TSK 11 Göttingen 2006 Deckert & Gessner Application of Photogramme- try in Geology: 3D Investiga- tion of Rock Fracture Distri- butions Poster Hagen Deckert1 Klaus Gessner2 Geology as a science has an important visual component and the knowledge of any geologist is deeply linked to visual experience of rock outcrops, thin sec- tions and analytical images. One of the shortcomings of most geological images such as maps, cross sections and out- crop photographs is that they are 2D, while processes geologists are interested in are typically occurring in 3D space. The 3D geometry of faults, fractures and joints is crucial to quantify geologi- cal processes related to fracture mechan- ics, such as hydrothermal mineralization and ground water flow, but also geotech- nical problems such as rock mass stabil- ity. A number of studies have shown that some geological structures can be described with a scale invariant, fractal distribution. So far these observations on which these findings are based were restricted to one and two dimensions and has been difficult to obtain a full spatial geometric picture of fracture sets from rock outcrops, because much of the rock is not directly accessible. However, without taking into account the spatial distribution of geological structures the true geometry of joint patterns cannot be fully described and scaling laws, frac- tal or not, cannot be derived. We present images of joint patterns based on datasets acquired by digi- 1 Institut für Geowissenschaften, Johannes Gutenberg-Universität, Becherweg 21, 55099 Mainz, Germany 2 School of Earth and Geo- graphical Sciences, University of Western Aus- tralia, 35 Stirling Highway, Crawley WA 6008, Australia tal photographs which are processed to three dimensional images using the photogrammetry software Siro3D. This technique allows to obtain a highly ac- curate 3D picture of the visible out- crop. The spatial pattern of joints in nature is investigated using the soft- ware SiroJoint. For the analysis of joint systems a large data set was collected from the Heavitree Quarzite at Ormis- ton Gorge, near Alice Springs. The Heavitree Quartzite is fragmented by a spectacularly regular three-dimensional joint pattern, which is repeated at dif- ferent scales and therefore represents a perfect laboratory for our investigations (Hobbs 1993). Siro3D generates a spa- tially fully referenced 3D image from overlapping digital images, such that each pixel of the image is assigned spa- tial coordinates. The software SiroJoint routinely constructs planes from the in- tersection of the rock-face with the lin- ear trace of planar features (Poropat 2001). It provides stereographic plots of structural elements and additionally measures joint persistence, area, and joint spacing. Our measurements allow to analyse geometrical scaling relation- ships of joint sets with high accuracy and will help explore the character of their 3D complexity. Several hundred joint planes were de- fined with SiroJoint in an Ormiston Gorge outcrop. Three different joint sets can be distinguished. Joint set one and two are characterized by steeply in- clined planes with joint spacings rang- ing between 2 cm to 40 cm and 2 cm to 10m respectively. Both joints sets de- pict a power law distribution in joint spacing/frequency plots. The third set is defined by a subhorizontal orienta- tion. It shows a very regular spacing in the meter scale and lacks an exponen- 1 Deckert & Gessner TSK 11 Göttingen 2006 tial distribution. We intend to use the results as a basis to compare observed fracture pattern with those generated by computational methods like Iterated Function Systems. This might help to understand how physical rock proper- ties influence the spatial complexity of fracture systems and develop constitu- tive scaling relationships for certain rock types. References Hobbs BE (1993) The Significance Of Struc- tural Geology In Rock Mechanics, Chapter 2, in: Comprehensive Rock Engineering 1, Hoek E, Hudson J & Brown ET (eds.), Perg- amon Press, 25–62. Poropat GV (2001) New methods for map- ping the structure of rock masses, Australian Institute of Mining and Metalurgy, Confer- ence Proceedings EXPLO2001. Huntersval- ley, NSW, Australia. 2