MEASUREMENT OF VERTICAL CONDUCTIVITY AND ITS APPLICATION IN RECOGNITION OF ABNORMAL WATER LEVEL IN SHUANGQIAO AND DONGTAIZI WELLS

In order to analyse the abnormal water level in saltwater well, we measured vertical conductivities for many times in wells of Shuangqiao No. 1, Shuangqiao No.2 and Dongtaizi which all lie near Tang-shan seismic region. Before Ninghe ML4.6 earthpuake on October 5, 1991 and Ninghe ML4.9 earthquake on July 22, 1992, the water conductivities in the wells, especially in aquifer position, showed high abnormal values. This is an effective and simple monitoring method for recognizing water level anomaliesinduced either by water pressure changes of saltwater layer or by the ingress of water from otherplaces.