A unifying mechanism for hydrological responses to earthquakes

Liquefaction - the worst natural hazard to engineered structures - has long been attributed to undrained consolidation of sediments under earthquake loading. Here I show that recent field evidence supports instead a model that liquefaction of the near-surface sediments may be mostly due to the diffusion of elevated pore pressure from a lower, confined aquifer in response to an earthquake-enhanced vertical permeability. Undrained consolidation may cause liquefaction only at distances much closer than one ruptured fault length from the hypocenter. The model explains a suite of observations and provides a unifying mechanism for a broad spectrum of hydrologic responses to earthquakes. It may also facilitate the evaluation of the liquefaction potential of a site.