The seismic design criteria applied to sitting commercial nuclear power plants operating in the U.S. received increased attention following the March 11th, 2011 earthquake and tsunami that devastated Japan's Fukushima Daiichi nuclear power station. Since the events, some in Congress have begun to question whether U.S. plants are vulnerable to a similar threat, particularly in light of the Nuclear Regulatory Commissions's (NRC)ongoing reassessment of seismic risks at certain plant sites. This book presents some of the general design concepts of operating nuclear power plants in order to discuss design considerations for seismic events.