The BIRRP program computes magnetotelluric and geomagnetic depth sounding response functions using a bounded influence, remote reference method, along with an implementation of the jackknife to get error estimates on the result. It incorporates a method for controlling leverage points (i.e., magnetic field values which are statistically anomalous), includes the implementation of two stage processing which enables removal of outliers in both the local electric and magnetic field variables, and allows multiple remote reference sites to be used. The bounded influence statistical algorithm is described in:

    Chave, A.D., and D.J. Thomson, A bounded influence regression estimator based on the statistics of the hat matrix, J. Roy. Stat. Soc., Series C, (Appl. Statist.), 52, 307-322, 2003. (pdf)

The specific extensions required for bounded influence magnetotelluric processing are defined in:

    Chave, A.D., and D.J. Thomson, Bounded influence estimation of magnetotelluric response functions, Geophys. J. Int., 157, 988-1006, 2004. (pdf)

A tutorial on the basic principles of robust spectral analysis may be found in:

    Chave, A.D., D.J. Thomson, and M.E. Ander, On the robust estimation of power spectra, coherences, and transfer functions, J. Geophys. Res., 92, 633-648, 1987. (pdf)

The application of robust methods to magnetotelluric data processing (some of which is updated in the bounded influence reference) is covered by:

    Chave, A.D., and D.J. Thomson, Some comments on magnetotelluric response function estimation, J. Geophys. Res., 94, 14215-14225, 1989. (pdf)

The application of the jackknife to spectral analysis problems is covered in:

    D.J. Thomson and A.D. Chave, Jackknife error estimates for spectra, coherences, and transfer functions, in S. Haykin (ed.), Advances in Spectral Analysis and Array Processing, Englewood Cliffs: Prentice-Hall, pp. 58-113, 1991.

BIRRP is written in Fortran 77 and utilizes only public domain subroutines. The current version is 5.2. Users may need to provide a filter transfer function subroutine as described in the documentation that is specific to their data set.

Documentation for BIRRP in pdf form can be read or downloaded here. An example input data file, filter routine, and output files for a single station taken from the BC87 transect described by Jones et al. (1990) can be downloaded in tar format from here. The raw data used for this example (8 Mb) may be downloaded here in gzipped tar format. Note that these data are in binary format suitable for a big endian machine, and will not read correctly on a little endian (e.g., Intel processor) machine.

Conditions for the use of the BIRRP bounded influence remote reference magnetotelluric processing program:

   1. The robust bounded influence magnetotelluric analysis program, hereinafter called BIRRP, is provided on a caveat emptor basis. The author of BIRRP is not responsible for or culpable in the event of errors in processing or interpretation resulting from use of this code.

   2. No payment will be accepted by any user for data processing with BIRRP.

   3. BIRRP will not be distributed to anyone. Interested persons should be referred to this website.

   4. The author will be notified of any possible coding errors that are encountered.

   5. The author will be informed of any improvements or additions that are made to BIRRP.

   6. The use of BIRRP will be acknowledged in any publications and presentations that ensue.

If these conditions are acceptable, send e-mail to achave@whoi.edu. The body of the message should state "I accept the conditions under which BIRRP is distributed" and copy the above six conditions. A gzipped tar file containing the source code will be distributed by return e-mail.