It is increasingly apparent that faults are typically not discrete planes but zones of deformed rock with a complex internal structure and three-dimensional geometry. In the last decade this has led to renewed interest in the consequences of this complexity for modelling the impact of fault zones on fluid flow and mechanical behaviour of the Earth’s crust. A number of processes operate during the development of fault zones, both internally and in the surrounding host rock, which may encourage or inhibit continuing fault zone growth. The complexity of the evolution of a faulted system requires changes in the rheological properties of both the fault zone and the surrounding host rock volume, both of which impact on how the fault zone evolves with increasing displacement.

Physicists attempt to reduce natural phenomena to their essential dimensions by means of simplification and approximation and to account for them by defining natural laws. Paradoxically, whilst there is a critical need in geology to reduce the overwhelming field information to its essentials, it often re- mains in an over-descriptive state. This prudent attitude of geologists is dictated by the nature of the subjects being considered, as it is often difficult to derive the significant parameters from the raw data.

Often times a student is introduced to geophysics as a rather specialized branch of geology, employed only for prospecting or in graduate research. Geophysics courses are usually taken later in a college schedule after adequate preparation in physics and mathematics. Because it is a broad, interdisciplinary area of physical science, one can obtain a background in geophysics by taking selected studies in several different but related fields.

Many of the problems which arise during a study in structural geology are essentially exercises in three-dimensional geometry. Data acquired from field-observations—strike and dip of planes (beddingplanes, planes of schistosity or cleavage, faults, etc.), the pitch and plunge of lineations (outcrops, slickensides, micro-folds, flow-lines, elongation of mineral components or of inclusions, etc.) and all other related vector data are incorporated in a geological map and in accompanying illustrative sections. Both in the construction of such sections and of related block-diagrams, and in the further study of the structural features of an area, it is frequently necessary to make various calculations. Sometimes, indeed, as in many of the problems of mining geology and in the interpretation of borehole cores, the necessity for calculation arises at an even earlier stage since such fundamentals as the dip and strike of a bedded series are only indirectly derived from the observed data.  <...>

The area to he described consists of two irregularly elongate outcrops of Lower Carboniferous sedimentary rocks in the counties of Tyrone, Fermanagh, and Donegal; the larger southern outcrop, covering 148 square miles, extends from Lough Erne in the west to the Strule Valley in the east; the northern outcrop, about 30 square miles in extent, lies about six miles north of the southern outcrop.

In the application of potential fields in regional investigations, the gravimetric method solves the problems of the study of regional geological constitution, with better results for the folded belts. Regional studies that make use of gravimetric surveys also permit detailing the main tectonic features such as faults and other alignments, with which various mineral and energy resources are linked.

In geologic terms, a plate is a large, rigid slab of solid rock. The word tectonics comes  from the Greek root "to build." Putting these two words together, we get the term plate tectonics, which refers to how the Earth's surface is built of plates. 
The theory of plate tectonics states that the Earth's outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another as they ride atop hotter, more mobile material. The diagrams below show the break-up of the supercontinent Pangaea (meaning "all lands" in Greek), which figured prominently in the theory of continental drift -- the forerunner to the theory of plate tectonics. <...>

The material in this book is derived from an intensive course in X-ray structure analysis organized on behalf of the Chemical Crystallography Group of the British Crystallographic Association and held every two years since 1987. As with a crystal structure derived from X-ray diffraction data, the course contents have been gradually refined over the years and they reached a stage in 1999 (the seventh course) where we considered they could be published, and hence made available to a  far wider audience than can be accommodated on the course itself.

Even though our limited perceptions provide us with only a brief glimpse of the Universe, the main lesson that we learn from our observation is that the world is complicated. Very complicated. Every part of the universe interacts with the other parts; the responses of each component are never proportional to the applied forces, and the feedbacks of one subsystem on another cannot be discarded. As a result, processes are unpredictable, and chaotic behavior is a common occurrence. Disorder and turbulence become rife. Yet from the chaotic background, coherent structures sometimes emerge, patterns form, and local order is generated.

Let us start with a question here. Which figure in Fig. 1.1 is the most symmetric? Obviously, figure (c) in Fig. 1.1 has less symmetry than (a) and (b); however, it is difficult to compare symmetries of (a) and (b).
One of the basic tools for describing symmetries of crystal structures is space groups, which describe symmetry of atoms (vertices/points) in a crystal structure. For example, the symmetry of a regular hexagonal tiling of R2 is described by the group P6m, and the space group of the symmetry of a regular three-colored hexagonal tiling (see Fig. 1.2b) is P3m1. Similarly, the group P6m describes the symmetry of a regular hexagonal lattice.