Two-dimensional information of fissure traces is gathered from outcrops through digital imaging to study the occurrence of fracture surfaces within rocks and simulate the spatial distribution of fissure networks inside rocks.These studies are of great significance to the prediction of subsurface resources (especially fluid resources) and the evaluation of stability subsurface space.Fissures within rocks can be divided into several groups according to their clustering patterns.It is assumed that the fissures in each group spread around a central value.The relations between occurrences of fissure surface and wall surface and dip of fissure trace are defined with the included angle between lens direction and normal line of the wall and are used to estimate the occurrence of a given fissure surface.Random function is used to define fissure distribution based on the Fisher distribution.Dips of fissure traces are used to delineate the three-dimensional distribution of fissure surfaces.The final step is to develop a consistent method for solving the inverse problem and controls the calculation error under 5% by using simulated annealing method.The method had been applied to the investigation of fissures on outcrop in Gaosong ore field in GeJiu tin deposit.The fissures were divided into two sets with average dips of 49.0° (SD of 0.38) and 128.2° (SD of 0.32) respectively and their occurrences were estimated.The first set has a mean dip direction of 171.1°and a mean dip angle of 75.1° and the second has a mean dip direction of 338.3° and a mean dip angle of 3.9°They fit well with field data.Simulation of fissure network was carried out based on the concept and yielded very positive results.Overall

the method shows great potential for direct estimation of 3D distribution of fissures according to fissure trace direction on outcrop.