MARE2DEM (pronounced* mahr-ey 2DEM*) is a parallel adaptive finite element code for 2D forward and inverse modeling for electromagnetic geophysics. It was developed with funding support from the Scripps Seafloor Electromagnetic Methods Consortium. After a period of exclusive access for consortium members, the code is now being made freely available. MARE2DEM was originally designed with marine controlled-source electromagnetic (CSEM) and marine magnetotelluric (MT) applications in mind, but it can also be applied to onshore electromagnetic modeling problems. Two main features of MARE2DEM are (1) it uses fully automatic mesh generation so that end users are free from the burden of designing numerically accurate grids for complicated models and (2) it is open-source and freely available. The code package has reached a fairly mature state, but there are several planned new features and development is ongoing, so stayed tuned for updates.

##### Features:

- Forward calculations using fully automatic goal-oriented adaptive finite elements
- Non-linear inversion using a new faster implementation of Occam’s method
- Models electric & magnetic dipoles and magnetotelluric (MT) plane waves
- Models marine, land and borehole transmitters and receivers (but is not yet configured for airborne EM)
- Models point or finite length dipole wires
- Models isotropic, transversely isotropic or triaxial anisotropic conductivity
- Inverted conductivity parameters can be bounded using non-linear transforms
- Run in parallel on laptops to large clusters. The forward code uses a parallel data decomposition for a nearly linear speedup with the number of processors. The inversion code performs dense matrix operations efficiently in parallel using the ScaLAPACK library.
- Model Builder Assistant (Mamba2D) for MATLAB
- Inversion model and response plotting tools for MATLAB
- Open source under the GNU GPL license
- Languages: Fortran (modern), C, MPI. Requires the
**Intel**C and Fortran compilers.

##### References:

The isotropic forward code is described in:

Key, K., and Ovall, J. (2011). A parallel goal-oriented adaptive finite element method for 2.5-D electromagnetic modelling *Geophysical Journal International*, *186*(1), 137–154. doi:10.1111/j.1365-246X.2011.05025.x

The anisotropic forward code and some of the inversion code approaches are described in:

Key, K. (2012). Marine EM inversion using unstructured grids: a 2D parallel adaptive finite element algorithm. *SEG Technical Program Expanded Abstracts 2012*, 1–5. doi:10.1190/segam2012-1294.1

A new manuscript on the anisotropic inversion code is pending.

##### Acknowledgments:

The following people are thanked for helpful discussions or for directly contributing to the package of MARE2DEM codes: David Alumbaugh, Steven Constable, Mike Hoversten, David Myer, and Jeff Ovall. In particular, David Myer, former Scripps PhD student and now a consultant at BlueGreen Geophysics, continues to make useful contributions to the MARE2DEM codes. I also extend gratitude to Chet Weiss, who first taught me about finite element methods during his visiting appointment at Scripps in 2003, and to Yuguo Li, who came to Scripps as a Postdoc in 2004 and showed me that the 2.5D CSEM problem isn't so bad, despite a heinously complicated set of coupled differential equations. These collaborations resulted in publications and early adaptive finite element forward codes named MARE2DMT and MARE2DCSEM. Finally, Steve Constable is thanked for many useful discussions about Occam's inversion and for making the original Occam codes (1D and 2D MT) freely available; the public release of MARE2DEM is an attempt to follow in these footsteps.

MARE2DEM relies on the following libraries and their authors are acknowledges for making them freely available: