Vertical Leakage Occurred after an Earthquake: Suggestions for Utilizing the Mixed Flow Model

Abstract

Abstract Permeability is an important parameter of shallow crust that affects underground water migration. It is important to calculate the permeability changes caused by earthquakes for underground engineering safety and pollutant dispersion. The response analysis of groundwater in wells, to Earth tides, has been widely used to calculate permeability. However, the calculation results and the judgment of leakage are controversial. In this study, the water level response of both the M2 and O1 tidal waves in the Zuojiazhuang well was analyzed. An optimization fitting, using the mixed flow model, was performed to calculate the hydraulic parameters of aquifers and aquitards. After the Wenchuan earthquake, the horizontal transmissivity of aquifers increased temporarily and then slowly recovered. However, after the Tohoku earthquake, the horizontal transmissivity increased permanently by one order of magnitude. The vertical hydraulic conductivity increased permanently by three orders of magnitude, meaning that vertical leakage occurred. As both the M2 and the O1 waves are used as constraints for the calculation with the mixed flow model, the results of this study are more precise than those of previous ones. This article also gives some suggestions for utilizing the mixed flow model.