- Copyright © 2008 Society of Exploration Geophysicists
A pressure sensor in a towed streamer always records two wavefields that interfere with each other. The two wavefields are the upgoing pressure wavefield propagating directly to the pressure sensor from the Earth below, and the downgoing pressure wavefield reflected downwards from the free (sea) surface immediately above the streamer. Thus, every reflection wavelet recorded by conventional marine streamers is accompanied by a “ghost” reflection from the ocean's surface. The reflection wavelet is undesirably elongated, reducing temporal resolution. The consequence, as illustrated on the left of Figure 1, is that a series of receiver ghost notches is introduced into the frequency spectra. There has historically been a forced trade-off between towing shallow to record high-frequency (but noisy) data at the cost of reduced lower frequencies, or towing deep to record low frequencies at the cost of reduced higher frequencies.