Steven
D. Sheriff
Professor & Chair
Geology Department
University of Montana
email: gl_sds@selway.umt.edu
Office: 4062436560
Fax: 4062434028
Over
the years I have written a number of programs, Mathcad documents and
spreadsheets. Some have been for teaching, others for research, recreation
or commercial purposes. A number of them can be downloaded using the
links below. They are available for your use in education (personal
and public). If you use them for commercial purposes or have money to
spare please contact me to purchase them. If they are useful for educational
purposes  drop me (or
my Dean...) a note. They are not available for resale and they come
"as is" with no warranty or promised support. At the bottom
of the page are some notes on using software and CDs we have in the
lab.
The
following are DOSbased programs. Although they allow graphical
interaction for model building they do not use the mouse. Printing is
fullscreen

GravCad
is a 2D gravity modeling program. The lower window shows the geologic
model, the upper window shows the gravitational response.

MagCad
is a 2D magnetic modeling program. The lower window shows the geologic
model, the upper window shows the magnetic response. MagCad will calculate
magnetic gradient as well as total field and allows for remanence
as well as induced magnetization.

Sounder
is a 1D electrical resistivity modeling and inversion program for
Wenner and Schlumberger arrays.

80toXYZ
is a program we use to parse NOAA and DMA gravity data off of their
CD ROM.

Dig&Filt
allows interactive visualization of Fourier transforms and many different
filtering operations.

Spliner
can be used to demonstrate problems that develop with undersampling
of data.
The following
are MSwindows programs:
 GravCadW
is an eventdriven 2D gravity modeling program which includes nonlinear
(MarquardtLevenberg) inversion. You may need the full setup/install
system but you might get by with just
the .exe if you have the
correct MS DLL libraries already installed. There are a few known bugs
in GravCadW including:
 The print routine
will crash if you stack vertices (give them the same xvalues).
 Model/profile
widths must be < 2^15 units wide.
 Many features
of the windows models are not saved when you save the models in
the DOS format and I have not written the Windows save routines
(yet...).
 PFdriver
is a program that allows rapid conversion between 80toXYZ
files, USGS potential field grids, and SURFER's
file format.
 Invert
demonstrates nonlinear regression/inversion for gravity data using a
buried sphere. The user can choose to allow x, z, and/or density to
change and step through iterations one by one.
The following
are MathCad documents  again, no guarantees...
 Cooling
Dike  quick and dirty solution of simple conductive cooling.
 Cooling
Sill  quick and dirty solution of simple conductive cooling.
 Grav
Inverse  demonstrates nonlinear leastsquares inverse problems.
 Exponential
error  shows pitfalls regarding, error analysis, of fitting lines
in Log space.
 Vibroseis
 shows how do think about (and calculate) synthetic seismograms using
convolution and correlation in MathCad.
 Geotherm
shows how to calculate a simple1D geotherm
And finally
a few spreadsheets:
 Synseis
demonstrates convolution with a spreadsheet and produces a simple synthetic
seismogram to demonstrate the idea..
 2Spheres
shows the gravitational effect of moving two spheres progressively deeper
into the subsurface  anomalies get broader and merge. This works well
to help understanding of wavelength vs depth in potential field anomalies.
 FAA
Density shows how to calculate the average density of local terrain
using the Free Air Anomaly (FAA and topography)  a variant of Nettleton's
technique.
 Schlum
shows how to forwardmodel electrical sounding experiments for a Schlumberger
array using convolution on a spreadsheet. The details are in: S.D. Sheriff,
1992, Spreadsheet modeling of electrical sounding experiments. Ground
Water, v 30 #6, 971974. Here's a draft
of the manuscript.
 3
point drill hole finds the dip vector from three {x, y, z} points.
From there it calculates the apparent thickness of a bed pierced by
a drill hole with given bearing and plunge. And it allows for determining
the true thickness
given the apparent thickness.
 Stereonet
shows how to trick Excel into plotting directions on a stereonet.
Notes and
comments on lab CDs & software
Getting aeromagnetic
data off the Former Soviet Union Aeromag CD


Geosciences Department  The University of Montana  32 Campus Drive #1296  Missoula, MT 598121296
Phone: (406) 2432341 Fax: (406) 2434028 Email: geology@mso.umt.edu
Layout and Design by Brian W. Collins, updates and current content by Aaron Deskins ©2005/2008
The University of Montana Geosciences Department