3.2.3. Forward Modeling Input File

The forward problem is solved using the executable program e3dmt_fwd.exe. Parameters necessary for running the forward modeling code are set in the input file. The lines of input file are as follows:

Line #

Parameter

Description

1

OcTree Mesh

path to octree mesh file

2

Receiver Locations

path to observation locations file

3

Real Conductivity

path to conductivity model

4

Imaginary Conductivity

path to imaginary conductivity file (optional)

5

1D Background Conductivity

set 1D conductivity model

6

Background Susceptibility

set background susceptibility

7

Topography

set topography
../../_images/create_fwd_input.png

Fig. 3.4 Example input file for forward modeling program (Download ).

3.2.3.1. Line Descriptions

  • OcTree Mesh: file path to the OcTree mesh file

  • Real Conductivity: file path to the conductivity model. If complex conductivities are being used, this model represents real-valued conductivities.

  • Imaginary Conductivity: If the conductivity model used in the forward simulation is strictly real-valued, the user may enter “NO_IMAG_COND” on this line. Otherwise, the user enters the file path to the imaginary conductivity model.

  • 1D Background Conductivity: The user may supply the file path to a 1D background conductivity model . If a homogeneous background conductivity is being used, the user enters “VALUE” followed by a space and a numerical value; example “VALUE 0.01”

Important

  • The number of layers in the 1D model for E3DMT must equal the number of underlying mesh cells in the vertical direction. Thus if underlying mesh for the OcTree mesh is 1028 by 1028 by 512, the 1D model must have 512 layer conductivities.

  • The boundary conditions computed using 1D models is only accurate when surface topography is minimal. In the case where surface topography is significant, it is suggested the user used E3DMT version 2.

  • Background Susceptibility: The user may provide the file path to a background susceptibility model on this line. If a constant susceptibility is being used, “VALUE” may be entered and followed by the background susceptibility. For no background susceptibility, the flag “NO_SUS” is used.

  • Topography: The user may supply the file path to an active cells model file or type “ALL_ACTIVE”. The active cells model has values 1 for cells lying below the surface topography and values 0 for cells lying above.