The Study Of Self-potential Abnormity During The Rock Breaking

The study of self-potential(SP) had been researched as early as the 20th century. SP survey is a traditional geoelectric method, can sensitively reflect the variety of abnormal charges. This way is easy and exact, and the data is easy to deal with. Then under the allowable condition, this way is often adopted. A wealth of interesting case histories are reported in the literature concerning mining, hydrogeological, geothermal and archaeological surveying, as well as in engineering geophysics for landside and dam and embankment seepage control. In recent times there has also been a renewal of interest in the study of tectonic processes using the SP method, especially for forecasting earthquakes and volcanic eruptions. For example, some researchers in Greece and Japan have adopted the VAN way((Varotsos et al., 1993, Uyeda. 2000. 2002; Enomoto, 1997)). In many geoelectric stations of China, some SP experiments had been done to gain some experiences for inspecting earthquakes.In this paper, the author firstly reviewed the progress of SP study and emphatically studied the SP tomography, then found that the finished experiments lacked the systemic study in the time and the space. So the author participated in designing and doing a set of experiments, which was about the electrical variety during the rock breaking. The results of the experiments express that the electrical field change during the rock cracking. For deeply researching these phenomena, it is necessary to know the distribution of the abnormal charges. Then we induced The Patella theory. It is based on that the simple and quadratic field of the potential produced by point power can be expressed by the sum of the abnormal charges potentials in mathematic form. But in patella theory, the boundary condition is half-space. It does not apply to the limited boundary conditions. In fact not only to the experiment in laboratory but also to the work on field, the boundary influence could not be ignored. Then we should make progress in the SP tomograph)' to correctly find out the distribution and variety of the abnormal charges.In this paper, author developed Patella theory, and gave the theoretical result for the limited boundary, and based on the SP data, reconstructed the 2D abnormal charges occurrence probability tomography. The new model could adopt on Fl shape space, let this method reflect the distribution of the charges correctly under the limited boundary. From the result of experiments, the crack in the rock sample appeared on the same place as the max probability field of the positive charges. This fact could explain that there were some positive charges around the crack. The reason for the phenomena is possibly that when the rock was broken, the electrons fled from the tie of atoms, then the positive charges stayed in rock. Some charges which were not around the crack maybe make by the tiny crack in rock.In a word, in the paper, author expanded the applying range of SP tomography, made it convenient to experiment. Then from the result, we open out that the variety of accumulated charges was followed in the crack development, provided a powerfully useful tool for the study of earthquake auspice.