.. image:: ./_static/emsig-logo.svg
   :width: 400 px
   :align: center
   :alt: emsig logo
   :target: https://emsig.xyz
   :class: dark-light

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========================================
ElectroMagnetic Simulation in Geophysics
========================================

**emsig** are open-source codes to simulate electromagnetic data. Their main
targets are geophysical applications (exploration and monitoring, engineering,
environmental), but they are by no means limited to that. Currently there are
two main codes, `empymod <https://empymod.emsig.xyz>`_ and `emg3d
<https://emg3d.emsig.xyz>`_. The former is a 3D code for layered media, the
latter is a low-memory multigrid solver for 3D media. Both are written in
`Python <https://www.python.org/>`_ and released under the permissive
`Apache-2.0 license <https://www.apache.org/licenses/LICENSE-2.0>`_.


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.. grid:: 1 2 2 2
    :gutter: 2

    .. grid-item-card::
        :img-top: _static/empymod-logo.svg

        3D EM modeller for 1D VTI media
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

        .. button-link:: https://empymod.emsig.xyz
            :expand:
            :color: info
            :click-parent:

            empymod.emsig.xyz

        The modeller **empymod** can compute electric or magnetic responses due
        to a 3D electric or magnetic source in a layered-earth model with
        vertical transverse isotropic (VTI) resistivity, VTI electric
        permittivity, and VTI magnetic permeability, from very low frequencies
        (DC) to very high frequencies (GPR). The computation is carried out in
        the wavenumber-frequency domain, and various Hankel- and
        Fourier-transform methods are included to transform the responses into
        the space-frequency and space-time domains.

        ++++++

        .. code:: bash

            pip install empymod

        .. code:: bash

            conda install -c conda-forge empymod

    .. grid-item-card::
        :img-top: _static/emg3d-logo.svg

        Multigrid solver for 3D EM diffusion
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

        .. button-link:: https://emg3d.emsig.xyz
            :expand:
            :color: info
            :click-parent:

            emg3d.emsig.xyz

        The modeller **emg3d** is a multigrid solver for 3D EM diffusion with
        tri-axial electrical anisotropy. The matrix-free solver can be used as
        main solver or as preconditioner for Krylov subspace methods, and the
        governing equations are discretized on a staggered Yee grid.

        ++++++

        .. code:: bash

            pip install emg3d

        .. code:: bash

            conda install -c conda-forge emg3d

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:fa:`fas fa-users fa-2x` Contributing & Contact
-----------------------------------------------

**emsig** are community codes, please help to shape their future!

.. grid:: 1
    :gutter: 2

    .. grid-item-card::

        :fa:`fab fa-github fa-2x`
        `Submit bugs, fix typos, contribute code, and so much more!
        <https://github.com/emsig>`_

    .. grid-item-card::

        :fa:`fab fa-slack fa-2x`
        Join the **#emsig**-channel either on `SWUNG
        <https://swu.ng/slack>`_ or on `SimPEG <http://slack.simpeg.xyz>`_.

    .. grid-item-card::

        :fa:`far fa-envelope fa-2x`
        If you prefer personal email you can contact me through
        my website `werthmuller.org. <https://werthmuller.org/contact/>`_

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Related ecosystem
=================

**emsig** and its codes **empymod** and **emg3d** are part of a bigger, fast
growing, open-source **EM & Potential Geo-Exploration Python Ecosystem**:

.. raw:: html

   <p style="line-height:10em">

   <a href=https://pygimli.org><img src="https://www.pygimli.org/_static/gimli_logo.svg" style="max-height: 2cm;"></a>

   <a href=https://simpeg.xyz><img src="https://raw.github.com/simpeg/simpeg/master/docs/images/simpeg-logo.png" style="max-height: 2.5cm;"></a>

   <a style="margin:1em" href=https://petgem.bsc.es><img src="https://petgem.bsc.es/_static/figures/petgem_logo.png" style="max-height: 3cm;"></a>

   <a href=https://gitlab.com/Rochlitz.R/custEM><img src="https://custem.readthedocs.io/en/latest/_static/custEMlogo.png" style="max-height: 1.5cm;"></a>

   <a href=https://docs.pyvista.org><img src="https://raw.githubusercontent.com/pyvista/pyvista/main/doc/source/_static/pyvista_logo_sm.png" style="max-height: 2.5cm;"></a>

   <a style="margin:1em" href=https://www.fatiando.org><img src="https://raw.github.com/fatiando/logo/master/fatiando-logo-background.png" style="max-height: 3cm;"></a>

   <a href=https://www.gempy.org><img src="https://raw.github.com/cgre-aachen/gempy/master/docs/source/_static/logos/gempy.png" style="max-height: 2.5cm;"></a>

   <a style="margin:1em" href=https://softwareunderground.github.io/subsurface/><img src="https://raw.github.com/softwareunderground/subsurface/main/docs/source/_static/logos/subsurface.png" style="max-height: 3cm;"></a>

   <a href=https://hkex.gitlab.io/resipy><img src="https://hkex.gitlab.io/resipy/_static/logo.png" style="max-height: 3cm;"></a>

   <a href=https://hkex.gitlab.io/emagpy><img src="https://hkex.gitlab.io/emagpy/_static/logo.png" style="max-height: 3cm;"></a>

   <a href=https://emsig.xyz><img src="https://emsig.xyz/_static/emsig-logo.svg" style="max-height: 2cm;"></a>

   <a href=https://mtpy2.readthedocs.io"><big>&nbsp;&nbsp;MTpy&nbsp;&nbsp;</big></a>

   </p>

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.. dropdown:: About the name and logo of emsig

    The name **emsig** is an abbreviation in English and a pun in German.

    It stands primarily as abbreviation for ElectroMagnetic Simulation in
    Geophysics. However, **emsig** is also a German adjective, meaning
    *hard-working* or *diligent*. Surely, our codes make our computers work
    hard!

    Finally, moving to the logo, the **sig**-ending can be seen as the short
    form of **sigma**, the symbol generally used for conductivity in
    geophysics, one of the elementary properties in electromagnetic modelling.
    The «s» in the logo of **emsig** is denoted by «ς», a variation of «σ»
    (sigma) in the Greek alphabet.

    The symbol itself represents the perpendicularity of electric and magnetic
    fields.

    .. image:: ./_static/emsig-logo.svg
        :class: dark-light