Impacts of hydrogeological characteristics on groundwater-level changes induced by earthquakes

Liu, Ching-Yi; Chia, Yeeping; Chuang, Po-Yu; Chiu, Yung-Chia; Tseng, Tai-Lin

Impacts of hydrogeological characteristics on groundwater-level changes induced by earthquakes | Incidences des caractéristiques hydrogéologiques sur les changements du niveau des eaux souterraines induits par des séismes Impactos de las características hidrogeológicas en los cambios del nivel de agua subterránea inducidos por los terremotos 水文地质特征对地震引發之地下水位变化的影响 Impactos das características hidrogeológicas na variação do nível potenciométrico induzida por terremotos

2018

Liu, Ching-Yi | Chia, Yeeping | Chuang, Po-Yu | Chiu, Yung-Chia | Tseng, Tai-Lin

Changes in groundwater level during earthquakes have been reported worldwide. In this study, field observations of co-seismic groundwater-level changes in wells under different aquifer conditions and sampling intervals due to near-field earthquake events in Taiwan are presented. Sustained changes, usually observed immediately after earthquakes, are found in the confined aquifer. Oscillatory changes due to the dynamic strain triggered by passing earthquake waves can only be recorded by a high-frequency data logger. While co-seismic changes recover rapidly in an unconfined aquifer, they can sustain for months or longer in a confined aquifer. Three monitoring wells with long-term groundwater-level data were examined to understand the association of co-seismic changes with local hydrogeological conditions. The finite element software ABAQUS is used to simulate the pore-pressure changes induced by the displacements due to fault rupture. The calculated co-seismic change in pore pressure is related to the compressibility of the formation. The recovery rate of the change is rapid in the unconfined aquifer due to the hydrostatic condition at the water table, but slow in the confined aquifer due to the less permeable confining layer. Fracturing of the confining layer during earthquakes may enhance the dissipation of pore pressure and induce the discharge of the confined aquifer. The study results indicated that aquifer characteristics play an important role in determining groundwater-level changes during and after earthquakes.

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