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Effect of outside anomaly in the cross-hole electrical resistivity tomography
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, EAGE-HAGI 1st Asia Pacific Meeting on Near Surface Geoscience and Engineering, Apr 2018, Volume 2018, p.1 - 5
Abstract
Cross-hole electrical resistivity tomography (CHERT) is very different from the Cross-hole travel time tomography since the measurement response is not only dependent on the properties between source and receiver. The anomalies outside the two boreholes will have unknown influence on the CHERT survey. In this study, the effects of outside anomaly were discussed from two aspects. First is the array cause that will lead to the symmetric effect in the inverted profile. The other is the extent of inversion region that will cause severely unexpected artifacts if not set up properly. This study aimed to use simple example to illustrate the correct application of CHERT method in engineering investigation. From the comparison of different electrode arrays and different inversion models, empirical countermeasures were proposed to obtain better CHERT results. The extended inversion model is recommended and the extended range on both side is suggested to be 1/2 of the borehole spacing. For the measurement configuration, at least two types of electrode arrays should be used in a CHERT survey, one without symmetric effect and the other with higher resolution. Hence, the combined data inversion or weight model stacking technique can be used to make better interpretation.