Why does the soil become fluid after some earthquakes?

The reason for this situation, which is observed after some earthquakes and leads to increased damage caused by the earthquake, is the liquefaction that causes the soil to turn into a muddy structure. Liquefaction is generally about 10-20 meters below ground, structures that are weakly connected to each other and have water in the spaces between them to act like a liquid due to earthquakes. The reason why this situation does not occur after each earthquake is related to the fact that there is a large amount of water in the voids in the structure of the granular materials that make up the soil. For example, earthquakes occurring in areas with hard rocks such as granite on the ground do not cause liquefaction of the soil. However, the grounds of regions formed by the accumulation of materials (eg sand) carried by streams are never strong enough. Because in granular structures such as sand, the particles are stacked on each other and are not tightly connected to each other. The earthquake causes these particles to get close to each other and squeeze, resulting in increased pressure of the water between the particles. When the pressure of the water is high enough to move the sand particles, the ground becomes liquefied and becomes muddy.