Automated modelling of folds from structural data

@inproceedings{RUNKJRM40,
 abstract = { Folds present a challenge for 3D modelling because the geometry of the fold is not explicitly
contained in individual observations of the folded surface. The interpolation algorithms at the
base of structural modelling fit surfaces with minimal curvature to structural observations. Folds
typically produce patterns of localised variation in curvature. To obtain folded geometries the
geologist is required to draw fold shapes or add interpretive constraints to control the fold geometry.
This is a subjective process and means that the models are generally not reproducible. A new
method for modelling folds uses a fold frame with coordinates based on the structural geology of
folds: fold axis direction, fold axial surface and stretching lineation. The fold geometry can be
characterised by rotating the fold axis direction field and fold axial surface field to give the final
orientation of the folded surface. These rotations angles can be expressed as 1D functions of the
fold frame coordinates. In this contribution we present methods for extracting and automatically
modelling the fold geometries from structural data. The fold rotation angles used for characterising
the fold geometry can be calculated locally from structural observations. The fold rotation angles
incorporate the structural geology of the fold and allow for individual structural measurements
to be viewed in the context of the folded structure. To filter out the effects of later folding the
fold rotation angles are plotted against the coordinates of the fold frame. Using these plots the
geometry of the folds can be interpolated directly from structural data where we use a combination
of radial basis function and harmonic analysis to interpolate and extrapolate the fold geometry.
This technique is applied to two natural case studies, an outcrop of an asymmetrical fold within
the Lachlan Fold belt at Cape Conran, Victoria, Australia and a fold interference pattern from the
Pilbara, Western Australia. },
 author = { Grose, Lachlan AND Ailleres, Laurent AND Laurent, Gautier },
 booktitle = { 2016 RING Meeting },
 publisher = { ASGA },
 title = { Automated modelling of folds from structural data },
 year = { 2016 }
}