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 speedup.
 Flexible input format for startup file
 Roughness operator options: simple firstdifference penalties, diagonal
penalties, relative weighting between horizontal and vertical penalties,
depthweighted 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:
OCCAM2DMT_Matlab.zip
References:
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.
deGrootHedlin, 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 finiteelement solution
for
twodimensional 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, 806810, 1996.
