| By adopting unstructured triangular element that is easy to simulate ruggedterrain and inclined interface to subdivide mesh and grid automatic refinementtechnology, using dual weighted posteriori error estimation to guide mesh refiningprocess, we realized2.5D DC resistivity numerical modeling forward calculation bythe adaptive finite-element method.In the process of model analysis, we used our algorithm and software to calculatethe DC resistivity response of vertical dike model, which were compared with theanalytical solution of vertical dike model. The consequence showed that the numericalsolution for this algorithm has high accuracy，relative error of the numerical solutionis less than1percent except those points which are very close to the source point.After we confirmed the validity of the algorithm and calculating program, wecalculated2.5D geoelectric model apparent resistivity anomaly of undulatetopography and corrected the undulate topography by comparison method. Theconsequence of contrast between topographic correction results and level terrainresults shows that comparison method is effective to eliminate the terrain effect andgive prominence to the local geological anomalies.Then，we found that it is necessary to consider the impact of the undergroundanisotropic medium by comparing the DC resistivity response of isotropic medium toanisotropic medium. Anisotropy can better meet up with the actual geologicalconditions and explain geologic anomalies more exactly. Based on this consideration,we draw the apparent resistivity response curses and current density vector diagramswhen the underground medium is dipping anisotropic and the dipping angles aredifferent. The results showed that the current density mainly flows along the mediumwith low resistivity and its flowing direction is the direction of dipping undergroundmedium with low resistivity and the angle of the current density flowing direction isroughly equal to the dipping angle. |
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