A tsunami is a water wave or a series of waves generated by an impulsive vertical displacement of the surface of the ocean or other body of water by an earthquake or other cause. These waves can extend the damaging effects of an earthquake event thousands of kilometers from the earthquake focus. Ground failures accompanying earthquakes include landslides, liquefaction, lateral spreads, differential settlements, and ground cracks. Earthquake shaking often dislodges rock and debris on steep slopes, triggering rock falls, avalanches, and landslides. These slides have been known to bury entire towns and may be the most damaging aspect of the earthquake event.
Liquefaction occurs where ground water is near the surface in soils composed of sands and silts.
The soil temporarily loses strength and behaves as a viscous liquid. Structures can settle or tip in the liquefied soil or be ripped apart as the ground spreads laterally or flows. Flow failures can move over kilometers at speeds of tens of kilometers per hour. They usually develop in loose, saturated sand on slopes greater than five percent. When subsurface sand layers lose strength because of liquefaction, lateral spreading can occur in overlying sediments allowing them to move down even the gentlest slopes.