Mechanism of water level changes during earthquakes: Near field versus intermediate field

Abstract

Using a new empirical relation among earthquake magnitude, seismic energy density and hypocentral distance, we show that the documented water level changes during earthquakes occur across seven orders of magnitude of seismic energy density. Combining this relation with a global data set for water level changes, new data from Taiwan, and laboratory data for saturated sediments under cyclic loading, we show that at least two mechanisms may be important for inducing water level changes. Undrained volumetric change may be the dominant mechanism to cause the abrupt decrease or increase of water level documented in the near field, while an earthquake‐enhanced permeability may account for the more gradual and sustained water level changes documented in the intermediate field.