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Professors Aydin and Pollard have contributed several articles and chapters in edited books reviewing historical and current
topics in structural geology and tectonics.
Pollard and Segall (1987) review the quasi-static solutions for
two dimensional cracks in a linear elastic whole-space subject to uniform stress (traction) boundary conditions. Complete displacement and stress field
equations are given for mode I, II, and III. Applications are described for the 1906 San Francisco earthquake event; the
deformation associated with veins and solution surfaces at the tip lines of small faults; spacing of joints in layerd rock; the
dilational form of igneous dikes; and joints in the process zone of a dike.
Pollard and Aydin (1988) review progress in understanding
jointing over the century (1888-1988) as part of the Geological Society of America's Centennial Year special issue of the
Bulletin. This contains both an historical review of what was published (with critical commentary), and an outline of what can
be synthesized from these published papers. The fundamental relationships from continuum and fracture mechanics that are
relevant to the initiation, propagation, and termination of joints are reviewed. It is argued that these relationships combined
with appropriate field observations provide the best prescription for future progress.
Aydin (1996) is the second chapter in the National
Research Council Committee book on Rock Fractures and Fluid Flow: Contemporary Understanding and Application
s published by the National Academy Press. In this chapter the physical characteristics of fractures and fracture patterns are
reviewed. A geological and geomechanical understanding of fracture formation is described, and the characteristics of various
fracture types, network patterns and the internal structure of fractures are documented and discussed.
Aydin (2000) reviews the
practical aspects of fractures and faults in reservoirs, and discusses the nature of hydrocarbon entrapment, migration and flow as
influenced by these structures. This is meant to address the large issue of the roles of structural heterogeneities in the
migration and entrapment of hydrocarbons. The permeability of joints, deformation bands, and faults is described and it is
argued that these structures should be included in large-scale basin models and reservoir-scale simulation models. This
proposition is supported by case studies.
Recently, Professor Pollard has been an active proponent for the use of a complete mechanical
analysis in the investigation of problems in structural geology and tectonics. A paper presented in the 20th Anniversary Issue
of the Journal of Structural Geology (Fletcher and Pollard,
1999) addresses the question: "Can we understand structural and tectonic processes and their products with appeal to a
complete mechanics?" In the abstract the authors begin: Our answer
is 'no', and then they go on to defend this position using two examples, one addressing the development of chevron folds and
the other the development of echelon veins. They conclude that further progress in understanding these (and other) products of
structural and tectonic processes can be made through an integrative approach using a complete and self-consistent
mechanics.
Pollard (2000) is a Discussion of one of the
papers in the 20th Anniversary issue of the Journal of Structural Geology authored by Marrett and Peacock (1999). This
discussion addresses the historical development of structural analysis and the conceptual role of stress and strain in the
analysis of structures. Some of the opinions in the original paper are challenged and a position is taken that advocates a
research methodology that integrates geometry, kinematics, and dynamics. It is argued that geometric observations do not
constitute the foundation of all structural analysis, but rather that this foundation is constructed from the conservation laws of physics, so geometric
observations are properly viewed as data, some of which may be useful for testing refutable hypotheses.
Partly in response to Fletcher and Pollard (1999) and to
other articles in the 20th Anniversary volume that took a decidedly different stance Bill Dunne and Jim Evans organized a debate at the 2000 GSA Meeting in Reno with the topic: "Kinematics
vs. Mechanics in Understanding Rock Deformation" sponsored by the GSA Structural Geology and Tectonics Division. As a part
of that debate a play was presented called "A Complete Suite",
a musical allegory of mechanics in one act.
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