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MARE2DEM: Modeling with Adaptively Refined Elements for 2D Electromagnetics
MARE2DEM (pronounced mahr-ey 2DEM) is a parallel adaptive finite element code for 2D forward and inverse modeling for electromagnetic geophysics. Initially developed with funding support from the Scripps Seafloor Electromagnetic Methods Consortium, it is now supported by the Electromagnetic Methods Research Consortium at Columbia University. New features are made exclusively available to consortium sponsors for a period of time and later are released publicly.
MARE2DEM works for 2D anisotropic modeling for controlled-source electromagnetic (CSEM), magnetotelluric (MT) and surface-borehole EM applications in onshore, offshore and downhole environments. The main benefits of MARE2DEM are:
Fully automatic unstructured mesh generation so that end-users are free from the burden of designing numerically accurate grids for complicated models.
Interactive graphical user-interface for designing models and viewing results.
Open-source license and freely available.
General Features and Capabilities
Forward calculations using fully automatic goal-oriented adaptive finite elements
Non-linear inversion using a fast parallel implementation of Occam’s method, a regularized Gauss-Newton minimization technique
Magnetotelluric (MT) plane waves using total field or scattered field implementations
Frequency domain marine, land and borehole 2.5D EM modeling (2.5D means 3D source field in 2D geometry)
Arbitrary locations and rotations for receivers and transmitters
Support for point or finite length dipole wires for both transmitters and receivers
Efficient inversion of long lines of towed-streamer marine EM data using moving footprint windows
Support for isotropic, transversely isotropic, triaxial anisotropic or isotropic complex conductivity
Inverted conductivity parameters can be bounded using non-linear transforms
Parallel data decomposition for a nearly linear speedup with the number of processors.
Dense matrix operations during inversion are efficiently handled in parallel using the ScaLAPACK library
Can be run in parallel on 1000’s of processors for efficient inversion of large CSEM data sets
Can be run on laptops for MT or lightweight CSEM applications.
MATLAB Model builder interface (Mamba2D) for building forward models with arbitrarily complex 2D structures, and inversion parameter grids with unstructured triangular meshes or conforming quadrilateral grids. Also supports nested gridding (e.g. for near-surface small scale features).
MATLAB 2D model plotting routines allow for overlaying geologic layers, seismic reflection images and well logs, plotting normalized inversion sensitivity, etc.
If you publish results made using MARE2DEM, please consider citing [Key16]:
Key, K., 2016, MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data. Geophysical Journal International, 207(1), 571–588. DOI: 10.1093/gji/ggw290.
Kerry Key, Lamont-Doherty Earth Observatory, Columbia University http://emlab.ldeo.columbia.edu
Interested in contributing? Contact us!
MARE2DEM is made freely available under the GNU GPLv3 license.
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. 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 wavenumber domain differential equations. These collaborations resulted in publications and early adaptive finite element forward codes named MARE2DMT [KeWe06] and MARE2DCSEM [LiKe07]. 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 uses the following code packages and their authors are greatly acknowledged for making these codes freely available: