty well. Although there have been a few instances where people got stuck, I think that the people with the toughest job will be the guys that have to detail the cars upon their return...



A more appropriate vehicle (?)
And lastly here's a couple more random pictures that I thought were interesting.

The large disparity in fuel grade gas prices.

A ~perfectly leveled geophone (it's harder than you'd think).
Hopefully this random selection of pictures was entertaining. Up next we will post about last night's "shots." In the meantime, I can say that they were all successful with varying degrees of excitement. The most important thing is that all of our hard work is being realized as the instruments are recording refractions from buried geology that will help us unravel some of the mystery that surrounds events that happened in this area long ago.

James Gibson, LDEO