PSN-L Email List Message

Subject: quake resistant buildings
From: sean@...........
Date: Sun, 28 Jan 2001 14:43:12 -0600 (CST)

Some further considerations about earthquake safe buildings:

Naturally if no one is there, a great quake just happens. We had
an M8.6 in the Aleutians in May of 86, and it did little damage to 
the militarily-constructed Navy base. We were lucky that our observer
was home at the time, since he was kept busy for several minutes
pushing the slide-mounted electronics units back into the equipment
racks in the observatory room (I had gotten negligent about locking

Of course, the safest plan is not to build on or near (20km) of
a known fault. This presumes that the geologists know where any
potentially active fault may lie (unlike the Northridge event).
It also presumes that the realtors don't control the zoning boards,
a-la most of California.  It also presumes that there is enough space
in a very populous country to build away from active zones.

And then there are the best laid plans of mice and men. At the time
of the last Mexico city disaster, strong building codes were in place,
but the newer the building was, the more it fell down. It turns out 
that bribery let the rebar count be less and the cement weaker. And 
in real poor countries, they would if they could, but they unfortunately 
need the housing and can't afford cement, so they just build with less,
like a 2-sack mortar mix (2 sacks of portland cement per cubic yard;
a 5-sack mix is the minimum); this is just enough to keep the rain
from washing the sand and gravel away. And as you see in the pictures 
of the present India disaster, there is not a lot of rebar in the rubble.

And the newer techniques seen in California (eg base isolation) are
very expensive, and even the survivable-failure designs (the building
doesn't collapse but is an economic loss) are expensive (lots of steel,
as is seen exposed in the retro-reinforced buildings in San Francisco),
and are untested in most of the world.

So there is lots of agreement about what can be done, but no one wants
to put their money where their mouth is and possibly prevent these
horrible casualties.


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Larry Cochrane <cochrane@..............>