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Occam's inversion for 2D magnetotelluric (MT) modeling

Version 3.0 is a major update to Occam 2DMT and is significantly faster than version 2.0. Thanks to Marine EM Laboratory graduate student David Myer for moving the code to Fortran 90. Thanks also to Patricia deLugao and Phil Wannamaker for providing fast derivative computations using reciprocity.

New Features in Version 3.0:

  • Fortran 90 source code using dynamic memory allocation and fast array math
  • Backward compatible with previous file formats
  • Derivatives are now calculated using reciprocity (deLugao and Wannamaker, 1996), resulting in a tremendous speed-up.
  • Flexible input format for startup file
  • Roughness operator options: simple first-difference penalties, diagonal penalties, relative weighting between horizontal and vertical penalties, depth-weighted penalties, aspect ratio weighted penalties
  • Optional command line input argument for computing forward response only
  • Optional command line argument for starting from an iteration file named something other than "startup"
  • Optional model resistivity limits. Imposes limits on minimum and maximum resistivity
  • Optional model parameter discrete step size. Forces resistivity to vary at discrete steps
  • Data types supported: apparent resistivity, phase, impedances, and magnetic field tipper
  • Matlab routines for plotting models, penalty cuts, prejudiced parameters, model responses, pseudosections, profiles, misfit curves.

Download a zip archive of the code with examples:

OCCAM2DMT_V3.0.zip (1.26 MB)

Download the Matlab plotting tools written by Kerry Key:



Occam's Inversion:

Constable, S. C., R. L. Parker, and C. G. Constable, Occam’s inversion - A
practical algorithm for generating smooth models from electromagnetic sounding data, Geophysics, 52 (03), 289–300, 1987.

deGroot-Hedlin, C., and S. Constable, Occam’s inversion to generate smooth two-
dimensional models from magnetotelluric data, Geophysics, 55 (12), 1613–1624, 1990.

2DMT Forward code:

Wannamaker, P. E., J. A. Stodt, and L. Rijo, A stable finite-element solution for
two-dimensional magnetotelluric modeling, Geophysical Journal of
the Royal Astronomical Society, 88, 277–296, 1987.

2DMT Jacobian sensitivity code:

de Lugao, P. P., and P. Wannamaker, Calculating the two-
dimensional magnetotelluric Jacobian in finite elements using reciprocity,
Geophys. J. Int., 127, 806-810, 1996.

Last updated: Saturday, 16-Mar-2013 16:29:09 PDT
email: sconstable@ucsd.edu