【實用工具app】ERTdesign|最夯免費app

ERTdesign is a geophysical app that estimates the depth of investigation for Electrical Resistivity quadrupoles with in-line electrodes (VES or 2D ERT measurements). The tool also calculates the geometric factor of the quadrupole and provides an estimate of the expected Vmn signal at the receiver.

The following electrode arrays are parsed:

- Wenner;

- Wenner-Schlumberger;

- Dipole-dipole;

- Pole-dipole;

- Pole-Pole;

- Gradient Array;

- Generic quadrupole: just define the coordinates of the four A, B, M and N electrodes.

This last feature is useful when estimating the real depth of investigation for arrays making use of remote poles not really at "infinite" distance from the set.

The depth of investigation estimate is performed, first, integrating the analytic sensitivity function - for the given quadrupole - and then by calculating the "median z depth", so that the area under the sensitivity curve is equal to the 50% of the total area (Edwards, 1977; Baker, 1991).

Processing steps:

1. Select array type (Wenner, dipole-dipole,...) and display the geometry for the A, B, M and N electrodes.

2. Set the quadrupole configuration: lenght of the receiving /transmitting dipole and TX-RX distance (levels), or, for a generic array, set the coordinates of the A, B, M and N electrodes.

3. Set the field parameters for estimating the expected Vmn signal: average background resistivity (ohm m) and injected current (mA).

4. Calculate depth of investigation, geometrical factor and Vmn signal.

References

Barker, R.D., 1991. Depth of investigation of collinear symmetrical four-electrode arrays. Geophysics, 54, 1031-1037.

L.S. Edwards, 1977. A modified pseudosection for resistivity and induced-polarization. Geophysics, 42, 1020-1036.

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