Optimized survey design: efficiently exploiting the full information content offered by geoelectrical data
Abstract
With the introduction of multi-electrode acquisition systems and 2D and 3D tomographic inversion codes, the geoelectrical method has experienced a renaissance and is currently the method of choice for many applications associated with hydrological problems. Despite the flexibility offered by the multi-electrode systems, the majority of applications reported in the literature continue to employ traditional electrode configurations such as the Wenner, Dipole-Dipole or Schlumberger arrays. These arrays were designed for efficient data acquisition using four-electrode recording systems, and may thus be not optimal for constraining 2D or 3D tomographic models. By using tools provided by statistical experimental design, we have shown that the resolution power of geoelectrical data can be improved substantially by appropriately combining "arbitrary" injecting and measuring dipoles. An important conclusion from these studies was that optimal data sets comprise many more measurements than traditional data sets. To ensure efficient data acquisition, we have developed a novel multi-electrode array that allows parallel measurements to be made, such that electrical currents are injected through two electrodes and the remaining electrodes measure the potential differences simultaneously with respect to a reference electrode that can be chosen arbitrarily; for an n-element electrode array, n-3 measurements can be made simultaneously. Despite the parallel data acquisition capability, there still exist a large number of possible (parallelized) measurement configurations out of which optimal configurations need to be identified prior to an experiment. This number of configurations could be reduced substantially by only using pole-pole or pole-dipole configuration. Since pole-pole configurations are susceptible to high noise levels, we employ the more robust pole-dipole configurations. With only 2n parallel pole-dipole scans, any other pole-dipole configuration can be reconstructed with acceptable accuracy. This leads to highly efficient field procedures and facilitates application of post-acquisition experimental design procedures that result in the identification of those electrode configurations that constrain the tomographic models in an optimal fashion.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H42D..03M
- Keywords:
-
- 0694 Instruments and techniques