Geotechnical Engineering 101 and more…

Building firm foundations

Earthquake prediction and structure safety

Posted by Kshitija Nadgouda on February 28, 2008

Predicting earthquakes has been very controversial subject. Seismologists can only predict that movement is “possible” along a certain fault line or it is imminent. The two aspects of the prediction – where and when – are not easy to determine. So typically, what seismologists give, are “forecasts” – not predictions. They give an estimated location, and time of an earthquake of possible magnitude.

So when structures are being built, one needs to study the “seismic hazards” that the structure will likely face. The seismic hazards that can affect a structure due to a nearby earthquake are classified as primary and secondary. Primary hazards includes ground rupture, while secondary hazards includes ground shaking, ground lurching, liquefaction, etc.

Ground rupture occurs at the surface of active faults. Since the location of a fault, deep within the earth may not be known accurately or since there may be several small faults at a given location, “fault hazard zones” are demarcated on the surface by geologists and seismologists. Any construction should be avoided within these zones.

Ground shaking occurs in all earthquake prone areas, and to mitigate the effects of shaking, all structures must be built and designed as per local building codes and using sound engineering judgment.

Since it is not practical and uneconomical to build structures that resist maximum possible earthquakes with minimum damage, the building codes typically follow a few principles. The Uniform Building Code (UBC) lays down the following requirements:

  • The structures should be able to resist minor earthquakes without damage
  • The structures should be able to resist moderate earthquakes without structural damage but with some nonstructural damage
  • The structures should be able to resist major earthquakes without collapse but with some structural as well as nonstructural damage.

Although this does not guarantee that severe structural damage will not occur, at least we can expect that the structure will not collapse.

Here are some interesting sites that talk about earthquake prediction:

Copyright Kshitija Nadgouda.

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5 Responses to “Earthquake prediction and structure safety”

  1. earthquakegirl said

    Another interesting site I’ve found about earthquake prediction is http://www.quakefinder.com
    They research earthquakes and monitor electromagnetic signal at various stations in California in hope of accurately forecasting earthquakes.

  2. italianopinionist said

    Why can’t science at least doubt about earthquakes’ forecast?

    We are used to weather forecast and we often trust them even when they fail. In what respect is Giuliani’s forecast so different?

    http://italianopinionist.wordpress.com/2009/04/09/why-cant-science-at-least-doubt-about-earthquakes-forecast/

  3. imhkki said

    For some retaining structures there are some papers geotextiles help the structure during earthquakes

  4. Dear Italinaopinionist:
    I don’t think that seismic forecast is impossible but it did not work until now.
    For example, in the 1970s and 80s, Japan created a program that emphasized prediction over mitigation. The expensive forecasting program failed to predict the earthquake which devastated the city of Kobe in 1995 and Japan changed the philosophy. Until nowadays, proper structural design and statistical analysis proved to be much more effective than all the forecasting efforts.

  5. In terms of construction, I believe that geological evaluation is important. It helps achieve correct design planning that is vital to earthquake risk prevention measures. If you need to find out more about geological evaluation, ask an environmental engineer. http://www.envirotech.com.au

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