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Geological Survey of FinlandEevaliisa Laine and Mira Markovaara-KoivistoGeological Survey of Finland (GTK), P.O. Box 96, 02151 Espoo, FINLAND (email: firstname.lastname@gtk.fi)

Introduction

Rock fracturing affects directly to rock properties, for example, dissemination of metals and pollutants in the groundwater, thermal conductivity through water flow and rock stability. The purpose of the present study was to combine statistical analysis of fracture properties and 3D visualization tools in analyzing fracturing of Precambrian bedrock in southern Finland and, finally, to build a workflow for fracture network modelling. The study sites included Palmottu and Kopparnäs areas. The fractures and faults could be interpreted from the detail elevation models. The interpreted faults and fractures from elevation models and geophysical maps were combined and validated using direct geo-logical observations from outcrops and drill core logs. Spatiostatistical analysis of these combined fracture data were used in building 3D fracture network. So, the final work-flow for fracture network modeling include spatiostatistical analysis and 3D visualization of interpreted fractures and faults.

The 3D visualization and analysis of fracturing by using Laser scanning data, geological maps and geophysical data - study sites from southern Finland

Work flow for fracture network modelling

Kopparnäs case study

Figure 1. Superficial deposits draped on the Laser scanning elevation model. Red – thin overbur-den or outcrop, green – sand, dark blue – clay, light blue – water. DTM made from drone images with the high-resolution images draped onto the model. Fractures were mapped with scanline technique and plotted with Structural Suite by Surpac. Red colour of the surfaces indicate rough fracture surfaces, yellow slightly rough and green smooth.

1. Location of the study sites relative to the main structural features based on the Digital Map database (Geological Survey of Finland) and regional geophysical data such as Bouguer anom-aly maps. Palmottu and Kopparnäs study sites are located within the major parallel structures bordering the LPM granulites in southern Finland.

2. The use of semiregional geophysical maps to analyse structural features surrounding the study sites. In the case of Palmottu and Kopparnäs study sites the magnetic anomalies show the general trend of the lithological units and possible discontinuities striking to northwestern direc-tion (dashed lines).

3. Elevation models built from Laser scanning data (National Land Survey in Finland) can be used to analyse the local structures. In the Palmottu study site two major structures are striking to Northeast and to the North (solid arrows). In addition, few possible fracture surfaces were in-terepeted from the elevation map (dashed arrows).

4. Drone photographs were used together with scanline measurements to collect fracture data. GOCAD FractCar plugin.

5. Drill core data and bedrock observations will be combined to build the final fracture network models for Palmottu and Kopparnäs study sites in southern Finland. The fracture network model is based on the drill core data from the Palmottu study site visualized by stereographic projec-tions with Paradigm GOCAD and fracture simulation was done using GOCAD FractCar plugin.

Acknowledgements

The present study is a part of the Finnish Research Programme on Nuclear Waste Man-agement (KYT) 2015-2018 and, more spefically, the project, ROSA: Fracture simulator which respects the measured fracture length and orientation distributions.

References

Ahonen, L., Kaija, J., Paananen, M., Ruskeeniemi, T. and Hakkarainen, T. (2004). Palmottu natural analogue: A summary of the studies. Geological Survey of Finland, Report YST-121, 39 pages, 1 appendix. ISBN 951-690-896-9, ISSN 0783- 3555.Kuivamäki, A., Paananen, M., and Kurimo, M. (1990). Structurai modelling of bedrock around he Palmottu U-deposit, progress report 1990. Geological Survey of Finland, Nuclear Waste Dis-posal Research, Report YST-72, 29 pages, 27 figures, 2 tables and 32 appendices.Paulamäki, Seppo, Lindberg, Antero, Paananen, Markku and Blomqvist, Runar, 1997. The Palmottu Analogue Project, Technical Report 97-17.Villar, L.P., Campos, R., Cozar, J.S., Pardillo, J., Pelayo, M. and Labajos, M.A. (1997). Structur-al, lithological and mineralogical analyses of borehole R-385 (386) from the Palmottu site (Fin-land). The Palmottu Analogue Project, Technical Report 97-05.

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