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JOINTEM


Version 1.4a (c) 2014 by Markku Pirttijärvi.

JOINTEM is geophysical modelling and interpretation software for:

  1. geoelectrical dc soundings, a.k.a. vertical electric soundings (VES),
  2. time-domain electromagnetic (TEM) soundings (single and central loop),
  3. audiomagnetotelluric (AMT) soundings based on plane wave impedance, and
  4. frequency-domain VLF-R measurements (single frequency).

The computation is based on one-dimensional (1-D) horizontally layered earth model. The model parameters are the electrical resistivity and thickness (or depth to the top) of the layers. Cole-Cole model parameters (chargeability, frequency factor, and time constant) can be used in TEM method to account for (induced) polarization and dispersion effects and the chargeability can be utilized in DC soundings. Optimization based on linearized inversion method with adaptive damping is used to minimize the difference between measured field data and synthetic data computed for the model. Both individual and joint inversion of DC, TEM, and AMT data is possible. VLF-R data measured at single frequency can be used as additional constraint.

Screen dump of the JOINTEM program

The JOINTEM program is a 32-bit application that can be run on Windows XP, Vista or 7 with a graphics display resolution of at least 1280x1024 pixels. Memory requirements and processor speed are not critical, since large data sets are not used and the computations, which are based on a convolution algorithms and direct analytical solutions for layered earth models, allows fast computation even on older computers. JOINTEM has simple graphical user interface (GUI) that can be used to change the parameter values, to handle file input and output, and to visualize the data and the model responses and the model. The GUI and graphics are based on the DISLIN graphics library (http://www.dislin.de).

Download the JOINTEM.ZIP package (2.6 MB).

To install JOINTEM simply unzip (Pkzip/Winzip) the distribution file (JOINTEM.ZIP) into a new folder. You can also create a shortcut on the desktop but in this caseyou should take care that the start in folder is the same as the program folder. Otherwise, some extra files will appear on the desktop too. The distribution file contains the 32-bit executable (JOINTEM.EXE), a short description file (_README.TXT), user's manual (JOINTEM_MANU.PDF), and some example data and model files (*_DC.DAT, *_TEM.DAT, *_AMT.DAT & *_.INP).

User's guide (JOINTEM_MANU.PDF) (1.9 MB).


Version 1.3 from August 2009 introduces AMT method, VES apparent chargeability and TEM central loop system, several GUI enhancements and several other changes.
Update 1.3a fixes incorrectly set depths when depth mode was used instead of thickness, AMT phase and VES charegeability autosizing was changed too.
Version 1.4 from November 2010 fixes VES computation for strong conductivity contrasts.
Update 1.4b from January 2014 fixes data normalization and the user manual now defines the correct syntax for TEM systems (IMOT).

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3 Comments

  1. A severe error was found from DC/VES computation in version 1.3.The convolution filter fails when the top layer is highly resistive. The whole DC computation algorithm needs to be changed.

  2. Version 1.4 fixes the DC computation by using proper fast Hankel transform algorithm (convolution and optimized filter coefficients). TEM filters were updated also.

  3. The user manual defined TEM data incorrectly, the IMOT variable should be 1 or 2 for single loop data (voltage or rhoa) and 3 or 4 for coindicent loop data (voltage or rhoa).