Vibration convection and fossil movement
The hypothesis that the bone located in the middle of the container will have the most vertical displacement has not been proven to be true.
Vibrations caused by an earthquake causes grains in the soil to become compacted as water between the grains is expelled. The expelling of water, together with vibration, causes soil to behave like liquid. This process, which is known as liquefaction, creates landslides and undermines the foundations of buildings, causing them to collapse.
The science fair project may be modified to test which soil varieties are most susceptible to liquefaction, by using different types of soil, such as sand and clay.
The experiment may also be modified to test the displacement of materials of different density and sizes.
Convection - http://wapedia.mobi/en/Convection#7.
Facts about quicksand - http://www.dellamente.com/quicksand/doc/qsfacts.htm
Vibrations of granular material - http://thesis.library.caltech.edu/4504/