McNeice, G.W. and A.G. Jones, 2001, Multisite, multifrequency tensor decomposition of magnetotelluric data. Geophysics, 66, 158-173.PDF
For more information and discussion, contact Alan Jones at Strike Decomp.
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.
IMPORTANT: In NAG Mark 19 the main minimization routine
we use E04UPF was replaced by
According to the NAG web site, the only change that has to be made is as follows:
E04UPF Withdrawn at Mark 19 Old: CALL E04UPF(M,N,NCLIN,LDA,LDCJ,LDFJ,LDR,A,BL,BU, + CONFUN,OBJFUN,ITER,ISTATE,C,CJAC,F,FJAC, + CLAMDA,OBJF,R,X,IWORK,LIWORK,WORK,LWORK, + IUSER,USER,IFAIL) New: CALL E04UNF(M,N,NCLIN,LDA,LDCJ,LDFJ,LDR,A,BL,BU,Y, + CONFUN,OBJFUN,ITER,ISTATE,C,CJAC,F,FJAC, + CLAMDA,OBJF,R,X,IWORK,LIWORK,WORK,LWORK, + 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.]
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.
Mr. Gary W. McNeice
927 Raftsman Lane,
Ottawa, Ontario, K1C 2V3
Professor Alan G. Jones|
Dublin Institute for Advanced Studies
5 Merrion Square