3.2.2. Forward Input File

The forward problem is solved using the executable program h3dtd_v2.exe. The lines of input file are as follows:

Line #	Description	Description
1	Tensor Mesh	path to tensor mesh file
2	Conductivity Model	conductivity model
3	Susceptibility Model (optional)	susceptibility model
4	Locations File	defines the survey geometry
5	Waveform File	defines transmitter waveform and time-stepping
6	Time Gates File	defines the observation times for predicted data
7	Solver	choose Pardiso or MUMPS solver
8	Memory Options	store factorizations in RAM or write to disk

Fig. 3.2 Example input file for the inversion program (Download ).

3.2.2.1. Line Descriptions

• Tensor Mesh: file path to the tensor mesh file

• Conductivity Model: Defines the conductivity model for the forward problem. There are two options:

  • FILE filepath: The user enters the flag FILE followed by the path to the conductivity model file

  • VALUE val: The user enters the flag VALUE followed by a value representing the conductivity of a wholespace model; e.g. we are modeling a wholespace if this option is used.

• Susceptibility Model: Defines the conductivity model for the forward problem. There are two options:

  • 0: A flag of 0 is entered if the susceptibility within the domain is zero

  • FILE filepath: The user enters the flag FILE followed by the path to the susceptibility model file

  • VALUE val: The user enters the flag VALUE followed by a value representing the susceptibility of a wholespace model; e.g. the same susceptibility value is assigned to every cell

• Locations File: Provide the path to the locations file

• Wave File: Provide the path to the wave file. This file defines the transmitter current and time-stepping for the problem.

• Time Gates File: Provide the path to the time gates file. This file defines the times at which the TEM data are measured for the forward problem.

• Solver: Define the direct solver that will be used to factor and solve linear systems. Enter one of the following flags:

  • FACTOR_PARDISO: Factor and solve linear systems with Pardiso solver

  • FACTOR_MUMPS: Factor and solve linear systems with MUMPS solver

• Memory Options: Enter one of the following flags:

  • FACTOR_IC: Store factorization in the computer’s RAM. This options is much faster but can only be used on problems of a reasonable size

  • FACTOR_OOC: Writes the factorizations of linear systems to disk. Slower but capable of solving much larger problems.