Abstract: This paper proposed a “circular method” of underground water precursor observation to achieve comprehensive static water level and hydrochemical observations in a single well. A circular system is introduced. The hydrochemical observation can be conducted at the top part of the circular system, which is located at the well entrance. Since the water level observation at the static-water-level-state can be achieved simulta neously, this method provides the base for single-well comprehensive observation for both the well water level and hydrochemistry. The principle of this method in the hydrochemical observation has been described quantitatively. The hydrochemical equilibrium equation has been deduced, which theoretically proves the efficiency of the circular method. Some experimental results are also introduced in the paper.

Key words: Earthquake, Underground water precursor, Single-well comprehensive observation, Circular method