p.2 there is a need to move beyond qualitative conceptualizations of disaster
resistance and resilience to more quantitative measures, both to better understand factors contributing to resilience and
to assess more systematically the potential contributions and benefits of various research activities. It is therefore
necessary to clearly define resilience, identify its dimensions, and find ways of measuring and quantifying those dimensions.
With this end in mind, the authors have developed both a conceptual framework and a set of measures that make it possible
to empirically determine the extent to which different units of analysis and systems are resilient. This paper outlines that
framework, discusses ways of quantifying system performance criteria, and uses a systems diagram to illustrate how resilience
can be improved through system assessment and modification
p.3 The notion of resilience is commonly used to denote both strength and
flexibility.
p.3 Resilience has been defined as "the capacity
to cope with unanticipated dangers after they have become manifest, learning to bounce back" (Wildavsky 1991, p.
77) and as "the ability of a system to withstand stresses of 'environmental loading' ... a fundamental quality found
in individuals, groups, organizations, and systems as a whole" (Horne and Orr 1998, p. 31). Focusing on earthquake
disasters and specifically on postdisaster response, Comfort (1999, p. 21) defines resilience as "the capacity to
adapt existing resources and skills to new situations and operating conditions." The term implies both the
ability to adjust to "normal" or anticipated levels of stress and to adapt to sudden shocks and extraordinary demands.
In the context of hazards, the concept can be thought of as spanning both pre-event measures that seek to prevent hazard-related
damage and losses and post-event strategies designed to cope with and minimize disaster impacts.
p.4 Resilience can be understood as the ability of the system to
reduce the chances of a shock, to absorb a shock if it occurs (abrupt reduction of performance) and to recover quickly after
a shock (re-establish normal performance). More specifically, a resilient system is one that shows the following:
•
Reduced failure probabilities
• Reduced consequences from failures, in terms of lives lost, damage, and negative
economic and social consequences
• Reduced time to recovery (restoration of a specific system or set of systems to
their "normal" level of performance)
p.8 A distinction is also made... between "ends" and "means" dimensions
of resilience. For example, robustness and rapidity are essentially the desired "ends" that are accomplished
through resiliency-enhancing measures and are the outcomes that more deeply affect decision makers and stakeholders. Redundancy
and resourcefulness are measures that define the "means" by which resilience can be improved. For example, resilience
can be enhanced by adding redundant elements to a system. All elements of resilience are important, but robustness
and rapidity are seen as being key in measuring system and community resilience
p.12 Without going through all the steps of the diagrams, key steps
include gathering information through monitoring, sensing, and other field activities; processing the information through
information models to determine system fragility (performance) with which the losses and the resilience performance are determined
based on distinct resilience performance criteria; and using estimations (based on post event prediction) or
evaluations (based on post-event data), decision support systems that consider the resiliency measures and targets,
and advanced technologies (for preparedness and/or recovery) to modify the facility system or community to enhance
resiliency as appropriate. The closed loops indicate that an iterative dynamic process is required to achieve
optimal response.
