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Analogue and Numerical Sandbox Models |
1 Institute of Geological Sciences, University of Bern, Baltzerstrasse 1-3, CH-3012 Bern, Switzerland schreurs{at}geo.unibe.ch
2 Centre for Geodynamics, Geological Survey of Norway, 7491 Trondheim, Norway
3 Department of Geology, University of Toronto, 22 Russell St., Toronto, Ontario M5S 3B1, Canada
4 CNR-Istituto di Geoscienze e Georisorse, Sezione di Firenze, via G. La Pira 4, I-50121 Firenze, Italy
5 Dipartimento di Scienze della Terra, Università di Parma, Parco Area delle Scienze 157/A, I-43100 Parma, Italy
6 Institut Français du Pétrole, 1 et 4 avenue de Bois Préau, F-92500 Rueil Malmaison, France
7 GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany
8 Hans Ramberg Tectonic Laboratory, Department of Earth Sciences, Uppsala University, Villavägen 16, S-75326 Uppsala, Sweden
9 Dipartimento di Scienze della Terra, Università di Pavia, via Ferrata 1, I-27100 Pavia, Italy
10 Department of Geological Sciences, Rutgers University, Piscataway, NJ, 08854, USA
11 Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto 606-5801 Japan
12 Dipartimento di Scienze della Terra, Università di Firenze, via G. LaPira 4, 1, I-50121 Firenze, Italy
* Midland Valley Exploration Ltd., 14 Park Circus, Glasgow, G3 6AX, UK
We report a direct comparison of scaled analogue experiments to test the reproducibility of model results among ten different experimental modelling laboratories. We present results for two experiments: a brittle thrust wedge experiment and a brittleviscous extension experiment. The experimental set-up, the model construction technique, the viscous material and the base and wall properties were prescribed. However, each laboratory used its own frictional analogue material and experimental apparatus. Comparison of results for the shortening experiment highlights large differences in model evolution that may have resulted from (1) differences in boundary conditions (indenter or basal-pull models), (2) differences in model widths, (3) location of observation (for example, sidewall versus centre of model), (4) material properties, (5) base and sidewall frictional properties, and (6) differences in set-up technique of individual experimenters. Six laboratories carried out the shortening experiment with a mobile wall. The overall evolution of their models is broadly similar, with the development of a thrust wedge characterized by forward thrust propagation and by back thrusting. However, significant variations are observed in spacing between thrusts, their dip angles, number of forward thrusts and back thrusts, and surface slopes. The structural evolution of the brittle-viscious extension experiments is similar to a high degree. Faulting initiates in the brittle layers above the viscous layer in close vicinity to the basal velocity discontinuity. Measurements of fault dip angles and fault spacing vary among laboratories. Comparison of experimental results indicates an encouraging overall agreement in model evolution, but also highlights important variations in the geometry and evolution of the resulting structures that may be induced by differences in modelling materials, model dimensions, experimental set-ups and observation location.
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  S. J. H. Buiter, A. Yu. Babeyko, S. Ellis, T. V. Gerya, B. J. P. Kaus, A. Kellner, G. Schreurs, and Y. Yamada The numerical sandbox: comparison of model results for a shortening and an extension experiment Geological Society, London, Special Publications, 2006; 253: 29 - 64. [Abstract] [PDF]
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