High-Resolution Seismic Reflection Profiles
Published:January 01, 1983
A.H. Bouma, C.E. Stelting, M.H. Feeley, 1983. "High-Resolution Seismic Reflection Profiles", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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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.
Figures & Tables
Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces
Until a few decades ago, structural and regional geology were traditionally the preserve of field geologists. They usually mapped areas of outcropping deformed rocks and supplemented their work by laboratory studies of rock deformation and by theoretical work. Structural geology became tied to the geology of uplifts, folded belts, and underground mines, all of which were accessible to direct observation. Since World War II we have witnessed a tremendous development of geophysics in oceanography and in petroleum geology. Academic geophysicists in oceanography led their geological colleagues into modern plate tectonics and industry geophysicists developed reflection seismology into a superb structural mapping tool that penetrated the subsurface.
Today we are facing a situation where instruction and textbooks in structural geology are almost entirely dedicated to rock deformation, analytical techniques in detailed field geology and summaries of plate tectonics. Illustrations based on reflection seismic profiles are virtually absent in textbooks of structural geology. These texts illustrate only the parts of the proverbial elephant, together with some conjecture, but without ever offering a glimpse of the whole elephant.
Some of the reason cited for the relative scarcity of published reflection profiles are: 1) the confidentiality of exploration data; 2) difficulties in the photographic reduction and reproduction of seismic profiles for a book format; 3) the two-dimensional nature of vertical reflection profiles; and 4) the obvious distortions in reflection profiles that are typically recorded in time.
The AAPG leadership felt that it was time to attempt to correct the situation and to produce this picture and work atlas. The first volumes, of what may become a series of volumes, are addressing an audience that includes: petroleum geologists concerned with structural interpretations; exploration companies that provide in-house training; the AAPG continuing education program; and academic colleagues interested in updating their curricula in structural geology by inclusion of reflection profiles from the “real world” in their teaching.
The atlas is not meant to be a textbook in reflection seismology (instead we listed some at the end of this introduction) nor a text in structural and/or regional geology. Our intent is simply to provide a teaching tool.