Today's topics Mechanisms of earthquakes. Fault motions and elastic rebound theory. A structure which straddles a fault rupture will almost surely be destroyed, but that probablity is very low. The ground shaking induced by fault rupture causes much more widespread damage. The nature of shaking at a particular site depends on many factors concerning the nature and distance of the origin of the earthquake and the surrounding geology.
Waves propogate through the earth's crusts in several forms.
P waves and S waves are most prominent. In addition to fault rupture and ground shaking, shaking can also induce tidal waves, called tsunamis . Liquefaction Liquefaction occurs in loosely packed saturated sand when seismic shaking compacts the sand, resulting in increased pressure in the surrounding water. The pressure in the water can rise to the point where it carries all the stress in the soil, so the sand grains carry no net pressure and can flow past one another. Landslide Seismic shaking can induce landslides in unstable soil.