Solution of problem on SIP (Shear-induced Polarization) in fault gouges and the development to the field observations.

对断层泥材料剪切变形过程中产生的电势进行了实验研究。在室内剪切变形试验中，在粘土等普通饱和细集料中可以观察到一些电极化现象。这种现象被称为SIP（剪切诱导极化）。这种SIP现象可以用细颗粒与间隙水与电解质之间的物理化学相互作用来解释。而用非偶极子油处理的手工业用重塑粘土中未检测到SIP。通过平面剪切应变试验，明确了感应电位极性与变形和应变感的关系。最大应变轴（张）平面上产生的电荷符号为正，最小应变轴平面上产生的电荷符号为负，中间应变轴平面上产生的电荷符号为中性。另外一种变形试验也证实了泥样的这一特性。通过测量滑坡的自发电位，对滑坡部位进行了SIP观测。场地位于日本东北部新泻县八越市Busuno滑坡区和日本四国高知县长冈市Nuta Yone滑坡区等大型滑坡区。随着滑坡位移的增大，自然电位发生变化。在滑坡块体边界处观察到较大的电位分布不连续。在滑坡场观测到的电势感觉与室内模型实验得到的感觉一致。

An experimental study on the electrical potential induced in fault gouge materials accompanying with their shear deformation have been carried out. Some electrical polarizations could be observed in common saturated fine aggregates, such as clay during the shear deformation test in laboratory. This phenomenon is called SIP (Shear-induced Polarization). This phenomenon of SIP can be interpreted in terms of physicochemical interaction between fine particle and interstitial water with electrolyte. However, the SIP was not detected in the remolded clay for handicraft-use which treated with some non-dipole oil.The plane shear strain test was performed to clarify the relation of the polarity of induced potential with deformation and the sense of strain. Sign of electric charge generated on the plane of maximum strain axis (tensional) was plus, that on the plane of minimum strain axis was minus and that on the plane of intermediate strain axis was neutral. This characteristic property was confirmed in gouge sample by the other kind of deformation test.We observed SIP at sites of landslide by measurement of the spontaneous potential. The sites locate at large scale of landslide areas of Busuno landslide area in Jouetsu City, Niigata Prefecture, Northeast Japan and Nuta Yone landslide area in Nagaoka, Kochi Prefecture, Shikoku, Japan. The spontaneous potential changes with increasing the displacement of landslide. The large discontinuity of the electric potential distribution was observed at the boundary of landslide blocks. The senses of electric potential observed at landslide fields coincided with those senses obtained from the model experiments in the laboratory.