When building a house, regional
seismic hazard maps are used to find the best (or the worst) place to locate for
earthquake shaking. Although greatly confused with its sister,
seismic risk, seismic hazard is the study of expected earthquake ground motions at any point on the earth.
and its presumed northern extension, the
Rodgers Creek Fault Zone]]
The calculations for seismic hazard, first formulated by C. Allin Cornell in 1968, can be quite complex. First, the regional geology and seismology is examined for patterns (using seismometers and earthquake location). Zones of similar potential for seismicity are drawn. For example, the famous San Andreas Fault might be drawn as a long narrow zone. Zones in the continental interior (the site for intraplate earthquakes) would be drawn as broad areas, since causative faults are generally not identified.
Each zone is given properties associated with source potential: how many earthquakes per year, the maximum size of earthquakes (maximum magnitude), etc. Finally, the calculations require formulae that give the required hazard indicators for a given earthquake size and distance. For example, some districts prefer to use peak acceleration, others use peak velocity, and more sophisticated uses require response spectral ordinates.
The computer program then integrates over all the zones and produces probability curves for the key ground motion parameter. The final result gives you a 'chance' of exceeding a given value over a specified amount of time. Standard building codes for homeowners might be concerned with a 1 in 500 years chance, while nuclear plants look at the 10,000 year time frame. A longer-term seismic history can be obtained through paleoseismology. The results may be in the form of a ground response spectrum for use in seismic analysis.
More elaborate variations on the theme also look at the soil conditions. If you build on a soft swamp, you are likely to experience many times the ground motions than your neighbour on solid rock. The standard seismic hazard calculations become adjusted upwards if you are postulating characteristic earthquakes.
Areas with high ground motion due to soil conditions are also often subject to soil failure due to liquefaction. Soil failure can also occur due to earthquake-induced landslides in steep terrain. Large area landsliding can also occur on rather gentle slopes as was seen in the "Good Friday Earthquake" in Anchorage, Alaska, March 28, 1964.
See also
C. Allin Cornell
Earthquake engineering
Mitigation of seismic motion
Neotectonics
Seismic performance
Vibration control
References
External links
U.S. Geological Survey National Seismic Hazard Maps: http://earthquake.usgs.gov/research/hazmaps/
The Global Seismic Hazard map: http://www.seismo.ethz.ch/GSHAP/
Infrastructure Risk Research Project at The University of British Columbia, Vancouver, Canada
Seismic Risk Analysis using GIS: Evaluation of Structural Damage to Buildings and Loss Estimation
Category:Earthquake and seismic risk mitigation
![A portion of California Memorial Stadium with Panoramic Hill in the background. The Hayward Fault passes directly under the playing field of Memorial (nearly from goal post to goal post), [3] where right-lateral strike-slip motion is shifting the northeast half of the building to the southwest at a rate of 1.2 mm/yr](http://web.archive.org./web/20110302153548im_/http://cdn.wn.com/pd/81/cd/2352ea979c3846f64a713dad9bae_grande.jpg "A portion of California Memorial Stadium with Panoramic Hill in the background. The Hayward Fault passes directly under the playing field of Memorial (nearly from goal post to goal post), [3] where right-lateral strike-slip motion is shifting the northeast half of the building to the southwest at a rate of 1.2 mm/yr")
![A portion of California Memorial Stadium with Panoramic Hill in the background. The Hayward Fault passes directly under the playing field of Memorial (nearly from goal post to goal post), [3] where right-lateral strike-slip motion is shifting the northeast half of the building to the southwest at a rate of 1.2 mm/yr](http://web.archive.org./web/20110302153548im_/http://cdn.wn.com/pd/81/cd/2352ea979c3846f64a713dad9bae_thumb.jpg "A portion of California Memorial Stadium with Panoramic Hill in the background. The Hayward Fault passes directly under the playing field of Memorial (nearly from goal post to goal post), [3] where right-lateral strike-slip motion is shifting the northeast half of the building to the southwest at a rate of 1.2 mm/yr")
