## 3 Results and Discussion
### Stress and Acceleration  
Under earthquake activity, the acceleration and von Mises stress of the storage tanks in four different states exhibit different patterns. Maximum von Mises stress and acceleration values of tank wall are shown in Table 5. The maximum von Mises stress and shear force of the aboveground and underground tanks are located at the bottom of the tank wall, and the maximum acceleration is generally located near the dome at the upper part of the wall. Due to the influence of LNG, the structural acceleration of the full tank is smaller than that of the empty tank, and the acceleration of the aboveground tank is greater than that of the underground tank. Due to the load of soil, the stress of the underground tank is greater than that of the aboveground tank. The stress of the full underground tank is slightly smaller than that of the empty underground tank. The stress of the empty aboveground tank is the smallest. This indicates that soil pressure is the main load on the underground tank structure, which increases the compressive stress on the concrete wall and reduces tank acceleration. After storing full LNG in the underground tank, the liquid pressure can balance part of the soil pressure outside the tank, making the full tank safer than the empty tank. The results show that underground tanks have better safety performance than aboveground tanks under earthquake activity. Furthermore, the seismic response of the storage tank was evaluated under the influence of the EI-Centro seismic wave event (Southern California, 18 May 1940, with a magnitude of 6.9 and a peak ground acceleration of 3.41 m/s\({}^{2}\)). Comparative analysis with the Taft earthquake revealed that the EI-Centro event induced a significant escalation in the maximum von Mises stress, maximum acceleration, and relative deformation of the storage tank. Notably, the aboveground storage tanks exhibited a more pronounced increase in these parameters, suggesting a heightened susceptibility to seismic instability. To elucidate the influence of soil properties and geological conditions on the seismic response of storage tanks, we manipulated the soil's elastic modulus by increasing it by 50% and re-conducted the calculations. The augmentation of the soil's elastic modulus resulted in a decrease in the structural stress and deformation, thereby implying a mitigating effect on the structural response. Conversely, an increase in acceleration was observed, which suggests that soft soil conditions have the potential to amplify seismic responses. Hence, constructing underground storage tanks in hard soil enhances the structure's safety. The results indicate that underground tanks demonstrate superior safety performance under seismic activity compared to aboveground tanks, primarily due to the stabilizing support provided by the soil. The safety of underground tanks is further enhanced in the full state due to the balancing effect of the liquid pressure. However, the intensity of seismic \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Taft Wave**} & \multicolumn{2}{c}{**EI-Centro**} & \multicolumn{2}{c}{**Taft Wave (Harder Soil)**} \\ \cline{2-7}  & **[PERSON]** & **Max Acceleration** & **[PERSON]** & **Max Acceleration** & **[PERSON] Stress** & **Max Acceleration** \\  & **(MPa)** & **(m/s\({}^{2}\))** & **(m/s\({}^{2}\))** & **(m/s\({}^{2}\))** & **(MPa)** & **(m/s\({}^{2}\))** \\ \hline Underground full tank & 10.35 & 5.81 & 12.82 & 8.02 & 9.62 & 6.37 \\ Underground empty tank & 11.6 & 9.23 & & & & \\ Aboveground full tank & 8.42 & 6.17 & 11.36 & 8.63 & 7.87 & 7.05 \\ Aboveground empty tank & 5.35 & 10.04 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Maximum von Mises stress and acceleration values of tank wall. waves and soil conditions significantly affect the stress and acceleration experienced by the tanks, necessitating careful consideration of these factors in the design process.