8-km Streamer Data

During MGL0804 we achieved a UNOLS first by deploying an 8-km, 636-channel streamer. (Technically the streamer length was 7950 m, but we're calling it 8 km.) This was achieved by joining the first 2 km of streamer #1 to the entire 6-km length of streamer #2 (the Langseth carries four 6-km streamers for 3D work). The streamer flew very nicely at 6 m depth throughout the cruise (aided, no doubt, by the good weather we enjoyed):

Having source-receiver offsets this large will enable a host of new scientific possibilities. The figures below show two examples of shot gathers that demonstrate the new capability. In both figures, the vertical axis is two-way traveltime in second, and the horizontal axis is "channel number", with channel 636 being closest to the ship and channel 1 furthest, at more than 8 km source-receiver offset.

This first example shows a bright wide-angle reflection coming in at about 6 seconds near the left edge. This reflection would barely be visible on a mere 6-km streamer, and the bright amplitudes showing the "critical distance" (which is important for amplitude modeling) would have gone unobserved.

The second example shows a gather in shallower water. The outer (left) half of the gather shows refractions from sedimentary layers (which provide very precise velocities) as well as a wide-angle reflection that intersects the left edge of the figure at 5 seconds. Again, with a shorter streamer, most of this information would have been missed.

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