密云水库的构造磁实验

TECTONOMAGNETIC EXPERIMENT AROUND MIYUN RESERVOIR

为探讨水库地区的构造磁效应,在密云水库周围布设了2×21个测点,测点间距为2—5km,测点离水库堤岸的距离为几十米至15km不等,使用G-816型与G-826型质子旋进磁力仪,在1983—1987年期间,每季度观测一次地磁场总强度.地磁与密云水库蓄水的资料分析得到,地磁变化与水库的水位变化、水容量变化的关系系数分别为-(0.28±0.22)nT/m与-(0.35±0.31)×10^(-8)nT/m^3,表明地磁变化与该水库蓄水变化有着较强的负相关.这种较强的负相关可能是密云水库地区地下较强磁性岩石的压磁效应的反映.由于水库构造磁实验是地震磁现象的较好模拟,因此,根据实验结果可以相信,在地震活动区布设加密的高精度地磁观测,是能够捕捉到震磁前兆信息的。

To study the tectonomagnetic effect in the reservoir vicinity,2 X 21 sites,about 2-5 km apart,have been set up around the Miyun reservoir. The distances between geomagnetic sites and the reservoir bank are some tens of meters to 15 km. Using G-816 and G-826 magnetometers,geomagnetic total intensity was observed once each season during 1983-1987. Analysis of geomagnetic data and the data of water storage of the Miyun reservoir shows that the correlation coefficients between the geomagnetic changes and the variations in water level and water volume are - (0.28 + 0.22) nT/m and - (0.35 + 0.31) X 10-8nT/m3 respectively. It shows that there is a stronger negative correlation between the geomagnetic changes and the variations in the water storage. This rather strong negative correlation is probably a reflection of the piezomagnetic effect of the magnetic rock under the vicinity of the Miyun reservoir. Because according to the experimental results,the tectonomagnetic experiment around the reservoir is a rather good simulation of the seismomagnetic phenomena,it is believed that geomagnetic observations with a dense network in a seismically active area may catch the information of seismomagnetic precusors.