[PLUG-TALK] The Big One

John Jason Jordan johnxj at comcast.net
Tue Mar 16 05:42:50 UTC 2010


On Mon, 15 Mar 2010 22:02:00 -0700
Keith Lofstrom <keithl at kl-ic.com> dijo:

>As near as I can tell (the literature is vague), building code for
>new construction is designed for minimal loss of life in a Richter 7. 
>California is 7.5 .  We get fewer earthquakes in Oregon, the "frequent"
>ones are mere Richter 5's to 7's.  But a megathrust Cascadia quake
>would be far larger than anything California has experienced
>historically. 

Portland area will get the effects from the Cascadia event, but at a
vastly reduced amount. We have our own fault lines, and they will shift
in sympathy with Cascadia, but not nearly as much. In other words, do
not assume that your house will experience a Richter 9 event. 

Rather than worry about the upcoming Cascadia event, research the
Portland area events for the past few hundred years. That is what you
should expect.

The problem is that no one knows exactly how much our local fault lines
will move in sympathy with Cascadia, and there has been less research
done on local geological evidence. However, the best minds on the
subject agree that it will not be a major catastrophe locally. Portland
building codes were adjusted ~20 years ago and those are what you would
be best advised to follow.

I have it on advice from various people in Portland building circles
that the big issue is the foundation. Nowadays foundations must have
lots of steel inside so they will move as a unit instead of breaking
into cobblestones. If your foundation is older than 20 years there is
not a lot you can do about it, outside of prayer. 

I recently tried to add earthquake insurance for my properties, and
discovered that the premiums were outrageous. Not that I have a lot of
respect for actuaries, but I wonder what the insurance companies know.

Having said all of that, if you live at the coast, move while property
values are still high.



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