Open-source, implicit 3D structural geological modeling in Python for uncertainty analysis.

GemPy is a Python-based, open-source library for implicitly generating 3D structural geological models. It is capable of constructing complex 3D geological models of folded structures, fault networks and unconformities. It was designed from the ground up to support easy embedding in probabilistic frameworks for the uncertainty analysis of subsurface structures.

Check out the documentaion either in github pages (better option), or read the docs.

• Features
• Getting Started
  • Dependecies
  • Installation
• Documentation
• References

The core algorithm of GemPy is based on a universal cokriging interpolation method devised by Lajaunie et al. (1997) and extended by Calcagno et al. (2008). Its implicit nature allows the user to automatically generate complex 3D structural geological models through the interpolation of input data:

• Surface contact points: 3D coordinates of points marking the boundaries between different features (e.g. layer interfaces, fault planes, unconformities).
• Orientation measurements: Orientation of the poles perpendicular to the dipping of surfaces at any point in the 3D space.

GemPy also allows for the definition of topological elements such as combining multiple stratigraphic sequences and complex fault networks to be considered in the modeling process.

GemPy itself offers direct visualization of 2D model sections via matplotlib and in full, interactive 3D using the Visualization Toolkit (VTK). The VTK support also allow to the real time maniulation of the 3-D model, allowing for the exact modification of data. Models can also easily be exportes in VTK file format for further visualization and processing in other software such as ParaView.

GemPy was designed from the beginning to support stochastic geological modeling for uncertainty analysis (e.g. Monte Carlo simulations, Bayesian inference). This was achieved by writing GemPy's core architecture using the numerical computation library Theano to couple it with the probabilistic programming framework PyMC3. This enables the use of advanced sampling methods (e.g. Hamiltonian Monte Carlo) and is of particular relevance when considering uncertainties in the model input data and making use of additional secondary information in a Bayesian inference framework.

We can, for example, include uncertainties with respect to the z-position of layer boundaries in the model space. Simple Monte Carlo simulation via PyMC will then result in different model realizations:

Theano allows the automated computation of gradients opening the door to the use of advanced gradient-based sampling methods coupling GeMpy and PyMC3 for advanced stochastic modeling. Also, the use of Theano allows making use of GPUs through cuda (see the Theano documentation for more information.

For a more detailed elaboration of the theory behind GemPy, take a look at the upcoming scientific publication "GemPy 1.0: open-source stochastic geological modeling and inversion" by de la Varga et al. (2018).

GemPy requires Python 3 and makes use of numerous open-source libraries:

• pandas
• tqdm
• scikit_image
• Theano
• matplotlib
• numpy
• pytest
• scipy
• ipython
• seaborn
• setuptools
• scikit_learn
• networkx

Optional:

• vtk>=7 for interactive 3-D visualization
• pymc or pymc3
• steno3d

Overall we recommend the use of a dedicated Python distribution, such as Anaconda, for hassle-free package installation. We are curently working on providing GemPy also via Anaconda Cloud, for easier installation of its dependencies.

We provide the latest release version of GemPy via the Conda and PyPi package services. We highly recommend using either Conda or PyPi as both will take care of automatically installing all dependencies.

$ pip install gempy

Otherwise you can clone the current repository by downloading is manually or by using Git by calling

$ git clone https://github.com/cgre-aachen/gempy.git

and then manually install it using the provided Python install file by calling

$ python gempy/setup.py install

in the cloned or downloaded repository folder. Make sure you have installed all necessary dependencies listed above before using GemPy.

Extensive documentation for GemPy is hosted at gempy.readthedocs.io, explaining its capabilities, the theory behind it and providing detailed tutorials on how to use it.

• Calcagno, P., Chilès, J. P., Courrioux, G., & Guillen, A. (2008). Geological modelling from field data and geological knowledge: Part I. Modelling method coupling 3D potential-field interpolation and geological rules. Physics of the Earth and Planetary Interiors, 171(1-4), 147-157.
• Lajaunie, C., Courrioux, G., & Manuel, L. (1997). Foliation fields and 3D cartography in geology: principles of a method based on potential interpolation. Mathematical Geology, 29(4), 571-584.