Imaging beneath basalt using an over-under towed-streamer configuration ///

In conventional towed-streamer marine acquisition, shallow sources and cables increase the high-frequency content of the seismic data that is needed for resolution. However, this arrangement attenuates the low frequencies needed for stratigraphic and structural inversion. Towing shallow also makes the data more susceptible to environmental noise. Deep sources and deep cables enhance low frequencies, attenuate high frequencies, and the data has a higher signal-to-ambient-noise ratio due to the more benign towing environment. A conventional towed-streamer survey design, therefore, attempts to balance these conflicting aspects to arrive at a tow depth for sources and cables that optimizes bandwidth and signal-to-noise ratio for a target depth or two-way traveltime, often at the expense of other shallower or deeper objectives. An over/ under, towed-streamer configuration acquires seismic data with cables towed in pairs at two different cable depths, with one cable above the other.

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