Geotechnical factors often exert a major influence on damage patterns and loss of life in earthquake
events. For example, the localized patterns of heavy damage during the 1985 Mexico City and 1989 Loma
Prieta, California, earthquakes provide grave illustrations of the importance of understanding the seismic
response of deep clay deposits and loose, saturated sand deposits. The near failure of the Lower San
Fernando dam in 1971 due to liquefaction of the upstream shell materials is another grave reminder that
we must strive to understand the seismic response of critical earth structures. The characteristics and
distribution of earth materials at a project site significantly influence the characteristics of the earthquake
ground motions, and hence significantly influence the seismic response of the constructed facilities at a
site. Moreover, the composition and geometry of earth structures, such as earth dams and solid waste
landfills, significantly affect their seismic response. Geotechnical considerations therefore play an integral
role in the development of sound earthquake-resistant designs. In this chapter, geotechnical earthquake
engineering phenomena such as site-specific amplification, soil liquefaction, and seismic slope stability
are discussed. Case histories are used to illustrate how earthquakes affect engineered systems, and established,
simplified empirical procedures that assist engineers in assessing the effects of these phenomena
are presented. The field of earthquake engineering is quite complex, so the need for exercising engineering
judgment based on appropriate experience is emphasized.