Study on the Piezomagnetism and Streaming Potential Based on the Local Geomagnetic and Geoelectric Variation Observed on the Shore of the Man-Made Lake Under the Seasonal Control of the Water Level

在杉泽水坝湖的海岸及其附近进行了地磁场和地电场的连续测量。尼基南科湖。测量的目的是（1）通过压磁检测由湖水负荷引起的局部地磁场和（2）利用流动电位现象，在湖底或周边可能存在渗漏水的情况下，探测由湖水压力引起的局部地电场。在湖的海岸连续测量了一年左右后，我们计划从1989年8月开始测量到1991年底。结果表明，当地地磁场的变化与坝湖水位的变化是一致的。地磁总强度随水位的升高而降低，压磁系数为-0.014。DM 1时为-0.013和-0.065（nT/m）。DM 2和DM 3。分别它们与Davis和斯泰西（1972）得到的结果一致。Abudullabekov等（1979）和Brennan和Hastie（1979）.至于电极间地电位差的时间变化与湖泊水位变化的关系。电位差的增加。EP（1-0）和EP（2-0）似乎是随着水位的升高而同时发生的。除此之外，我们还成功地观测到了距日南湖约4公里处的5.3级地震前地电位差EP（1-2）和EP（2-0）的一次短暂变化。

Continuous measurement of the geomagnetic and geoelectric field were carried out on the shore and its vicinity of the Sugesawa-dam Lake. Lake Nichinanko. which is located in the western part of Tottori Pref.Objectives of the measurement are (1) to detect the local geomagnetic field caused by the load of the lake water through the piezomagnetism and (2) to detect the local geoelectric field caused by the lake water pressure in the circumstance of the probable existence of the leakage of water from the bottom or surrounding of the lake through the streaming potential phenomenon.Continuous measurement started in the August of 1989 and we are now planning to continue until the end of 1991.After the continuous measurement of about one year on the shore of the lake. We found the local geomagnetic change is concordant with the change of the water level of the dam lake. Decrease of the geomagnetic total intensity occurs simultaneously with the increase of the water level.Piezomagnetic coefficient thus obtained are -0.014. -0.013 and -0.065 (nT/m) at DM1. DM2 and DM3. respectively. And they are concordant with the values obtained by Davis and Stacy (1972). Abudullabekov et al (1979) and Brennan and Hastie (1979).As for the relationship between the time variation of the geoelectric potential difference between electrodes and the change of the water level of the lake. the increase of the potential difference. EP (1-0) and EP (2-0) seems to have occured simultaneously with the increase of the water level of thlake. However, we cannot get conclusion at this moment because of the fairly long interruption of the observation in the year of 1990.In addition to these, we succeeded to observe a precursory change of the geoelectric potential differences EP (1-2) and EP (2-0) preceding the earthquake of M=5.3 which occured at about 4 kilometers distance from Nichinanko Lake.