A rectangular tank of 30 ft. width and 15 ft. liquid height is subjected to the East West component of the El Centro earthquake record measured at the Imperial Valley site. The peak ground acceleration of this record is 0.21g. In order to filter high frequency surface wave components that propagate along the free surface, a dissipation factor of 0.025 is used. A finite element mesh that consists of 9-noded isoparametric liquid elements with a total of 441 nodes is used. Results are obtained and compared to those obtained from Ref. . In order to show the free vibration response of the free surface, the time histories were obtained till time t=80 sec. although the earthquake duration was 53.48 sec. Figures (4.20) and (4.21) show wave height time history along the tank left and right wall, respectively.