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Res2Dinv - 2D Resistivity & IP Inversion Software
Two-dimensional (2D) electrical imaging surveys are now widely used to map areas of moderate- ly complex geology where conventional ID resistivity sounding surveys are inadequate. The RES2DINV program uses the smoothness-constrained least-squares method inversion technique (Sasaki 1992) to produce a 2D model of the subsurface from the apparent resistivity data. It is completely automatic and the user does not even have to supply a starting model. On a Pentium based microcomputer, the inversion of a single pseudosection is usually completed within minutes. It supports the Wenner, Schlumberger, pole-pole, pole-dipole, inline and equatorial di- pole-dipole, gradient and non-conventional arrays.
Technical Specifications
The program will automatically choose the optimum inversion parameters for a data set. Howev- er, the inversion parameters can be modified by the user. Three different variations of the least- squares method are provided; a very fast quasi-Newton method, a slower but more accurate Gauss-Newton method, and a moderately fast and accurate hybrid technique. The smoothing fil- ter can be adjusted to emphasize resistivity variations in the vertical or horizontal directions. It can also be optimized to produce models with smooth boundaries (for e.g.. chemical plumes), or with sharp boundaries (for e.g.. fracture zones). Resistivity information from borehole and other sources can also be included to constrain the inversion process. Three different techniques for topographic modelling (Loke 2000) are available in this programme.
The second example is from a combined resistivity and IP survey over the Magusi River massive sulphide ore body (Edwards 1977). This survey was conducted with 30.5 meters, 61.0 meters and 91.4 meters dipoles. The re- sulting pseudosection has a very complex distribution of the data points with overlapping data levels measured with different dipole spacings. The apparent re- sistivity and IP pseudosections, together with the model sections obtained are shown in Figure The ore body shows up as a dis- tinct low resistivity body with high IP values near the middle of the survey line in the model sections. Note the sharp boundaries be- tween ore body and the sur- rounding rocks
Supports on land, underwater and cross-borehole surveys
Supports smooth and sharp contrasts inversions
Supports exact and approximate least-squares optimization methods
Supports up to 16000 electrodes with almost any electrode arrangement
Fast seamless inversion of very long survey lines using sparse inversion techniques