ABSTRACT
We first acquire the resistivity of two sets of man-made samples using electrical resistivity tomography under different stresses and then construct their images of relative change. It was found that the resistivity-increased region expanded; meanwhile, the resistivity-decreased region shrank step by step with the increase of uniaxial stress in all of the resistivity images corresponding to the measuring lines placed at different directions (parallel to, perpendicular to, and intersecting the axis of load at 45°). These features are very similar to those prior to Tangshan ML 4.4 and 5.0 earthquakes that occurred on April 14, 1998, i.e. the similar trend changes in resistivity image that occurred during the preparation of the two earthquakes. This new finding encourages us to conclude that trend changes in resistivity image will be a potential, effective, and reliable indicator of an earthquake.
