It’s been a week since we deployed all of our gear and started steaming along our lines, so now we have amassed a lot of data! Although we can only steam at very low speeds while towing the equipment (~4.5 nautical miles an hour or ~5 mph), each time we fire the air gun array, the 636 channels on the seismic streamer listen for returning sound waves for 18 seconds and record a total ~25 Mb of data. Repeat that every 30 seconds for 7 days, and it begins to add up! We now have 400 Gb of seismic data alone, not including all of the other types of data we collect while underway (bathymetry, magnetics, gravity). We are a data-collecting machine.
Not only are we collecting data, we are also doing some preliminary data analysis to get a first look at the geology hidden below the ocean, which is always exciting.
|Kara and Matt are entranced by velocity analysis|
Although we are only a week in, our data collection has already taken us through water depths as shallow as 20 m and as deep as 6000 m. At the edge of the continental shelf, water depths change rapidly from ~500 to ~3000 m over just 20 km – a slope of 10%. For perspective, that’s very similar in elevation change and slope to the course for the Pikes Peak marathon.
|Perspective view of seafloor depth from MGDS across the continental slope overlain by a higher resolution swath of bathymetric data that we acquired along our transect, which is also shown projected onto the seafloor.|
We have also traveled over widely variable geology – from 35-km-thick continental crust to ~7-km-thick oceanic crust, and from sediment thicknesses of 5 m to over 7 km. Our data are also revealing cool structures in the sediments and crust – faults, sediment waves, and more. Below is a picture of a salt diapir that we imaged at the edge of the continental margin. The salt was probably first deposited at least 150 millions years ago in a flat layer, but as more sediments were deposited on top of it, it got squeezed up and out into dramatic diapirs.