Groundwater Level

Abstract

Groundwater level has long been known to respond to earthquakes; several types of response have been documented. Advances in the last decade were made largely through the studies of water-level response to Earth tides and barometric pressure. These studies have demonstrated that the hydraulic properties of groundwater systems are dynamic and change with time in response to disturbances such as earthquakes. This approach has been applied to estimate the permeability of several drilled active fault zones, to identify leakage from deep aquifers used for the storage of hazardous wastewater, and to reveal the potential importance of soil water and capillary tension in the unsaturated zone. Enhanced permeability is the most cited mechanism for the sustained changes of groundwater level in the intermediate and far fields, while undrained consolidation remains the most cited mechanism for the step-like coseismic changes in the near field. A new mechanism has emerged that suggests that coseismic release of pore water from unsaturated soils may also cause step-like increases of water level. Laboratory experiments show that both the undrained consolidation and the release of water from unsaturated zone may occur to explain the step-like water-level changes in the near field.