ACF-4M DATA PROCESSING AND INTERPRETATION SOFTWARE TOOLS

– the control and data processing program SM27
– the robust data processing program SM+
– the data archiving and visualization program Geoinf32
– the 1D inversion program MEL
– the 2D inversion program Shell2d

THE SM27 PROGRAM

The SM27 program is intended for equipment ACF-4M operation control and data processing with apparent resistivity and impedance phase curves obtaining. Output data formats are *.sbf, *.laf and *.txt. Data of the SM27 program can be used in the Geoinf32, MEL and Shell2d programs, and also in the WinGLink software package.

The SM27 program fulfills initial testing and control of the equipment operation, setting of equipment parameters (numbers of magnetic coils, lengths of electric lines, azimuths of magnetic and electric sensors, etc), setting of measurement’s parameters (duration, frequency range, recurrence), application of magnetic coils, preamplifier of electric channels and recorder calibrations, connection the recorder to PC, viewing and estimation of data quality (time series, auto- and cross spectra of signals, dynamic spectra, apparent resistivity and impedance phase curves). In favorable conditions (low noise level, low grounding resistance) the obtained curves can be used for inversion.

THE SM+ PROGRAM

The SM+ program is intended for the robust data processing and analysis, obtaining smoothed curves of apparent resistivity and impedance phase and data export to inversion software tools. The program provides the calibrations application, data transformation from linear to logarithmical scales with choice of amount of points for one decade, application of impedance or admittance estimations of apparent resistivity, using various methods of data processing at receiving of AMT curves, looking through data in the graphic view, storing the processed data in .txt, *.laf and *.edi formats for the second stage of data processing and interpretation using programs Geoinf32, MEL и Shell2d. Output files of the SM+/AMT program can be used in 1D and 2D inversion programs of the WinGLink package.

The SM+ program includes several modules. The first one is used for the time series data processing, auto and cross spectra of electric and magnetic field signals calculation and for obtaining of the apparent resistivity and impedance curves with use various robust and noises filtration technologies. This module also allows users to process AMT data obtained by remote reference technology. The wide graphical range of this module, such as dynamic values distributions, selector weights, frequency distribution of ellipticity parameters and others, allows user to study features of EM field components and to estimate the reliability of spectral selectors of the program applications. The file containing the of apparent resistivity and impedance phase estimations for the receiving array directions, principal directions and fixed azimuths, and also values of auto and cross spectra for all channels is a result of this module operation. The second module is applied for coordinates setting and the data type selection which will be used at the following stages. The third module is used for viewing, manual correction and smoothing of apparent resistivity and impedance phase curves. This module allows user to apply corrections for calculated sounding curves at the non-zero grounding resistance.

THE GEOINF32 PROGRAM

This program is intended for AMT data archiving, visualization and analysis along a profile or on an area and also for data export to inversion software tools. Geoinf32 program allows a user to derive a coordinate plane with sounding stations, to view sounding curves for each station, to plot of apparent resistivity and impedance phase values for selected frequency ranges, to derive pseudo sections of the selected parameter along a profile, to plot polar diagrams on the coordinate plane, distribution of such parameters as apparent resistivity, impedance phase, parameters of heterogeneity on the coordinate plane for selected frequency ranges, to exclude bad sounding stations, to export AMT data to inversion software tools and Grapher/Surfer programs. The program forms files for 1D (MEL) and 2D (Shell2d) inversion software.

THE MEL PROGRAM

This program is applied for 1D inversion of AMT data based on the use of the Method of Effective Linearization (MEL), and for AMT data modeling for horizontal layered medium. The program does not require the medium model setting (layered for example) for inversion. It calculates cross sections at the minimum discrepancy of calculated curves of apparent resistivity and impedance phase and field curves. The dependence of resistivity from depth for each station is the result of the calculation. The resolution of calculated section depends on number of points in source data.

THE SHELL 2D PROGRAM

The Shell 2d program is applied for direct and inverse problem of AMT sounding solution in two dimensional (2D) medium model. The inversion based on use of integral equation method according to modified OCCAM algorithm. The graphical interface allows user to control the inversion results, to change parameters, to estimate the approximation reliability and stability of inverse problem solution.