Aftershocks instead of seismic events?

[Lion06]

Check out this story.

http://news.yahoo.com/s/livescience...recentmidwestquakescalledaftershocksfrom1800s

Does anyone believe this will have a bearing on seismic design for particular regions of the U.S. and work it's way into the IBC?

 

[JAE]

You mean like a lower seismic intensity in southern Illinois?

 

[msquared48]

To me, this is man's definition of a natural process - an attempt to put it in a box. A quake is a quake is a quake, and should be designed for as such.

Personally, I don't see that this changes anything. It is just someone's opinion and it may change tomorrow.

Mike McCann
MMC Engineering

 

[cvg]

For one thing, "there's no motion across the fault now, so nothing's going on, but yet there are still small earthquakes there," said Seth Stein

Quakes are caused by motion of a fault, yet the researcher seems to contradict this in his interview. He seems to imply that aftershocks are not truly earthquakes. I suspect this research will little effect on seismic design in the midwest. USGS published the following fact sheet which seems to dismiss Stein's idea.

http://pubs.usgs.gov/fs/2009/3071/

However, the USGS is doing some research that may be more promising.

http://earthquake.usgs.gov/regional/ceus/products/eq_sim/index.php

http://earthquake.usgs.gov/regional/ceus/products/velocity/index.php

 

[Lion06]

Here is another story on the study.

JAE, I did mean do you think this could result in lower seismic intensities to be designed for at some point in the future.

Mike, I agree that a seismic event is not something that can be neatly put into a box. It's all just approximations. As engineers, however, we have to design for something. I was just asking if anyone thought this study might result in that something being a little smaller.

 

[Lion06]

http://www.nature.com/news/2009/091104/full/news.2009.1062.html

Here's the story I meant to post in the last post. The USGS statement does seem to dismiss this as nonsense!

 

[msquared48]

Knowing the ultimate capacity of New Madrid, and all the other new, and reliable, information that has surfaced in the last few years. I do not know how any base design values can be lowered.

I think the only "lowering" achieved will be through technology to literally go with the flow of the force.

Resistance is futile...

Mike McCann
MMC Engineering

 

[msucog]

the maps have generally been lowered with each revision as we "better understand" the earth processes. the best we can do is use the nice and neat procedures that are in place and adjust as we learn. once the big one hits some day, the maps will likely be bumped up. notice one detail, ibc maps are not identical to the usgs maps...particularly on top of high seismic areas...so that it's not so outragously expensive to build something there and stunt development. same concept as building a house on the gulf...just waiting for the next big hurricane to wipe it out.