We’re approaching the end of our expedition. We have only a few hours left of transit back to Kodiak Island… Despite a late departure and a day of bad weather in the last part of the cruise, this cruise was a success! In total, we triggered the source 7824 times along 3146 km (1955 miles) of profiles, going back and forth along the Alaska Peninsula subduction zone, in an area that is known to have produced some huge earthquakes and devastating tsunami in the past century. The acoustic waves we generated were recorded on a 4-km long streamer data towed behind the ship. This gives us access to images of the subseafloor to depths of tens of kilometers in quasi-real time.. well, we actually have to do some processing before getting the CAT-scan type images… Hopefully, the acoustic waves have also been recorded on part or all 75 seismometers that have been deployed a year ago and are now standing on the seafloor and the 30 seismometers that have been installed on-land if the bears have not found and damaged them… Can’t wait to see our shots on the seismometer data! But I’ll have to be patient, the seismometers are going to be picked up in August and September this year.. Both types of data will help us to understand how subduction zone work. Although we’ve learned a lot about how they work over the years, there are still some mysteries that requires more data to be acquired and analyzed.
As you’ve seen from the previous blog entry photo, the acquisition of marine seismic data is not an easy task and required a lot of hard work onboard as well as planning beforehand so I’m using this blog to thank the R/V Marcus G. Langseth technical staff and crew, the Captain, the 6 protected species observers and people of the Office of Marine Operations at Lamont for their very hard work. They truly did an excellent job before and during this expedition and it’s been a real pleasure to work with all of them.
One of the most rewarding part of this cruise, besides collecting and processing new exiting data is the training component of this cruise. We brought 8 students and one early career scientist onboard with us, with very different backgrounds and from 8 different institutions. For the majority of them, it was their first experience on a research vessel and they knew very little about subduction zones and seismic data acquisition and processing before this cruise. Yesterday afternoon, each of them gave a 10-min presentation on the processing and interpretation of the new multichannel seismic data we collected during our cruise and I was very impressed (and touched) by how well they did. These gave very excellent presentations! They all pointed out key features they saw on the new data and together they made a summary of major trends they observe in terms of roughness of subducting oceanic plate, amount of sediments subducted, structure in the overriding plate and deeper reflections. None of them worked together before this cruise, and seeing them having scientific interactions in preparing these presentations as well as the new friendship forming over the course of these two weeks was extremely heartwarming and this 17-day cruise has definitely strengthened the ties between young geoscientists from all over the US. They are a wonderful group of motivated and hard-working students and early career scientists!
Emma Myers helped A LOT with the training component, she dedicated so much of her time showing the students how the software we were using was working, explaining the different processing steps to be applied to the data and answering many questions. Thanks a lot Emma! Dave Foster from the USGS shared his expertise in multibeam seafloor mapping and sub-bottom echo-sounding. It was exciting to watch a detailed map of the seafloor in the region evolve over the course of the cruise, thanks to Dave’s hard work.
I will finish this post by thanking Anne Sheehan, who has been an awesome co-chief scientist, enthusiastic, chill and fun (what else should I have hoped for?) and the National Science Foundation GeoPRISMS and Marine Geology and Geophysics programs for funding this experiment and supporting this vessel.
Anne Bécel, Lamont Doherty Earth Observatory/Columbia University
Langseth science technical staff having a little break during transit. From left to right Brian Agee, Tom Spoto, Dave Martinson (behind, Chief Science Officer), Alan Thompson and Chris Abdouch. (Photo credit: Anne Bécel)
Gökçe Astekin showing her interpretation of the new seismic data we collected during this survey. (Photo Credit: Anne Bécel)
Dave Foster and Carlos Gomez view new seafloor bathymetry data that we have collected on this cruise. (Photo Credit: Anne Sheehan)
Captain Dave Wolford and co-chief scientist Anne Sheehan confer during ocean passive acoustic monitoring test. (Photo Credit: Anne Bécel)
Seismic source being brought back on board the R/V Marcus Langseth at the completion of our project data collection. Sunset over Veniaminof volcano in the background. (Photo Credit: Anne Sheehan)