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Abstract

Single channel, shallow penetration, high-resolution seismic reflection profiling systems are commonly used by research geologists and by the offshore service industry. The increased resolution produced by high-resolution seismic systems allows for more detailed interpretation of geological phenomena in the upper sedimentary column, which is of paramount importance for platform design and pipeline routes. In many cases, the seismic data are collected as analog records, although industry is increasing its use of digital acquisition systems. Rather than direct analog paper records only, most nondigital users apply analog taping because it permits replaying of rough input data at different filter settings to remove part of the acoustic noise, enhance some of the resolution, and increase penetration. Many groups use more than one acquisition system simultaneously; the different frequencies result in differences in penetration and resolution. The disadvantages of using a multisensor seismic system are acceptable and normally only result in cross talk between the systems.

Most of the common high-resolution reflection systems fit into the following categories (Sieck and Self, 1977; Sylwester, 1982): 1) tuned transducer-frequency range 3.5 to 7.0 kHz, subbottom penetration to 30 m (100 ft); 2) electromechanical-frequency range 0.8 to 5.0 kHz, subbottom penetration to 120 m (390 ft); 3) sparker-frequency range 0.04 to 0.150 kHz, subbottom penetration to 1000 m (3,300 ft); and 4) airgun-frequency range 0.02 to 0.50 kHz, subbottom penetration to 3000 m (10,000 ft). Heavier sparkers and larger airguns are used for medium and deeper penetration (3 to 5 seconds two-way traveltime).

In this chapter, we present examples with our interpretation of geological phenomena of Upper Pleistocene and Holocene deposits from the Gulf of Mexico continental margin off Texas and Louisiana and from the Mississippi Fan collected with 3.5 kHz, minisparker, and small airgun systems (Figure 1, Table 1). To demonstrate the differences in penetration and resolution, each geologic phenomenon is presented as it is recorded by the individual systems.

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