The nonlinear finite element code DYNAZ was utilized to estimate the earthquake response of two liquid storage tanks of different aspect ratios: a broad tank and a tall tank. The broad tank is 40 ft high and has a radius of 60 ft. The shell thickness is assumed constant of 1 inch and the base plate is considered having 1 inch of uniform thickness. The tall tank is 72 ft of high, 24 ft in radius, and has both shell and base thickness of 1 inch. Both tanks are assumed full of water to capacity. Each of the two tanks were subjected to two different earthquake motions: the East-West component of the 1940 El Centro earthquake which has a peak ground acceleration of 0.214 g, as shown in Figure (5.1), and the record from the Northridge earthquake measured at the Arleta site which has a peak ground acceleration of 0.344 g, as shown in Figure (5.2), and measured in a direction of 90 from the hypocenter direction. The responses of the two tanks were estimated assuming different boundary conditions: rigid tank walls, flexible tank walls completely anchored and flexible unanchored tank walls.