Center for Extreme Load Effects on Structures


Risk assessment

The first step in boosting resilience to extreme events is understanding the hazards in a region and the potential consequences. First, the hazards must be determined. Then, the risk is calculated.

Example: Risk in the Charleston area

Related Links:

HAZUS loss estimation software from the Federal Emergency Management Agency

Virginia Tech Seismological Observatory (VTSO

Risk Analysis for Extreme Events: Economic Incentives for Reducing Future Losses by Howard Kunreuther, Robert Meyer and Christophe Van den Bulte

Hazard

A hazard is the likelihood or expected occurrence of an event. Hazards are often described as probabilities.

Scientists and engineers first determine the level of hazard in a region considering the following:

  • prior earthquakes, floods, tornados, hurricanes, and fires
  • the shape of the land (topography), the quality of soil, the water systems
  • land use: what has been built where and how that can increase or reduce the effects of the hazard

Risk

Risk is the chance of a hazard occurring and its expected consequences.

Risk can be described in dollars or casualties.

Risk is determined by analyzing how much a hazard could injure people, property, and economic survival. Questions are posed, such as:

  1. How will buildings perform? What is the probability they will fail?
  2. How will lifelines survive? Will bridges collapse? Will pipelines break? Will communications be maintained?
  3. What is the predicted cost to rebuild?
  4. How should human injury and loss of life be calculated?
  5. How long will a community or business need before it can operate?

Measuring risk

Measuring risk is never precise, because hazards are unpredictable and determining the future performance of structures and people is not exact. The imprecise and technical terms involved can increase the difficulty for community and business decision makers.

Hazards are typically determined by scientific and technical experts who give a range of probabilities. For example, a community may have a 1 in 10 chance of a category 5 hurricane in the next 50 years, or a 1 in 100 chance in 10 years.

Risks are often determined by teams of scientific and financial experts. Terms can include:

  • Reliability of a structure, which is the opposite of its probability of failure in specified conditions.
  • Performance per unit-dollar-expenditure.

CELES research, tools and experience:

Software for analyzing and predicting earthquake hazard and risk. This can be used for custom analysis.

Prediction and Geographical Information System (GIS) Mapping of Ground Motions and Site Response in Charleston, SC and Two Neighboring Counties: First Phase Development of a GIS for Seismic Hazard Evaluation

"Estimated Magnitudes and Ground Motions Characteristics Associated with Prehistoric Earthquakes in the Wabash Valley Region of the Central United States," (USGS)

"Wide-Angle Reflection and Potential Field Modeling of the Eastern Tennessee Seismic Zone", collaborative work involving Virginia Tech, University of North Carolina, Chapel Hill and University of Georgia (NSF)

Next: Risk Management: Decision Making