RESPONSE OF GROUNDWATER WELLS IN ALASKA TO NEAR AND DISTANT LARGE EARTHQUAKES

Transient water level changes due to large near and distant earthquakes are a common phenomena. In this paper we show a group of ground water wells near Fairbanks Alaska that responded by changing their water levels after the near by Nenana Mountain and Denali earthquakes and the distant Sumatra-Andaman earthquake. The transient water level changes after each earthquake had duration greater than the time of passage of the seismic waves from the respective earthquakes. This response cannot be explained by poroelastic theory. We used a diffusion equation to determine the source of pore pressure responsible for the changes in water levels for each well for each of the three earthquakes. From the result we infer that the water level changes could be due to the development of near by fracture (or by fracture cleaning) caused by ground shaking. Similar hypothesis have been proposed for the transient water level changes in other wells from different parts of the world.