Obtaining Aquifer Parameter By Earth Tidal Effect

Many studies have shown that earthquakes can affect the well-aquifer systemparameters, such as hydraulic conductivity, storage coefficient, porosity, etc. Theprevious research reveals that the solid tide can influence groundwater level andgenerally there exist a phase lag, and we can obtain aquifer parameters by tidal effectsinversion.In this essay, on the basis of previous study, writer tried to analyze the inversionof hydrogeological parameters of the region through the extraction of earth tidal effectof well-water level, and compared the results were calculated before and after theearthquake. We have water level observation of Dingjiaping, Maoping and Guojiabawells of Sanxia well network, make three wells data analysis and processing, toextract the tidal signal in the observational data, then use the EIS2000and Baytap-Gseparately calculated phase lag and tidal factor. On this basis, further storagecoefficient and hydraulic conductivity is obtained. By comparing the aquiferparameters obtained before and after the earthquake, and observing the link betweenthe coseismic water level curve and parameters, we can get the following conclusions:Storage coefficient of the three wells reduced in varied degrees after theearthquake. Storage coefficient of Guojiaba well grew larger slowly before theearthquake, and then it reduced quickly after the earthquake, with66%change beforeand after the earthquake, which was the biggest in three wells. When the earthquakeoccurs, the hydraulic conductivity of the three wells increases, but it decreases afterthe earthquake. The hydraulic conductivity changes before and after the earthquake.When the earthquake occurs, the change in hydraulic conductivity in Dingjiaping isabout four times, and then gradually reduced and maintained at1.2m2/d. Maoping isincreased before the earthquake by about2/3, and in a month back to the level beforethe earthquake. Guojiaba is5-6times bigger than that before the earthquake, after onemonth the hydraulic conductivity is about2times bigger than that before theearthquake, the recovery has been relatively slow. As that can be observed when the earthquake occurs, the direction of change ofhydraulic conductivity and storage coefficient is opposite, and the change of hydraulicconductivity is larger than storage rate, storage rate is relatively stable. From thechange of aquifer parameters, the more obvious the change of hydraulic conductivitywell-aquifer system, more obvious the coseismic water level changes, and the waterlevel recovery time is relatively short. The aquifer parameter change is an importantreason of this three wells coseismic water level change.The phase lag of Dingjiaping is positive, on which the mechanism requiresfurther study. We need pay more attention to the non-solid information such as therainfall, pumping, etc.