Temix & Temix XL 
Transient Electromagnetic Sounding with Mapping and
Profiling
General
TEMIX and TEMIX XL interpret
electromagnetic sounding data taken with the transient
electromagnetic (TEM) method. These software packages
allow for the forward and inverse modeling of TEM data
acquired in terms of 1D sounding curves. TEMIX & TEMIX
XL run in protected mode on 386, 486 and Pentium based
machines with standard math coprocessor.
Both packages in the TEMIX family
produce forward and inverse results using layered earth
models for transient EM data collected with a variety of
commonly available field instruments. The base version,
TEMIX, has the same interpretational capabilities as
TEMIX XL, but does not have the interactive mapping and
profiling capability. The new consolidated TEMIX
replaces the previous series of five TEMIX v3 packages,
with additional enhancements. The features of TEMIX Plus
have been incorporated in the mapping and profiling
features of TEMIX XL.
TEMIX computes the forward model
using an Anderson style digital filtering technique to
carry out the Hankel and Fourier transforms. FittermanAnderson
style integrations account for the ramp time. Rather
than removing effects from the observed data, TEMIX
takes the calculated curves and applies corrections for
previous pulse (also known as runon) and ramp turnoff
time.
The inversion process uses the
Inman style ridge regression approach of nonlinear
least squares curve fitting. Prior to inversion, you may
constrain parameters of the starting model so that they
will not be adjusted by the inversion algorithm, or so
that their adjustment is limited.
The TEMIX family is a pair of
interactive, graphically oriented, forward and inverse
modeling programs for interpreting transient
electromagnetic (TEM) data in terms of a layered earth
(1D) model.
Geometries available are Central
Loop, Coincident Loop, Fixed Loop and Grounded Wire.
Different geometries and instruments can be mixed
together in a single database.
Sounding curves are entered as a
function of time. Where applicable to the selected
instrument, interactive worksheets are provided for
reducing the measurements taken directly from the
respective instruments. The output, in terms of
normalized received voltage versus time, interfaces
directly with the rest of the program, and is
transparent to the user.
Forward modeling allows the user to
calculate a synthetic electromagnetic sounding curve for
a model with up to ten plane layers. Electromagnetic
sounding curves are calculated using filters designed by
Anderson, 1979 (USGS Open File Report 79590). The
forward modeling routines have been optimized to provide
great computational speed and increased accuracy.
Forward modeling calculations use an equivalent dipole
approximation after Stoyer, 1990. (Geophysical
Prospecting, 38, 8799)
Model parameters (resistivity and
depths or thickness) can be entered numerically or
graphically. With graphical entry, TEMIX automatically
performs conversions between time and depth using the
average conductivity of the model and the diffusion
depth formula.
Ramp times are accounted for by
convolving the turnoff ramp with the synthetic curve
for the specific layered model as described by Fitterman
and Anderson (1987). Runon, the influence of previous
turnon and turnoff cycles in the transmitter wave
train, is accounted for by summing the transient voltage
from delayed pulses, according to the user's
specification.
Inverse modeling allows you to
obtain a model that best fits the data in a least
squares sense. This is done by using ridge regression
(Inman, 1975, Geophysics, 40, pp 798817) to iteratively
adjust the parameters of a starting model supplied by
the user. You can constrain some of the starting model
parameters so the inversion will not adjust them.
Starting models for inversion can have up to 8 layers.
Forward models can have as many as 10 layers.
Constraints can be applied by fixing (or freezing) a
parameter, or by imposing limits on a parameter.
Masking enables the user to keep
"bad" or unwanted data points as part of the data set,
while excluding them from Forward (percent error) and
Inverse calculations.
Suites of forward models, for which
field recording or model parameters are varied, enable
you to clearly see the effect of such variations on the
sounding curve.
Equivalence analysis enables you to
generate a set of equivalent models, that is,
alternative models that fit the data nearly as well as
the bestfit model, but differ from this model.
Equivalence analysis is done by using the parameter
resolution matrix to show the linear combinations of
model parameters that are unknown. Also, the forward
calculations for each model are used; these are selected
to determine the extent to which modifications to the
model can be made according to these guidelines without
exceeding a userspecified error. Equivalence analysis
also indicates the allowable range of each of the model
parameters.
Advanced batch processing allows
the user to set flags for forward, inverse, smooth and
equivalent models. Batch execution then uses these flags
to determine which soundings to include in the batch
process. Flags are set in a spreadsheet like editor.
Batch processing also features a
batch fix and substitute command to fix inversion
parameters for groups of models. This also allows for
setting of a starting model for a whole group of
soundings.
Batch Plotting of all soundings in
the database allows you to produce plots for a complete
survey, using user defined parameters for both plot
components and number of soundings per page. A newly
introduced GROUP ID can also be used to group soundings
for plotting.
TEMIX also features the smooth
model inversion that utilizes constant thickness layers
to approximate a quasicontinuous model; only the
resistivity are used as parameters in the inversion.
The binary data base format enables
up to 200 soundings to be stored in a single,
variablesize data base file. You can view and plot the
survey field geometry.
Interactive model input via the
mouse allows the user to see changes in the calculated
curve as he enters or changes the model (times are
automatically converted to depths).
TEMIX XL v4
TEMIX XL contains all the features
of TEMIX but with additional facilities for creating
maps and profiles from the data. Map Functions
A newly introduced MAP category
allows the user to display the location map of the
survey with icons representing the soundings as well as
a data window and a model window. Individual soundings
can be selected for interpretation from the displayed
map using the mouse or cursor keys. Model copy and paste
commands allow for fast and easy starting model
generation.
The map can be contoured with the
apparent resistivity at any time, the resistivity at any
depth or elevation, or of any layer. Thickness,
elevation or depth of any layer can also be contoured.
Conductivity can be substituted for resistivity in every
case.
Profile Functions
Profiles can be selected from the
map display by drawing a polygon around the desired
points with a mouse. A bestfit profile line is
generated and the soundings are projected onto the
profile line. A second new interactive display shows the
selected profile, selected sounding curve, synthetic
data, and the smooth and layered models. The profile
display can be selected from a wide variety of data and
interpreted model parameters, from layered
crosssections to profile plots to contoured
pseudosection.
Profile plots can be in contoured
section or pseudosection form. Vertical axis can be
elevation or depth for sections. Model cross section is
also available. Resistivity, conductivity or voltage can
be displayed.
Both contour map data values and
profile section and pseudosection values can be exported
in Geosoft XYZ format for import into more sophisticated
contouring or 3D display software.
Display Options
Final results for multiple sounding
interpretations can be presented in "PLATE" style
format. These can include the map (with profiles and
contours), along with data and model displays for the
selected profile. There are many options available for
the model section and data displays.
Vertical axes for data and model
can be linear or logarithmic. Data can be presented as
profiles, as a pseudosection or as a sequence of
laterally displaced sounding curves ("Zaborovsky" plot).
Models can be presented as layered
model sections or contoured sections of layered or
smooth models, with either depth or elevation as the
vertical axis. Smooth and/or layered models can be drawn
beneath each station in "well log" form.
In addition to the above, location
maps can be produced with user definable "icon" plots of
the sounding data and models at the correct location on
the plan view. Tools are provided to move "icons" of
plots to new locations if they overlap.
Standard Components
TEMIX or TEMIX XL software and
instruction manual.
