A.W. Bally, 1983. "Strike Slip Tectonics - Introduction", 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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Tectonics associated with strike-slip (wrench) fault zones, or perhaps better oblique-slip zones, have in recent years received considerable attention. It may be desirable to clarify the nomenclature of such fault zones, but any attempt to do this will probably sooner or later stumble because a reasonably complete three-dimensional documentation based on reflection seismic data does not yet exist. For our purposes, strike-slip systems, oblique-slip systems, and wrench fault systems are considered to be roughly synonymous.
We find the definition of K.B. Sporli (as quoted by P. E Ballance and H.G. Reading) for obliqueslip mobile zones particularly instructive:
"Across an oblique-slip mobile zone the relative motion of the blocks which are in contact along the zone is oblique, that is, in plain view there are components of movement both parallel and perpendicular to the zone. The zone may be a plate boundary, in the form of an active continental margin, an island arc, a collision zone between various plate features (e.g. continent/continent, arc/ridge), or an oceanic or continental transform. One may also wish to include rift zones with oblique directions of spreading, at least during their initial stages of opening, especially in the case of narrow back-arc basins and of continental aulacogens. Oblique-slip mobile zones may lie within a non-rigid plate. The width of the mobile zone is usually measured in tens of hundreds of kilometers.
In oblique-slip mobile zones, transpression and/or transtension may occur. If subduction is taking place, the third dimension in the form of a vertical component or movement will also be important, and the definition of oblique-slip then becomes identical with that for oblique-slip faults (Spencer; 1977); i.e. oblique-slip subduction has both strike-slip and dip-slip components of movement. Vertical movement is also important at a smaller scale and as a second order component in the oblique-slip mobile zones without subduction."
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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.