Earthquake considerations in House Hunting

 My wife and I are looking for a house/condo/apartment in the
South Bay Area of California.  We've some earthquake related
questions:

1. There's a 8-storage metropolitan apartment building that the
   builder claims to be built with post-tension construction.  It
   was built in early 2003.  Is this technique something especially
   for earthquake?  Or is it typical of any building these days,
   regardless of geographical locations.

2. Given the current construction methods, what's the safety profile
   of such a multi-level building versus the usual 2-3 story houses?

3. There're a lot of 40-50 year old houses selling at over half a
   million here due to school district.  My impression is that wood
   framed structure tends to age and become weaker.  Is this true?

Thanks,
Raymond

 

Are you new to California? If I had to guess I would say so. I doubt
the average California home buyer worries about any of this. Even the
best-built building is going to come down in a big earthquake in the
wrong location. The newer the building the more likely it meets updated
codes, of course. However, some old construction has proven to be very
sturdy as has survived many earthquakes. The only rule to know is to
avoid houses made of brick. Fortunately, 90%+ of housing here is wooden.
Other than that, I wouldn't too much worry about it. There's a good chance
you won't even *be* at home when an earthquake hits, but will be out and
about. The best-built home in the world won't help you if your office
building collapses on you. That's why I wouldn't worry about it too much.


Dimitri

 

construction.  It

especially

he has to follow the code for earthquake zones...it no doubt
meets the code... your interest should be how close is to
known major fault lines..if its close you are screwed
regardless.  If its a few miles away you will probably be fine
with current construciton.



profile

houses?

Depends on construction details.   Generally speaking its a
tiny fraction of the structures in an entire area that go
south in a disaster.  Id worry  about location on hillsides,
mudslides and fire and what the neigbors house might do in a
shake or fire etc.



that wood

The old wood is like iron compared to the new growth timber.
If its old and in good shape in this area its well built.
The foundation issues are more relevant to your questions.
You should get a house inspection before buying regardless.

and you need to look at the plus side..when california breaks
off into the pacific you could end up with island or beach
front property.  :)


Phil Scott

 ryeung@earthlink.net (Raymond Yeung) wrote:

Well, Raymond, I live in Indiana, where we don't worry much about earthquakes,
and so my opinion on this subject may be worth exactly what you're paying for
it... but it seems obvious to me that a 40-50 year old building that's still
standing has proven that it's able to withstand whatever quakes have occurred
in that area in the last 40-50 years. And some of those have been pretty big.

 In a previous post Doug Miller says...

This is a misconception that many people have.  It is entirely possible
that the structure has used up its "reserve" strength and will come
tumbling down in the next "Big One".  There isn't a building yet
designed that can withstand every seismic event.  The current
methodology uses a peak ground acceleration with a 10% probability of
exceedance in 50 years.

I just spent all of Saturday at a structural engineering seminar on the
seismic portion of the the new IBC2003.  This code is the state of the
art in terms of how SE's understand seismic events, but the code is only
as good as the design team who implements it and the builder who
constructs the building according to the design.

BTW, Indiana is not immune.  The SW corner of the state has some
relatively high seismic risk.

--
Bob Morrison
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA