ANALOG MODELING - FROM A QUALITATIVE TO A QUANTITATIVE TECHNIQUE - A HISTORICAL OUTLINE

Analogue modelling is a simplification of Nature; using this method, s tructures formed due to the deformation of rocks, whose in situ proper ties may be poorly known, can be modelled and investigated. Our back o f knowledge about ''real'' rocks is one of the major limitations to an y kind of modelling of deformation. However, unlike their counterparts in Nature, the initial (undeformed) stages of analogue models can be documented, and can easily be compared with their later deformed stage s. This comparison is essential to gain an understanding of the evolut ion of the resulting structures. Analogue modelling is a relatively si mple and inexpensive technique which can be very valuable as long as i ts limitations are well understood. In rock mechanics, real rocks are strained over human time scales. As many of the properties of rocks ar e time-dependent, the results of this type of experiment cannot direct ly be extrapolated to geologic time scales. Instead, modellers diminis h the temporal and spatial dimensions by substituting carefully-chosen analogue materials for real rocks. Unlike field geologists, analogue modellers are able to follow the development of their models in a fixe d reference frame. Cloos (1955) noted that: ''Many interpretations wou ld never have been published if the author had only once tried his sug gested mechanism of folding or faulting in an experiment....''; he als o concluded that ''[analogue] experimenting is a good deal of fun ''!