Sustained Changes in Well Water Levels Following a Large Earthquake: Possible Evidence of Permeability Decreases in a Shallow Groundwater System

Abstract

• Sustained changes occurred in well water levels in the Canterbury Plain after the Darfield earthquake • These sustained changes suggest widespread permeability decreases in the shallow groundwater system • These permeability decreases could be attributed to the consolidation of sediment in the Canterbury Plain

Far‐Field Groundwater Response to the Lamb Waves From the 2022 Hunga‐Tonga Volcano Eruption

“…Nevertheless, a detailed mechanism is needed to explain how the globally propagating plane wave‐mode, Lamb waves, induce groundwater level responses. Unlike the co‐seismic response of WL (Liao et al., 2021; Shi & Wang, 2016; Weingarten & Ge, 2014), the Lamb wave has a significant propagation direction and affects groundwater from surface. Hence, we suggest that current model needs to be slightly modified so that it can be used to better describe the WL response to long‐distance propagating perturbations such as Lamb waves.…”

Groundwater Hydraulics in Increased Spring Discharge following Earthquakes: Some Applications and Considerations

“…This spring is located in the Iberian Mountain Range (Spain) and drains a large limestone aquifer over 1500 m thick with significant confinement. Its hydrodynamic volume at the average initial date of the depletion curves has been estimated as 25 hm 3 , with a flow rate of 870 L/s. Its hydrograph was simulated for 20 years using the SIMERO model [23,25,27], and presents an analysis of the effects on its flow from a possible artificial recharge made at the center of gravity of its aquifer.…”

“…where Q 0 = 500 L/s (0.5 m 3 /s) and Q t = 100 L/s (0.1 m 3 /s), resulting in t = 487 days. The volume evacuated during this period would be 8.4 hm 3 .…”

“…However, post-earthquake increases in water levels in wells are not universal phenomena. There may also be prolonged drops in water levels [3,4].…”

“…The ultimate origin of these phenomena involves various mechanisms related to static and dynamic stresses [6,7], permeability changes [3,[7][8][9][10][11], and sediment consolidation [9,[11][12][13]. However, common hydraulic explanations draw on the ease or sensitivity of an aquifer to the increase in piezometric or hydraulic head potential due to the earthquake, manifesting in the rise in groundwater levels (groundwater level changes).…”