Resilience Metrics for Multi-Hazard Environments

Abstract

The United Nations Office for Disaster Risk Reduction reported that the 2011 natural disasters, including the earthquake and tsunami that struck Japan, resulted in $366 billion in direct damages and 29,782 fatalities worldwide. The rational management of such reduction and recovery is facilitated by an appropriate definition of resilience and associated metrics. In this paper, a resilience definition is provided that meets a set of requirements with clear relationships to the metrics of the relevant abstract notions of reliability and risk. Those metrics also meet logically consistent requirements drawn from measure theory, and provide a sound basis for the development of effective decision-making tools for multi-hazard environments. A proposed resilience definition consistent with a 2013 presidential directive that lends itself for quantification is “is the persistence under uncertainty of a system’s performance in the face of disturbances.” Current definitions do not always lend themselves naturally and intuitively to the development of consistent resilience metrics with clear relationships to the most relevant metrics of the abstract notions of reliability and risk. For example, defining resilience by the operative word of ability does not set the measurement process on the appropriate tracks by focusing on the abilities rather than the outcomes of these abilities. The primary outcome of these abilities is the continuance of performance, including bouncing-back, characteristic that could be appropriately termed as performance persistence. Performance persistence would naturally set measurement in terms of availability of the performance or continuance of system’s states of normalcy. Subsequent sections of this paper provide metrics based on this definition that meet logically consistent requirements drawn partly from measure theory, and provide a sound basis for the development of effective decision-making tools for multi-hazard environments. 1. Background