Recent interest in the influence of rock fractures on fluid movement through rock has created a need for modeling techniques which can predict fracture geometry, spacing, and opening in large, heterogeneous rock bodies. A suggested approach involves the simultaneous development of (1) a rock body model which represents the distribution of rock physical properties and the boundaries between property domains; (2) an empirical model representing fracture geometry, distribution, and opening for as much of the rock body as is feasible; and (3) a theoretical strain model which allows the strains indicated by the empirical model to be generalized over the body model. The theoretical model is based on the analysis of strain mechanisms during field work for the empirical model. Th s methodology has been applied to a complex nearshore sedimentary rock sequence in an area having widely spaced basement-rooted faults of the Laramide type. The resulting model was sufficiently powerful to predict acceptably fracture aperture size and spacing in the strata of interest. These predictions

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provide input for the existing geohydrologic models for fracture flow which is significantly less variable than permitted by the models' sensitivity to this parameter.

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