Underwater earthquakes, submarine volcanic eruptions or landslides can cause tsunami. As it approaches a shallow coastline, its speed is reduced, but the height of the tsunami increases drastically, causing devastation on land. Thick sequences of unconsolidated sediments, such as sand, mud, and artificial fill, greatly magnify ground shaking during an earthquake. Ground shaking transmits forces to building that most buildings are not designed and constructed to endure. Ground shaking results in extensive property damage.
Bedrock is less likely to be affected by ground shaking than is unconsolidated material.
Buildings constructed on bedrock sustain far less damage than those built on unconsolidated material. Other dangers also come from the ground during an earthquake. Buildings constructed on sandy soil prone to water saturation have the greatest potential for complete destruction, because water-saturated sandy soil is subject to a phenomena called liquefaction. During liquefaction, water-saturated soil behaves as a fluid rather than as a solid. It becomes incapable of supporting much weight.