Seismic risk refers to the risk of damage from earthquake to a building, system, or other entity. Seismic risk has been defined, for most management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a specified period of time. A building located in a region of high

seismic hazard A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and includ ...

is at lower risk if it is built to sound seismic engineering principles. On the other hand, a building located in a region with a history of minor seismicity, in a brick building located on fill subject to liquefaction can be as high or higher risk. A special subset is

urban seismic risk Urban seismic risk is a subset of the general term seismic risk which describes the problems specific to centers of population when they are subjected to earthquakes. Many risks can be minimized with good earthquake construction, and seismic an ...

which looks at the specific issues of cities. Risk determination and emergency response can also be determined through the use of an

Earthquake scenario Earthquake scenario is a planning tool to determine the appropriate emergency responses or building systems in areas exposed to earthquake hazards. It uses the basics of seismic hazard studies, but usually places a set earthquake on a specific fau ...

Determination of seismic risk

The determination of seismic risk is the foundation for risk mitigation decision-making, a key step in risk management. Large corporations and other enterprises (e.g., local governments) analyze their 'portfolio' of properties, to determine how to best allocate limited funds for structural strengthening of buildings, or other risk reduction measures such as emergency planning. In calculating the risk of each facility in the 'portfolio', potential life safety and economic losses due not only to structural damage, but also to equipment, contents and business interruption are considered. Public agencies (local, state governments and federal agencies) similarly analyze their portfolios. The interconnections of infrastructures such as water, road and highway, and electric power systems are also considered. Insurance companies routinely employ estimates of seismic risk in their operations to determine appropriate insurance rates, monitor over-accumulation of policies in a small area, and purchase reinsurance. A simplified method of calculating seismic risk for a given city, involves the use of a street survey. If you know the level of seismic hazard, the damage generally follows established patterns. Seismic risk is often determined using a seismic modeling computer programs which uses the seismic hazard inputs and combines them with the known susceptibilities of structures and facilities, such as buildings, bridges, electrical power switching stations, etc. The result gives probabilities for economic damage or casualties, for example the HAZUS computer program. While the results can be used as a general measure of seismic risk for types of buildings, the actual seismic risk for any individual building may vary considerably and will depend upon its exact configuration and condition. Acquiring and analyzing the specific data for an individual building or facility is one of the most expensive and daunting aspects of seismic risk estimation. Progress is made if one can calculate the 'fragility' or seismic capacity of the components within a structure. In 1999, ASTM produced guidelines for reporting seismic loss estimates on commercial properties, commonly known as Probable Maximum Loss or PML reviews. These guidelines specify the scope of work, qualifications of the reviewer, and proper nomenclature for reporting loss estimates.

Reduction of seismic risk

Seismic risk can be reduced by active programs that improve emergency response, and improve basic infrastructure. The concepts of

earthquake preparedness Earthquake preparedness is a set of measures taken at the individual, organisational and societal level to minimise the effects of an earthquake. Preparedness measures can range from securing heavy objects, structural modifications and storing suppl ...

can help plan for emergencies arising from an earthquake. Building codes are intended to help to manage seismic risk and are updated as more is learned about the effects of seismic

ground motion Ground motion is the movement of the earth's surface from earthquakes or explosions. Ground motion is produced by seismic waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the earth a ...

on buildings. This type of active improvement of mitigation of damage from earthquakes is known as

seismic retrofit Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent exp ...

. However, the changes generally do not immediately improve seismic risk in a community since existing buildings are rarely required to be upgraded to meet the revisions.

Notes

External links

* C. Allin Cornell
HAZUS
- Seismic Risk Program for the US
An All HAZUS Web Space HAZUS Community websiteInfrastructure Risk Research Project at The University of British Columbia, Vancouver, CanadaOIKOS
- Educational European project based on Google Maps Mashups
EMSC : Seismic real-time informationDiagnose the impact of global earthquakes from direct and indirect eyewitnesses contributions
{{Natural disasters Earthquake and seismic risk mitigation

Determination of seismic risk

Reduction of seismic risk

See also

Notes

External links