We left Balboa, Panama, on schedule at 10 a.m. on Sunday, July 6. We've now been steaming for 1.5 days and have had great weather with calm seas. There are 42 people on board the R/V Maurice Ewing. There are 19 members of the crew: captain, 1st mate, 2nd mate, 3rd mate, chief engineer, 1st engineer, 2nd engineer, 3rd engineer, boatswain, 2 A/Bs (able-bodied seaman), 1 O/S (ordinary seaman), 3 oilers, steward, cook, and utility person. The science party outnumbers the crew, and has 22 members: 11 from UTIG (chief scientist, co-chief scientist, 2 OBS people, seismic processor, 6 watchstanders), 3 marine mammal observers, science officer, systems manager, electronics tech, and 5 gunners. We expect to arrive on station to begin deploying OBSs sometime Friday morning or early afternoon. Until then we are passing the time with a safety briefing, a fire and boat drill, daily science meetings, and endless movies to watch.

Gail Christeson
Thur, 10 Jul 2003

We are still transiting to our experiment site at Hess Deep - we now expect to arrive Friday evening. We are spending the time during transit with daily science meetings, preparing the OBSs for deployment, and watching lots of movies (the Ewing has both a VHS and DVD player). Our weather leaving Panama was fantastic, but a day later we had swells and rain, and our speed slowed down. The weather has finally improved, and our speed is back up to about 11 knots. Everyone is anxious to finally start doing some science tomorrow!

Gail Christeson
Sun, 13 Jul 2003

We are finally acquiring data! When we arrived at our experiment region we deployed 16 ocean bottom seismometers (OBSs), and then deployed the seismic streamer and air guns. Everything went smoothly, so we started acquiring seismic data. We soon discovered a 1 knot current, and had to adjust our speed through the water to 4 knots when going from east to west and to 5 knots when going the opposite direction. Everything looked great when I went to bed, but during the night a section of the streamer started sinking and wouldn't recover. So we had to pull the streamer in, expecting to take off some weights. When we got to the suspect section of the streamer we found that the bird (a device that moves the streamer up or down to try to keep it at the ideal depth) was missing - the couplings that attached it to the streamer were sheared right off. We continued pulling in the streamer and found the missing bird dangling by a cord (the bird is attached to the streamer by metal couplings, and then has a cord wrapped around the streamer) - it was caught right next to the next bird. We speculated that the streamer was sinking because the bird got sheared off, but remained dangling from the streamer which was pulling it down. After a short break (which fortuitously coincided with the appearance of chocolate chip cookies hot out of the oven) we started putting the streamer back out. Unfortunately monitoring of the streamer showed that it was still too heavy, so we had to pull some of it back in and start taking weights off (weights are added to the streamer to make it sink to the right depth, but it is an inexact process). We also had to change out 2 sections - one that was low on oil (the oil makes the streamer buoyant), and another that had torn and lost a lot of oil while being put on the reel. But after 8.5 hours we were done and back acquiring data along our 5th profile.

So far we are still determining the best processing to apply to the data we've acquired, but we have detected the layer 2A reflector which is our main target (we are comparing the depth of this reflector with the observed geology to see if it corresponds to the extrusive/dike boundary as many scientists have speculated).

Gail Christeson
Tue, 16 Jul 2003

A good seismic cruise is a boring cruise, and fortunately the past day has been boring. The streamer has been riding at a good depth since we fixed the bird and took off some weights, and there have been no gun problems. We've missed a few shots when one of the computer systems crashes, but otherwise everything is running smoothly and we are on schedule.

To provide a diversion, we constructed a ping-pong table from a sheet of plywood sitting on 2 OBS racks and set it up in the OBS lab (which is now empty since all the OBSs are sitting on the seafloor). No clear dominant player has emerged yet, and Steffen is going to arrange a tournament to be conducted on the transit back to Panama.

We have 3 marine mammal observers on board, but despite observing from sunrise to sunset they have not seen any whales or dolphins that might be affected by our seismic operations (although yesterday a hammerhead shark was sighted). The weather has been windy (often 20 knots) and cloudy, but the seas have been pretty calm.

Gail Christeson
Thu, 17 Jul 2003

Kirk has processed one of the MCS profiles and produced an image of the layer 2A/2B boundary. Since one of the main goals of this project is to see if this boundary correlates in depth to any changes in the geologic stratigraphy, we were all happy to see this image! I've been able to complement the image with a structural model of the depth to the layer 2A/2B boundary along the same profile using a different type of energy (crustal refractions) recorded by the MCS streamer. There is a nice match between my structural model and Kirk's image, which gives us confidence that we'll be able to track the depth to this boundary by both methods.

Our plywood ping-pong table has now been painted green, and a doubles tournament is being organized (random draw). During our transit home we'll have a singles tournament. This provides a good diversion when we are not on watch, although we do seem to lose ping-pong balls with some regularity behind the OBS equipment boxes that are in the same lab.

We are more than halfway through our seismic acquisition, and so far we are right on schedule to accomplish our entire planned program by Sunday evening when we need to start bringing in the streamer and start recovering our OBSs.

Gail Christeson
Sun, 20 Jul 2003

On Friday we had to bring in the streamer one final time as a malfunction caused us to stop recording data. Fortunately the problem was near the front of the streamer, so after about 2 hours we had the streamer back in the water with the problem fixed. The solution was to replace a bad 'can' - a device that converts an analog signal to a digital signal. It is now Sunday evening and we are nearing the end of our seismic survey. At around 10:30 tonight we will finish our last profile, bring in the streamer, and then retrieve our OBSs from the seafloor. We will use 2 methods to release the OBSs. The first method is an acoustic release, where we send a signal from the ship as we near the OBS and the OBS releases from the seafloor. We will use this to get about half the OBSs. The second method is a timed release. All of the OBSs have a timed release programmed into them, and since we know exactly when the OBSs are set to leave the seafloor we can put together a schedule to get the ship to the OBS location at the correct time. It should take us about 31 hours to get all 16 OBSs - about 2 hours per instrument.

We spent the weekend playing a doubles ping-pong tournament. The final match just finished, with Alejandro and Matt defeating Steffen and Mari. Alejandro and Steffen are from UTIG, Matt is the 1st Engineer on the ship, and Mari is a Marine Mammal Observer. We are planning a singles tournament for the transit home, and will have another doubles tournament if there is time (there should be, since it is a 5.5-day transit back to Panama!

Gail Christeson
Mon, 21 Jul 2003

On Sunday evening we finished our last MCS profile. Bringing in the gun array took about 45 minutes, and then we began bringing in the 6 km streamer. This didn't finish until 6:30 a.m.! We are now picking up OBSs, and will continue until tomorrow afternoon. As soon as we get the last OBS on board we'll head back to Panama.

Gail Christeson
Wed, 23 Jul 2003

We've finished up our work at Hess Deep and are now heading back to Panama. Unfortunately 3 of our last 4 OBSs were not recovered, but before that we were 12 for 12. We are now spending our time doing additional processing on the MCS data, and some initial work on the OBS data. So far I've been able to map the seismic layer 2A/2B boundary on 7 profiles located within 4-5 km of the scarp edge. There have been 4 submersible dives in the region mapped by these 7 profiles, and at these locations the seismic layer 2A/2B boundary corresponds well with the observed depth of the extrusive - dike boundary. Since the primary goal of our project was to see if there is a correlation between seismic boundaries and geologic boundaries, it is great to already see that such a correlation does appear to exist!

UT Institute for Geophysics
4412 Spicewood Springs Rd. #600
Austin, TX 78759-8500 USA
Phone: 512-471-6156
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