A new groundwater observation well constructed on the Suzuka-toen fault zone- the Hokusei well.

摘要

A new observation well, the Hokusei well, wasconstructed on the Suzuka-toen fault zone for earthquakeprediction and monitoring the activity of faults. As for thegeology at the Hokusei well, a syncline of the Quaternaryformation is reported in addition to an active fault, theFumotomura fault. To monitor two kinds of groundwatercontained in such geologic structures, syncline and active fault,the Hokusei well have double casing pipes that are arrangedconcentrically. The depth of the wells are 290 m and 500 m ofthe outer and inner pipes, respectively. In the inner pipe, there isa sequence of the screen near the axis of the syncline. In theouter pipe, there are three sequences of the screens near the Fumotomura fault.The depth of the Fumotomura fault at the point of the well isassumed to be 170 - 190 m based on the core sampleobservation. The groundwater obtained from the fault deptb ischaracterized to be rich in Si and Fe. The transmissivities of allaquifers are estimated to be about 10~(-6) m~2/s by pumping tests.