Vibration convection and fossil movement
The bone located in the middle of the container, which simulates the centre of a seismic zone, will experience the greatest vertical displacement.
Vibration convection occurs when granulated material like soil is subjected to seismic tremors or vibrations under the gravitational field. This causes the finer grains in soil to move downwards, while larger particles end up on top.
When a container of soil accelerates upwards due to seismic activity, its base lifts the entire mass of soil upwards. However, when the container falls back downwards due to gravity, friction between the sides of the container and the soil will also pull the soil down with the container. In this case, the soil nearer the sides of the container will fall more quickly than the soil in the middle of the container, causing the latter to appear to be raised.
Vibrations will also cause the lateral movement of grains in soil. This movement will cause collisions to occur between neighboring granules, which will then liquefy the soil. In turn, the soil will start moving and gain velocity.