Final answer:
Soft ground tends to amplify seismic forces because it is less rigid, allowing P-waves and S-waves to have larger amplitudes, leading to greater ground displacements and potentially more damage.
Step-by-step explanation:
Seismic forces can be amplified by the type of ground they travel through. When an earthquake occurs, it generates waves with both longitudinal and transverse components, known as P-waves and S-waves, respectively. These waves propagate through the Earth's crust at varying speeds, depending on the rigidity of the medium. In more rigid materials like granite, both P-waves and S-waves travel at faster speeds. In contrast, sediments, being less rigid, can slow down these seismic waves. Such slower speeds in soft ground can lead to larger amplitudes of seismic waves, which can then result in more significant ground displacements and potentially amplify the damage caused.
Furthermore, the energy in a wave is directly proportional to its amplitude squared. This means that as earthquake waves with a larger amplitude travel through soft ground, which does not dampen the waves as effectively as hard ground, the seismic energy may be amplified, resulting in more substantial shaking and potential destruction.