physical vulnerability) to disaster impacts (physical and social) in both chronological and social time. Second, research on these processes can be used to identify specific segments of threatened social systems that could suffer disaster impacts disproportionately, such as low-income households, ethnic minorities, or specific types of businesses (social vulnerability). Third, research on these processes can be used to identify disaster event-specific conditions (length of forewarning, predictability, controllability, and magnitude, scope, and duration of impact) that influence the level of disaster impacts. Fourth, findings on the interrelationships among characteristics of hazard vulnerability and disaster event characteristics allow documentation of the roles and interaction of pre-impact interventions (mitigation, emergency preparedness, and recovery preparedness practices) and post-impact responses (emergency and recovery activities) in influencing the level of disaster impacts. The causal processes by which disasters produce systemic effects in chronological and social time is informed generally within theorizing by Kreps (1985, 1989b) and Quarantelli (1989), and more specifically by causal models proposed by Cutter (1996), Lindell and Prater (2003), and Prater et al. (2004).

The preexisting conditions most directly relevant to disaster impacts are hazard exposure, physical vulnerability, and social vulnerability.

Hazard exposure is defined by the probability of occurrence (or, equivalently, the recurrence interval) of events of a given physical magnitude and scope occurring in different locations. Hazard exposure arises from people’s occupancy of geographical areas where they could be affected by extreme events that threaten their lives or property. Social scientists have made contributions to understanding hazard exposure principally by examining the distribution of hazardous conditions and the human occupancy of hazardous zones (Burton et al., 1993; Monmonier, 1997).

A major component of physical vulnerability is structural vulnerability, which arises when buildings are constructed using designs and materials that are incapable of resisting extreme energy levels (e.g., high wind, hydrodynamic pressures of water, seismic shaking) or that allow the infiltration of hazardous materials. Thus, structural vulnerability can be defined by the likelihood that an event of a given magnitude will cause various damage