EMMA is a powerful geophysical electrical and electromagnetic modeling and analysis program. It provides a basis for survey design, instrument development and teaching. EMMA has a user-friendly interface allowing non-experts to calculate responses and perform model parameter analyses with a few clicks of the mouse.

EMMA is freeware. It is provided by Aarhus Geophysics as a design and learning tool for the international geophysical community.

Get EMMA from the download page
EMMA notes (pdf - 6.8 Mb) - getting started document, examples, etc.
EMMA paper (pdf - 5.7 Mb) - paper from Journal of Enviromental and Engineering Geophysics

EMMA - general

In EMMA, you calculate and plot Time Domain Electromagnetic (TEM), Frequency Domain (FEM) and resistivity responses from almost any imaginable source and receiver. The forward modeling and model parameter analysis works for any user-defined instrument configuration. The underlying model is a 1-D model with horizontal layers. Model parameter sensitivity analysis is calculated together with any response. The analysis can be made for different data types - separately or combined. Analyses are also possible for multiple, coupled 1-D models, resulting in pseudo 2-D models. The latter is the so called Laterally Constrained Inversion (LCI) approach.

An advanced forward and inversion algorithm is hidden behind the Windows interface. The non-expert can easily edit a geophysical model and calculate a response and analysis. The expert can set up an advanced configuration or geometry to solve intuitively complicated problems or instrumentation design.

EMMA also offers a variety of functions which can be applied to the calculated responses. E.g. two responses of different configurations, over the same geology can be subtracted to visualize the resulting differences.

EMMA as a learning environment

EMMA is meant to simplify a complicated matter. To build an intuitive understanding of the influence of geology and measurement configuration on model responses and model parameter resolution is a non-trivial task. EMMA gives non-experts access to complicated calculations in a well-known Windows environment. Using the program in a teaching situation gives the students an intuitive understanding of the physics underlying electrical and electromagnetic geophysical methods. EMMA has proven to be a productive learning environment.

Advanced features

For both the TEM and the FEM methods it is possible to model the system response as user-defined bandwidths. As any electrical circuit has a limited bandwidth, this provides a higher degree of realism and more accuracy especially for the earliest times (TEM) or highest frequencies (FEM).

For TEM the waveform is modeled as a piecewise linear approximation, which may be discretized as fine as the user wishes. This allows the user to create complicated waveforms, e.g. a sinc shaped pulse. Furthermore, a noise model, which describes the electromagnetic background noise as a power function, can be stated. This adds further to the simulation of a natural environment or to investigate the influence of a given noise level on the model parameter resolution.

For FEM, the responses can be calculated as real/quadrature or amplitude/phase, and, as for TEM, the sources can be loops, dipoles or wires.