A new hypothesis, termed hydroseismicity, suggests that in crustal volumes with fracture permeability, natural increases in hydraulic head caused by transient increases in the elevation of the water table in recharge areas of groundwater basins can be transmitted to depths of 10–20 km and thereby trigger earthquakes. The flow-path geometry resembles, except for scale, the model familiar to groundwater hydrologists for near-surface flow. Possible trigger mechanisms for hydroseismicity include small increases in fluid pressure at hypocentral depths caused by such transient increases, the dissolution of minerals in water, and the solubility of water in minerals (hydrolytic weakening) that leads to structural weakening. A change in water level of less than 1 m (<0.1 bar) is sufficient, in principle, to trigger seismicity along a preexisting fault in a crust already tectonically stressed close to failure. Flow lines in the hydroseismicity model are over distances of tens of kilometres. Implicit in the model is a primarily diffuse distribution of epicenters (as is observed in the region) rather than concentrations along discrete geologic (faults) or geomorphic (rivers) elements.