Strike Code Page: version 6.1

Multi-site, multi-frequency (or now multi-depth, v6+) distortion decompsition of magnetotelluric data based on:

McNeice, G.W. and A.G. Jones, 2001, Multisite, multifrequency tensor decomposition of magnetotelluric data. Geophysics, 66, 158-173.PDF

Latest publicly available version and build date: 6.1: 30 MAY 2014

Versions 6+ have the option to solve in approximate depth windows instead of only period windows. This is very useful when the penetration depth changes significantly along the profile or within your array, and you want to undertake multi-site analysis.
An example is give in:
Miensopust, M., A.G. Jones, M.R. Muller, X. Garcia, and R.L. Evans, 2011.
Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed through magnetotelluric profiling as part of the Southern African Magnetotelluric Experiment.
Journal of Geophysical Research - Solid Earth, 116, B02401, doi:10.1029/2010JB007740. [PDF]

For more information and discussion, contact Alan Jones at Strike Decomp.

Strike is the multi-site, multi-frequency magnetotelluric tensor decomposition code written by Gary McNeice and Alan Jones.

It is based on Groom-Bailey tensor decomposition. It currently solves for the electric effects of the galvanic-charges only. Tests with including magnetic effects (see McNeice and Jones, 2001) show the inherent instability of trying to solve for so many parameters.

Documentation can be read here. An example input data file from a single station can be downloaded from here, and an output file for one-decade-width bands from here.

The input data must be in either J-format or EDI-format. The program will either read in a single data file (for single-site mode), or read in a list of data files (for multi-site mode). The user specifies frequency bands to operate on, and an overlap. Accordingly, mixed datasets are permitted with data at different frequencies at different sites.

Strike is written entirely in FORTRAN77. The current version calls Numerical Algorithm Group (NAG) F77 routines (up to Mark 18) for solving the problem. The user is responsible for owning a licence from NAG (either for the PC or for Unix) and for replacing the Mark 16 calls with calls to the latest version of NAG (which I don't have).

IMPORTANT: In NAG Mark 19 the main minimization routine we use E04UPF was replaced by E04UNF.
According to the NAG web site, the only change that has to be made is as follows:

Withdrawn at Mark 19

         +            IUSER,USER,IFAIL)
         +            IUSER,USER,IFAIL)

E04UNF contains one additional parameter as follows:

     Y(M) - real array.

Note that a call to E04UPF is the same as a call to E04UNF with Y(i) = 0.0, for i = 1,2,...,M.

but I have not tested this. If you use Mark 19 and test this replacement, please let me know that it works.

We have attempted to find alternative freeware routines for the minimization search, but we have found the NAG routines to be stable and fast compared to any others. Also, the NAG routine is the only one we know of that permits the user to supply the Jacobian and the Hermetian matrices, as well as have bounds on the model parameters.
Note that we are using a routine that is no longer available in the current versions of NAG releases.
[We would be willing to work with someone who is prepared to test out other routines so we would no longer be dependent on NAG.]

The following are the conditions under which you are permitted to use the code "strike", written by Gary McNeice and Alan Jones, for the tensor decomposition of magnetotelluric data. To obtain the code, please sign and date your acceptance of these conditions, and send a scan of the form to Alan Jones ( - replace "-at-" with "@").
Please put "strike" as the first word in the header to your email request.

We ask you to do this not to restrict use of strike in any way, but to ensure that each user acknowledges the terms for its use, that we know who is using it so you will be informed immediately of bugs and new releases, and to try to ensure that it is freely available to those who use it for free. Commercial use is certainly encouraged - please contact Alan Jones to discuss licencing terms.

Note: Each person who wished to use strike must send in a scanned signed document agreeing to these terms. That includes all students as well as their supervisors.

A list of official strike users can be viewed here. If you are using strike, and are not on that list, then you must register your usage by sending a scanned signed form to Alan Jones as described above.

Conditions for the use of the McNeice-Jones multi-site, multi-frequency magnetotelluric tensor decomposition code.

  1. I accept the McNeice-Jones multi-site, multi-frequency magnetotelluric tensor decomposition code, hereinafter called "strike", on a caveat emptor basis.
  2. I will use strike for non-profit purposes only.
  3. I will not accept any payment for use of strike.
  4. I will not give strike to any other person.
  5. I will inform the authors of strike, Gary McNeice and Alan Jones, of any coding errors that I find.
  6. I will inform the authors of strike, Gary McNeice and Alan Jones, of any improvements and additions that I make.
  7. I will acknowledge the use of strike in any publications and presentations I write or give in which I present results based on strike-based decomposition or decomposed data.
  8. I understand that the current version of strike, v6.1, uses NAG v16 routines that I have to supply myself or have to replace with newer versions.

Signed:____________________________________ Date:_________________

Street Address:
Postal Code:

Email address:

Anyone who wishes to use strike for commercial or profit or payment purposes please contact Alan Jones at Strike Decomp (replace "-at" with "@") to discuss licencing terms.


Mr. Gary W. McNeice
927 Raftsman Lane,
Ottawa, Ontario, K1C 2V3
Email: gwmcneice -at-
Professor Alan G. Jones
Complete MT Solutions
5345 McLean Crescent
Manotick, Ontario
Canada, K4M 1E4
Email: alan.jones.geophysics -at-
Please do NOT send an email directly to either author. Send all messages to strike.decomp -at-

MTNet Home Page Alan's Home Page

Alan G Jones / 25 July 2016 /