Abstract: Through studying the observed data of water level, well-head pressure and outflow in Wuhe and Lujiang wells, Anhui Province, China, the authors found the precursory evidences of the far-field. Before Philippine earthquake ( M=8.0, July 16, 1990), the amplitude ratio (a) and phase difference (Δθ) of M₂ wave of water level in Wuhe well (Δ=2033 km) showed anomalous low values for 17 months and the well-head pressure and outflow in Lujiang artesian well (Δ=1860 km ) showed anom alous low values for 36 months before the event. Before the Taiwan strait earthquake ( M =7.3, Sept. 16, 1994), the a and DJin Wuhe well (Δ=1121 km ) showed low values for 35~36 months while the well-head pressure and outflow in Lujiang well (Δ930 km) showed anomalous low values for 35~36 months. At the occurrence time of the earthquakes, the anomalies returned, rebounded and changed coseismically. After the earthquakes, all anomalies keep in high values and normal annual variation. From December 1986 to June 1997, the isomorphic, synchronous and coseismic anomalous variations of the observed data occurred only before these two strong earthquakes. The evidence may indicate that there are the far-field medium-long term anomalies for some strong earthquakes.

Key words: Large earthquake, Ground fluid, Medium term precursor, Far-field