Tatu Software

Geophysics Electromagnetic Modeling in 1D Layered Media (https://tatusoftware.com)

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Dependencies

• gfortran 8 or later (Fortran 2008)
• GNU Make

How to build

Just run make in the Tatu root directory to create the tatu executable in the same directory.

The Makefile has two targets:

• development (default)
• production

The development target use gfortran flags useful to debug development process and also compile faster. To compile this target use

$ make development

or just

$ make

The production target use gfortran flags that will optimize the executable, making it run faster, but compile slower. To compile this target use

$ make production

How to use

To simulate your models you'll need an input file in JSON (JavaScript Object Notation) format. The code below shows an example input file (input.json) with all required keys:

{
  "transmitter": {
    "model": "vmd",
    "direction": "x",
    "initial": [0, 0, 0],
    "step": 0,
    "final": 0
  },
  "receiver": {
    "direction": "x",
    "initial": [100, 0, 0],
    "step": 0,
    "final": 0
  },
  "frequency": {
    "initial": 1e-1,
    "samples": 1,
    "final": 1e-1
  },
  "layers": {
    "number": 3,
    "resistivity": [100, 500, 10],
    "thickness": [1e2, 50]
  }
}

To simulate this model run

$ ./tatu --input-file input.json --output-file output-name

to get the output in JSON (JavaScript Object Notation) format in a file named output-name.json.

Or run

$ ./tatu --input-file input.json --output-file output-name --output-type ssv

to get the output in SSV (Space-Separated Values) format in a file named output-name.ssv.

Input File Structure

The input file has four sections:

• transmitter
• receiver
• frequency
• layers

Theses sections will contain the information needed to simulate the model. The following shows each one's structure.

transmitter

key	type	description	unit
model	string	the source model name	-
direction	string	the direction to move it at (x, y or z)	-
initial	real array	initial position 3D coordinates	meter
step	real number	position increment step at direction	meter
final	real number	final position at direction	meter

At the moment, tatu supports the following transmitter models:

• hedx (horizontal electric dipole in x direction)
• hedy (horizontal electric dipole in y direction)
• ved (vertical electric dipole)
• hmdx (horizontal magnetic dipole in x direction)
• hmdy (horizontal magnetic dipole in y direction)
• vmd (vertical magnetic dipole)

receiver

key	type	description	unit
direction	string	the direction to move it at (x, y or z)	-
initial	real array	initial position 3D coordinates	meter
step	real number	position increment step at direction	meter
final	real number	final position at direction	meter

frequency

key	type	description	unit
initial	real number	initial value	Hertz
samples	integer number	samples number	-
final	real number	final value	Hertz

The frequency samples are logarithmically interpolated.

layers

key	type	description	unit
number	integer number	layers number	-
resistivity	real array	layers resistivity	Ohm x meter
thickness	real array	layers thickness	meter

The resistivity array length has to be equal the layers number.

The thickness array length has to be equal the layers number minus one.

Output Files Structure

At the moment, the tatu software can save output data in two different formats:

• JSON (JavaScript Object Notation)
• SSV (Space-Separated Values)

JSON format

Output in JSON format contains three sections:

• output (see below)
• input (the input model)
• unique (transmitter, receiver and frequency unique values)

The output section has two subsections:

• labels (array with ordered values labels)
• values (array of values arrays)

The labels array informs the order of the values in each item in values array.

{
  "output": {
    "labels": [
      "transmitter",
      "frequency",
      "receiver",
      "ExReal",
      "ExImag",
      "EyReal",
      "EyImag",
      "EzReal",
      "EzImag",
      "HxReal",
      "HxImag",
      "HyReal",
      "HyImag",
      "HzReal",
      "HzImag"
    ],
    "values": [
      [
        0.0E+0,
        0.10000000000000001E+0,
        0.1E+3,
        0.0E+0,
        0.0E+0,
        -0.28521355723864792E-15,
        -0.6283174409521896E-11,
        0.69358017024460419E+0,
        0.6952704522069525E+0,
        -0.16264080201972775E-12,
        0.22258411762892078E-11,
        0.0E+0,
        0.0E+0,
        -0.79577978723228242E-7,
        -0.5556887181527204E-11
      ]
    ]
  },
  "input": {
    "transmitter": {
      "model": "vmd  ",
      "direction": "x",
      "initial": [ 0.0E+0, 0.0E+0, 0.0E+0 ],
      "step": 0.0E+0,
      "final": 0.0E+0
    },
    "receiver": {
      "direction": "x",
      "initial": [ 0.1E+3, 0.0E+0, 0.0E+0 ],
      "step": 0.0E+0,
      "final": 0.0E+0
    },
    "frequency": {
      "initial": 0.10000000000000001E+0,
      "samples": 1,
      "final": 0.10000000000000001E+0
    },
    "layers": {
      "number": 3,
      "resistivity": [ 0.1E+3, 0.5E+3, 0.1E+2 ],
      "thickness": [ 0.1E+3, 0.5E+2 ]
    }
  },
  "unique": {
    "transmitter": [
      [ 0.0E+0, 0.0E+0, 0.0E+0 ]
    ],
    "frequency": [
      0.10000000000000001E+0
    ],
    "receiver": [
      [ 0.1E+3, 0.0E+0, 0.0E+0 ]
    ]
  }
}

SSV format

Output in SSV format is table-like, in other words presents data in rows and columns. The data in each row follows the same order as shown in JSON format's labels array.

0.00000000000000 0.100000000000000 100.000000000000 0.00000000000000 0.00000000000000 -0.285213557238648E-015 -0.628317440952190E-011   0.00000000000000 0.00000000000000 -0.162640802019728E-012 0.222584117628921E-011 0.00000000000000 0.00000000000000 -0.795779787232282E-007 -0.555688718152720E-011

Options available

To see all options available use

$ ./tatu --help

The output will be something like:

Tatu - Geophysics Electromagnetic Modeling in 1D Layered Media

Usage: tatu [options]

Options (*required):

    -v, --version                   Show version and exit
    -h, --help                      Show this help message
  * -i, --input-file <FILEPATH>     File to read the input data
  * -o, --output-file <FILEPATH>    File to write the output data
    -t, --output-type <FILETYPE>    Output file type: json (default), ssv or all
    -p, --progress                  Show progress