×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Difference between MCE and PGA

Difference between MCE and PGA

Difference between MCE and PGA

(OP)
What exactly is the difference between MCE (maximum credible earthquake) and PGA (peak ground acceleration)? It's not clear to me from their definitions. How're their magnitudes determined?

Also, why is it that, generally, buildings are designed for PGA (eg. UBC recommneds effective PGA) where as MCE values are used in Bridge designs? Is it just a matter of choice or there is any technical rationality?

-thanks,
Rao.

RE: Difference between MCE and PGA

The MCE is the largest credible earthquake that appears to be possible along a recognised fault or within a geographically defined tectonic province under the presently known or presumed tectonic framework.  Thus no matter how long a return period you consider, the MCE represents the best guess at what would be the largest earthquake likely to occur.

The peak ground acceleration varies depending on the return period of the earthquake event.  That is, the pga of a 1:100 event is smaller than the pga of a 1:500 earthquake.  

The pga is got either from the accelerogram of an actual event = absolute peak value measured off the accelerogram or from the acceleration response spectrum for Period = 0 secs.  This is because the short period spectra represents the response of a very stiff single degree of freedom system and thus will follow the ground motion.

Important facilities such as major bridges/power stations etc are usually designed to survive the MCE because of their public utility and need to be operative after major earthquakes.  Hence the seismic loadings codes for these sorts of structures talk about MCE.

General buildings are usually designed to survive with damage an earhquake with a return period of around 1:500 years. In areas of the world that are not seismically active, a MCE could have a return period less than this and so that area's seismic loadings code should reflect this and only require design to a lesser event.
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources