The most serious direct effect of earthquakes on buildings and structures is ground shaking. However earthquake shocks might pose other hazards in the form of soil liquefaction, which can result in considerable financial losses. Some soils such as quicksands and quickclays can give rise to major problems when disturbed by ground shaking. The ground vibrations produced by an earthquake lead to a decrease in the effective stress and in the shear strength of the soil which in turn trigger the liquefaction (Figure 1). Figure 1. Aerial view of leaning apartment houses in Niigata produced by soil liquefaction. Most of the damage was caused by cracking and unequal settlement of the ground such as is shown here. About 1/3 of the city subsided by as much as 2 meters as a result of sand...