Electrical Tomography Software Res3dinv0 pages

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DATA INVERSION SOFTWARE FOR □Slfxl

ELECTRICAL IMAGING AND INDUCED

IZATION (IP) RES3DINV

This software has been developped for the inversion of data

collected as to an electrode grid with rectangular meshes

(Loke & Barker, 1996). The spreadings being supported

include Pole-Pole, Pole-Dipole, line Dipole-Dipole, equatorial

Dipole-Dipole and Wenner-Schlumberger.

RES3DINV uses the minimum squares method to produce

a sub-soil 3D model starting from the data of apparent

resistivity. We warmly recommend to use a computer with

minimum the following features: microprocessor Pentium

II or IH\ 64Mb of RAM and hard disk of 6.4 Gb.

Further to the dimensions of the grid and the number of

acquisitions, the 3D inversion of a single set of data may

as a matter of fact require from a few minutes up to more

that 12 hours, depending on the performance of your PC.

The program automatically selects the best inversion

parameters for a certain set of data (those parameters may

anyway be modified by the user). Three different versions

of the minimum squares method are available for the

inversion: a fast 'almost-Newton* method, a slower and

more accurate 'Gauss-Newton* method, and finally a hybrid

technique, rather fast and accurate at the same time.

The 'smoothing* filter may be adjusted in two different ways:

the first way is optimized for those areas that are characterized

by a gradual variation of the resistivity with the depth, the

other way is optimized for areas with very clear-cut variations.

The topographical corrections may be entered using a

'distorted* grid of finished elements in order to coincide with

the topographical undulations (Sazaki 1994)

0.0

10

3D

Lernacken Sludge Dep

00 1 0 20 30 40 SO SO 70 80 90100 0.0

o.o

□ sit survey

10 20 30 40 SO BO 70 SO 90100

Layer 1 Depln: 0.00-3.50 m.

0.0 10 20 30 40 50 SO 70 SO

0.0

Layer 2 Depth : 3.50-7.53 m.

10 20 30 40 SO BO 70 SO 90100

Layer 3 Oeplh : t 53 12.2 m.

0.0 10 20 3D 4D 50 60 70 80 90100

DO

Layer 4 Depth 12.2-17.S m.

10 20 30 40 SO 00 70 80 90100

Layers Depot 117 5-23.6 m

X Unit Electrode Spacing S.OM, V Unit Bei

116 tall on G - RMS Error B.T<H>

Layer B Depth ; 23 8-30 6 m.

e Spacing 5.0M.

2.0 4.0 0.0 16.0 32.0 64.0

Resistivity In Oh mm

Time tsken(200 MHz Pentium Prol t5162»eis.

120

256

3D model : restitution with horizontal sections ('horizontal slice*) at different depths

(Dahlin, T and Bernstone, C, 1997, A roll-along technique for 3D resistivity data acquisition with

multielectrode arrays, Procs.SAGEEP'97, Reno, Nevada, Vol.2,927-935)

3D vision of a gold and copper deposit

(combination of data for apparent

resistivity+IP) (Courtesy of Arctan service

Pfy.Ltd., Australia and Phelps Dodge Corp.,

USA)

Porphyry copper gold prospect in Southeast Asia

IP>20mV/V IP>30mV/V Resist! vity>1000 ohm.m

I Courtesy of Arctan Services Pty. Ltd. (Australia) and Phelps Dodge Corp. (USA)

www.pasigeophysics.com