Tutorial: MT: using EDI files & 1-D modelling

This describes how to use Geophysics MT. You usually work at three nodes in Geophysics > MT: Sounding, Resistivity and Model:

  1. At Sounding: the soundings; each has the location and time of the measurements.
  2. At Resistivity: each sounding's resistivity measurements; GeoData Manager automatically adds impedance measurements to Impedance.
  3. At Model: create one or more 1-D models for each sounding.

Importing EDI files with Add Many

Here we import several EDI files, to create corresponding soundings, impedances and resistivities:

  1. At the node Geophysics > MT > Sounding, right click in the header window (top right):

  2. Click Add Many ...:

    This window has 3 options:

    • Enter location data manually or import from file or spreadsheet: A convenient way to enter several soundings manually, or from a file.

    • Select a folder, import all EDI files and generate impedance and apparent resistivity data sets: Import all EDI files from a folder; create all the corresponding Sounding, Impedance and Resistivity data sets.

    • Import seledted EDI files and generate impedance and apparent resistivity data sets: The same as the previous option, but you can select which EDI files to import.

  3. For now, click the third option to import selected EDI files and click OK:

    Navigate to the folder with your EDI files and select the ones to import. Use the standard windows clicks:

    • Click to select one file.
    • Ctrl+click to select or deselect several files.
    • Shift+click to select a range of files.

    Here, I've selected 3 EDI files to import.

  4. Now click Open:

  5. Click Check, then Apply, then Save:

    Enter an MT resistivity ID for all imported soundings, then click OK. You are done.

  6. You can see the imported soundings at Soundings, Impedances and Resistivities. Here is Resistivities; note the MT Resistivity comment and SourceDataFile:

Note You can also enter a sounding and its measurements manually, one at a time. First create a new sounding, and enter the location and time of the measurements. Then, at Resistivity: add your measurements for the sounding, either by hand or by importing from a spreadsheet.

Working with MT 1-D models

This shows how to use GeoData Manager's 1-D modeller to create a 1-D model for the sounding:

  1. At the node Geophysics > MT > Model, right click in the header window (top right) and click New:

  2. Find the sounding name in the list, click it and click OK.

  3. Enter the identifiers for the new model and click OK. GeoData Manager creates a new model, with no resistivities or depths:

  4. Click to start the 1-D modeller.

    If you get an error like this see Measured resistivity data below:


    The modeller:

    Change the model's resistivities and depths until the model's apparent resistivity and phase curve matches the measured apparent resistivity and phase data. Click Help in the modeller to get help for using the modeller.

  5. Click Done when you are satisfied with the model. The modeller stores the model's resistivities and depths in the dataset:

Measured resistivity data